Merge branch 'development'

* development: (939 commits)
  Add asset-buyer to published packages section in README
  Publish
  Updated CHANGELOGS
  Update BuyQuote interface
  force re-build
  Add website build to instructions
  Revert format and re-add changes
  Build website in parallel with other tests since no other test relies on it being built to run
  Add back sourceMap support for both dev/prod
  Upgrade webpack
  Add missing default options
  Remove unused constants
  Add fee order with a takerFee
  Add additional order factory methods and refactor test to use them
  Add comments about buy quote calculation
  Update CHANGELOG
  Fix linter
  Add additional test for slippage
  Add buy_quote_calculator_test
  Add 0x Instant to bundle analysis
  ...

67 files changed, 2584 insertions, 1088 deletions

diff --git a/packages/contracts/src/2.0.0/examples/Whitelist/Whitelist.sol b/packages/contracts/src/2.0.0/examples/Whitelist/Whitelist.sol
index 60cac26ea..e4e25038c 100644
--- a/packages/contracts/src/2.0.0/examples/Whitelist/Whitelist.sol
+++ b/packages/contracts/src/2.0.0/examples/Whitelist/Whitelist.sol
@@ -37,7 +37,7 @@ contract Whitelist is
     bytes internal TX_ORIGIN_SIGNATURE;
     // solhint-enable var-name-mixedcase
 
-    byte constant internal VALIDATOR_SIGNATURE_BYTE = "\x06";
+    byte constant internal VALIDATOR_SIGNATURE_BYTE = "\x05";
 
     constructor (address _exchange)
         public
diff --git a/packages/contracts/src/2.0.0/forwarder/Forwarder.sol b/packages/contracts/src/2.0.0/extensions/Forwarder/Forwarder.sol
index 5b88b05b1..94dec40ed 100644
--- a/packages/contracts/src/2.0.0/forwarder/Forwarder.sol
+++ b/packages/contracts/src/2.0.0/extensions/Forwarder/Forwarder.sol
@@ -34,19 +34,14 @@ contract Forwarder is
     MixinExchangeWrapper,
     MixinForwarderCore
 {
-
     constructor (
         address _exchange,
-        address _etherToken,
-        address _zrxToken,
         bytes memory _zrxAssetData,
         bytes memory _wethAssetData
     )
         public
         LibConstants(
             _exchange,
-            _etherToken,
-            _zrxToken,
             _zrxAssetData,
             _wethAssetData
         )
diff --git a/packages/contracts/src/2.0.0/forwarder/MixinAssets.sol b/packages/contracts/src/2.0.0/extensions/Forwarder/MixinAssets.sol
index e06f9a8e3..43efb5ff3 100644
--- a/packages/contracts/src/2.0.0/forwarder/MixinAssets.sol
+++ b/packages/contracts/src/2.0.0/extensions/Forwarder/MixinAssets.sol
@@ -18,10 +18,10 @@
 
 pragma solidity 0.4.24;
 
-import "../utils/LibBytes/LibBytes.sol";
-import "../utils/Ownable/Ownable.sol";
-import "../tokens/ERC20Token/IERC20Token.sol";
-import "../tokens/ERC721Token/IERC721Token.sol";
+import "../../utils/LibBytes/LibBytes.sol";
+import "../../utils/Ownable/Ownable.sol";
+import "../../tokens/ERC20Token/IERC20Token.sol";
+import "../../tokens/ERC721Token/IERC721Token.sol";
 import "./libs/LibConstants.sol";
 import "./mixins/MAssets.sol";
 
@@ -31,7 +31,6 @@ contract MixinAssets is
     LibConstants,
     MAssets
 {
-
     using LibBytes for bytes;
 
     bytes4 constant internal ERC20_TRANSFER_SELECTOR = bytes4(keccak256("transfer(address,uint256)"));
@@ -67,7 +66,7 @@ contract MixinAssets is
         } else if (proxyId == ERC721_DATA_ID) {
             transferERC721Token(assetData, amount);
         } else {
-            revert("UNSUPPORTED_TOKEN_PROXY");
+            revert("UNSUPPORTED_ASSET_PROXY");
         }
     }
 
diff --git a/packages/contracts/src/2.0.0/forwarder/MixinExchangeWrapper.sol b/packages/contracts/src/2.0.0/extensions/Forwarder/MixinExchangeWrapper.sol
index 4584bb840..fea9a53c2 100644
--- a/packages/contracts/src/2.0.0/forwarder/MixinExchangeWrapper.sol
+++ b/packages/contracts/src/2.0.0/extensions/Forwarder/MixinExchangeWrapper.sol
@@ -21,10 +21,10 @@ pragma experimental ABIEncoderV2;
 
 import "./libs/LibConstants.sol";
 import "./mixins/MExchangeWrapper.sol";
-import "../protocol/Exchange/libs/LibAbiEncoder.sol";
-import "../protocol/Exchange/libs/LibOrder.sol";
-import "../protocol/Exchange/libs/LibFillResults.sol";
-import "../protocol/Exchange/libs/LibMath.sol";
+import "../../protocol/Exchange/libs/LibAbiEncoder.sol";
+import "../../protocol/Exchange/libs/LibOrder.sol";
+import "../../protocol/Exchange/libs/LibFillResults.sol";
+import "../../protocol/Exchange/libs/LibMath.sol";
 
 
 contract MixinExchangeWrapper is
@@ -34,7 +34,6 @@ contract MixinExchangeWrapper is
     LibConstants,
     MExchangeWrapper
 {
-
     /// @dev Fills the input order.
     ///      Returns false if the transaction would otherwise revert.
     /// @param order Order struct containing order specifications.
@@ -61,7 +60,7 @@ contract MixinExchangeWrapper is
         // Call `fillOrder` and handle any exceptions gracefully
         assembly {
             let success := call(
-                gas,                                // forward all gas, TODO: look into gas consumption of assert/throw
+                gas,                                // forward all gas
                 exchange,                           // call address of Exchange contract
                 0,                                  // transfer 0 wei
                 add(fillOrderCalldata, 32),         // pointer to start of input (skip array length in first 32 bytes)
@@ -69,20 +68,14 @@ contract MixinExchangeWrapper is
                 fillOrderCalldata,                  // write output over input
                 128                                 // output size is 128 bytes
             )
-            switch success
-            case 0 {
-                mstore(fillResults, 0)
-                mstore(add(fillResults, 32), 0)
-                mstore(add(fillResults, 64), 0)
-                mstore(add(fillResults, 96), 0)
-            }
-            case 1 {
+            if success {
                 mstore(fillResults, mload(fillOrderCalldata))
                 mstore(add(fillResults, 32), mload(add(fillOrderCalldata, 32)))
                 mstore(add(fillResults, 64), mload(add(fillOrderCalldata, 64)))
                 mstore(add(fillResults, 96), mload(add(fillOrderCalldata, 96)))
             }
         }
+        // fillResults values will be 0 by default if call was unsuccessful
         return fillResults;
     }
 
@@ -163,7 +156,7 @@ contract MixinExchangeWrapper is
 
             // Convert the remaining amount of makerAsset to buy into remaining amount
             // of takerAsset to sell, assuming entire amount can be sold in the current order
-            uint256 remainingTakerAssetFillAmount = getPartialAmount(
+            uint256 remainingTakerAssetFillAmount = getPartialAmountFloor(
                 orders[i].takerAssetAmount,
                 orders[i].makerAssetAmount,
                 remainingMakerAssetFillAmount
@@ -231,7 +224,7 @@ contract MixinExchangeWrapper is
 
             // Convert the remaining amount of ZRX to buy into remaining amount
             // of WETH to sell, assuming entire amount can be sold in the current order.
-            uint256 remainingWethSellAmount = getPartialAmount(
+            uint256 remainingWethSellAmount = getPartialAmountFloor(
                 orders[i].takerAssetAmount,
                 safeSub(orders[i].makerAssetAmount, orders[i].takerFee),  // our exchange rate after fees 
                 remainingZrxBuyAmount
diff --git a/packages/contracts/src/2.0.0/forwarder/MixinForwarderCore.sol b/packages/contracts/src/2.0.0/extensions/Forwarder/MixinForwarderCore.sol
index 93cbf79be..54487f726 100644
--- a/packages/contracts/src/2.0.0/forwarder/MixinForwarderCore.sol
+++ b/packages/contracts/src/2.0.0/extensions/Forwarder/MixinForwarderCore.sol
@@ -24,10 +24,10 @@ import "./mixins/MWeth.sol";
 import "./mixins/MAssets.sol";
 import "./mixins/MExchangeWrapper.sol";
 import "./interfaces/IForwarderCore.sol";
-import "../utils/LibBytes/LibBytes.sol";
-import "../protocol/Exchange/libs/LibOrder.sol";
-import "../protocol/Exchange/libs/LibFillResults.sol";
-import "../protocol/Exchange/libs/LibMath.sol";
+import "../../utils/LibBytes/LibBytes.sol";
+import "../../protocol/Exchange/libs/LibOrder.sol";
+import "../../protocol/Exchange/libs/LibFillResults.sol";
+import "../../protocol/Exchange/libs/LibMath.sol";
 
 
 contract MixinForwarderCore is
@@ -39,7 +39,6 @@ contract MixinForwarderCore is
     MExchangeWrapper,
     IForwarderCore
 {
-
     using LibBytes for bytes;
 
     /// @dev Constructor approves ERC20 proxy to transfer ZRX and WETH on this contract's behalf.
@@ -47,10 +46,12 @@ contract MixinForwarderCore is
         public
     {
         address proxyAddress = EXCHANGE.getAssetProxy(ERC20_DATA_ID);
-        if (proxyAddress != address(0)) {
-            ETHER_TOKEN.approve(proxyAddress, MAX_UINT);
-            ZRX_TOKEN.approve(proxyAddress, MAX_UINT);
-        }
+        require(
+            proxyAddress != address(0),
+            "UNREGISTERED_ASSET_PROXY"
+        );
+        ETHER_TOKEN.approve(proxyAddress, MAX_UINT);
+        ZRX_TOKEN.approve(proxyAddress, MAX_UINT);
     }
 
     /// @dev Purchases as much of orders' makerAssets as possible by selling up to 95% of transaction's ETH value.
@@ -87,7 +88,7 @@ contract MixinForwarderCore is
         uint256 makerAssetAmountPurchased;
         if (orders[0].makerAssetData.equals(ZRX_ASSET_DATA)) {
             // Calculate amount of WETH that won't be spent on ETH fees.
-            wethSellAmount = getPartialAmount(
+            wethSellAmount = getPartialAmountFloor(
                 PERCENTAGE_DENOMINATOR,
                 safeAdd(PERCENTAGE_DENOMINATOR, feePercentage),
                 msg.value
@@ -103,7 +104,7 @@ contract MixinForwarderCore is
             makerAssetAmountPurchased = safeSub(orderFillResults.makerAssetFilledAmount, orderFillResults.takerFeePaid);
         } else {
             // 5% of WETH is reserved for filling feeOrders and paying feeRecipient.
-            wethSellAmount = getPartialAmount(
+            wethSellAmount = getPartialAmountFloor(
                 MAX_WETH_FILL_PERCENTAGE,
                 PERCENTAGE_DENOMINATOR,
                 msg.value
diff --git a/packages/contracts/src/2.0.0/forwarder/MixinWeth.sol b/packages/contracts/src/2.0.0/extensions/Forwarder/MixinWeth.sol
index e07940776..d2814a49b 100644
--- a/packages/contracts/src/2.0.0/forwarder/MixinWeth.sol
+++ b/packages/contracts/src/2.0.0/extensions/Forwarder/MixinWeth.sol
@@ -18,7 +18,7 @@
 
 pragma solidity 0.4.24;
 
-import "../protocol/Exchange/libs/LibMath.sol";
+import "../../protocol/Exchange/libs/LibMath.sol";
 import "./libs/LibConstants.sol";
 import "./mixins/MWeth.sol";
 
@@ -28,7 +28,6 @@ contract MixinWeth is
     LibConstants,
     MWeth
 {
-
     /// @dev Default payabale function, this allows us to withdraw WETH
     function ()
         public
@@ -82,7 +81,7 @@ contract MixinWeth is
         uint256 wethRemaining = safeSub(msg.value, wethSold);
 
         // Calculate ETH fee to pay to feeRecipient.
-        uint256 ethFee = getPartialAmount(
+        uint256 ethFee = getPartialAmountFloor(
             feePercentage,
             PERCENTAGE_DENOMINATOR,
             wethSoldExcludingFeeOrders
diff --git a/packages/contracts/src/2.0.0/forwarder/interfaces/IAssets.sol b/packages/contracts/src/2.0.0/extensions/Forwarder/interfaces/IAssets.sol
index 1e034c003..1e034c003 100644
--- a/packages/contracts/src/2.0.0/forwarder/interfaces/IAssets.sol
+++ b/packages/contracts/src/2.0.0/extensions/Forwarder/interfaces/IAssets.sol
diff --git a/packages/contracts/src/2.0.0/forwarder/interfaces/IForwarder.sol b/packages/contracts/src/2.0.0/extensions/Forwarder/interfaces/IForwarder.sol
index f5a26e2ba..f5a26e2ba 100644
--- a/packages/contracts/src/2.0.0/forwarder/interfaces/IForwarder.sol
+++ b/packages/contracts/src/2.0.0/extensions/Forwarder/interfaces/IForwarder.sol
diff --git a/packages/contracts/src/2.0.0/forwarder/interfaces/IForwarderCore.sol b/packages/contracts/src/2.0.0/extensions/Forwarder/interfaces/IForwarderCore.sol
index 3ecbb133b..74c7da01d 100644
--- a/packages/contracts/src/2.0.0/forwarder/interfaces/IForwarderCore.sol
+++ b/packages/contracts/src/2.0.0/extensions/Forwarder/interfaces/IForwarderCore.sol
@@ -19,8 +19,8 @@
 pragma solidity 0.4.24;
 pragma experimental ABIEncoderV2;
 
-import "../../protocol/Exchange/libs/LibOrder.sol";
-import "../../protocol/Exchange/libs/LibFillResults.sol";
+import "../../../protocol/Exchange/libs/LibOrder.sol";
+import "../../../protocol/Exchange/libs/LibFillResults.sol";
 
 
 contract IForwarderCore {
diff --git a/packages/contracts/src/2.0.0/forwarder/libs/LibConstants.sol b/packages/contracts/src/2.0.0/extensions/Forwarder/libs/LibConstants.sol
index c26d7902c..704e42ce3 100644
--- a/packages/contracts/src/2.0.0/forwarder/libs/LibConstants.sol
+++ b/packages/contracts/src/2.0.0/extensions/Forwarder/libs/LibConstants.sol
@@ -18,13 +18,16 @@
 
 pragma solidity 0.4.24;
 
-import "../../protocol/Exchange/interfaces/IExchange.sol";
-import "../../tokens/EtherToken/IEtherToken.sol";
-import "../../tokens/ERC20Token/IERC20Token.sol";
+import "../../../utils/LibBytes/LibBytes.sol";
+import "../../../protocol/Exchange/interfaces/IExchange.sol";
+import "../../../tokens/EtherToken/IEtherToken.sol";
+import "../../../tokens/ERC20Token/IERC20Token.sol";
 
 
 contract LibConstants {
 
+    using LibBytes for bytes;
+
     bytes4 constant internal ERC20_DATA_ID = bytes4(keccak256("ERC20Token(address)"));
     bytes4 constant internal ERC721_DATA_ID = bytes4(keccak256("ERC721Token(address,uint256)"));
     uint256 constant internal MAX_UINT = 2**256 - 1;
@@ -42,17 +45,18 @@ contract LibConstants {
 
     constructor (
         address _exchange,
-        address _etherToken,
-        address _zrxToken,
         bytes memory _zrxAssetData,
         bytes memory _wethAssetData
     )
         public
     {
         EXCHANGE = IExchange(_exchange);
-        ETHER_TOKEN = IEtherToken(_etherToken);
-        ZRX_TOKEN = IERC20Token(_zrxToken);
         ZRX_ASSET_DATA = _zrxAssetData;
         WETH_ASSET_DATA = _wethAssetData;
+
+        address etherToken = _wethAssetData.readAddress(16);
+        address zrxToken = _zrxAssetData.readAddress(16);
+        ETHER_TOKEN = IEtherToken(etherToken);
+        ZRX_TOKEN = IERC20Token(zrxToken);
     }
 }
diff --git a/packages/contracts/src/2.0.0/forwarder/libs/LibForwarderErrors.sol b/packages/contracts/src/2.0.0/extensions/Forwarder/libs/LibForwarderErrors.sol
index cdfb77a0b..fb3ade1db 100644
--- a/packages/contracts/src/2.0.0/forwarder/libs/LibForwarderErrors.sol
+++ b/packages/contracts/src/2.0.0/extensions/Forwarder/libs/LibForwarderErrors.sol
@@ -27,7 +27,7 @@ contract LibForwarderErrors {
     string constant OVERSOLD_WETH = "OVERSOLD_WETH";                                              // More WETH sold than provided with current message call.
     string constant COMPLETE_FILL_FAILED = "COMPLETE_FILL_FAILED";                                // Desired purchase amount not completely filled (required for ZRX fees only).
     string constant TRANSFER_FAILED = "TRANSFER_FAILED";                                          // Asset transfer failed.
-    string constant UNSUPPORTED_TOKEN_PROXY = "UNSUPPORTED_TOKEN_PROXY";                          // Proxy in assetData not supported.
+    string constant UNSUPPORTED_ASSET_PROXY = "UNSUPPORTED_ASSET_PROXY";                          // Proxy in assetData not supported.
     string constant DEFAULT_FUNCTION_WETH_CONTRACT_ONLY = "DEFAULT_FUNCTION_WETH_CONTRACT_ONLY";  // Fallback function may only be used for WETH withdrawals.
     string constant INVALID_MSG_VALUE = "INVALID_MSG_VALUE";                                      // msg.value must be greater than 0.
     string constant INVALID_AMOUNT = "INVALID_AMOUNT";                                            // Amount must equal 1.
diff --git a/packages/contracts/src/2.0.0/forwarder/mixins/MAssets.sol b/packages/contracts/src/2.0.0/extensions/Forwarder/mixins/MAssets.sol
index 83636432a..9e7f80d97 100644
--- a/packages/contracts/src/2.0.0/forwarder/mixins/MAssets.sol
+++ b/packages/contracts/src/2.0.0/extensions/Forwarder/mixins/MAssets.sol
@@ -24,7 +24,6 @@ import "../interfaces/IAssets.sol";
 contract MAssets is
     IAssets
 {
-
     /// @dev Transfers given amount of asset to sender.
     /// @param assetData Byte array encoded for the respective asset proxy.
     /// @param amount Amount of asset to transfer to sender.
diff --git a/packages/contracts/src/2.0.0/forwarder/mixins/MExchangeWrapper.sol b/packages/contracts/src/2.0.0/extensions/Forwarder/mixins/MExchangeWrapper.sol
index 360dea0e4..13c26b03a 100644
--- a/packages/contracts/src/2.0.0/forwarder/mixins/MExchangeWrapper.sol
+++ b/packages/contracts/src/2.0.0/extensions/Forwarder/mixins/MExchangeWrapper.sol
@@ -19,8 +19,8 @@
 pragma solidity 0.4.24;
 pragma experimental ABIEncoderV2;
 
-import "../../protocol/Exchange/libs/LibOrder.sol";
-import "../../protocol/Exchange/libs/LibFillResults.sol";
+import "../../../protocol/Exchange/libs/LibOrder.sol";
+import "../../../protocol/Exchange/libs/LibFillResults.sol";
 
 
 contract MExchangeWrapper {
diff --git a/packages/contracts/src/2.0.0/forwarder/mixins/MWeth.sol b/packages/contracts/src/2.0.0/extensions/Forwarder/mixins/MWeth.sol
index 88e77be4e..88e77be4e 100644
--- a/packages/contracts/src/2.0.0/forwarder/mixins/MWeth.sol
+++ b/packages/contracts/src/2.0.0/extensions/Forwarder/mixins/MWeth.sol
diff --git a/packages/contracts/src/2.0.0/extensions/OrderValidator/OrderValidator.sol b/packages/contracts/src/2.0.0/extensions/OrderValidator/OrderValidator.sol
new file mode 100644
index 000000000..8bfde3847
--- /dev/null
+++ b/packages/contracts/src/2.0.0/extensions/OrderValidator/OrderValidator.sol
@@ -0,0 +1,218 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity 0.4.24;
+pragma experimental ABIEncoderV2;
+
+import "../../protocol/Exchange/interfaces/IExchange.sol";
+import "../../protocol/Exchange/libs/LibOrder.sol";
+import "../../tokens/ERC20Token/IERC20Token.sol";
+import "../../tokens/ERC721Token/IERC721Token.sol";
+import "../../utils/LibBytes/LibBytes.sol";
+
+
+contract OrderValidator {
+
+    using LibBytes for bytes;
+
+    bytes4 constant internal ERC20_DATA_ID = bytes4(keccak256("ERC20Token(address)"));
+    bytes4 constant internal ERC721_DATA_ID = bytes4(keccak256("ERC721Token(address,uint256)"));
+
+    struct TraderInfo {
+        uint256 makerBalance;       // Maker's balance of makerAsset
+        uint256 makerAllowance;     // Maker's allowance to corresponding AssetProxy
+        uint256 takerBalance;       // Taker's balance of takerAsset
+        uint256 takerAllowance;     // Taker's allowance to corresponding AssetProxy
+        uint256 makerZrxBalance;    // Maker's balance of ZRX
+        uint256 makerZrxAllowance;  // Maker's allowance of ZRX to ERC20Proxy
+        uint256 takerZrxBalance;    // Taker's balance of ZRX
+        uint256 takerZrxAllowance;  // Taker's allowance of ZRX to ERC20Proxy
+    }
+
+    // solhint-disable var-name-mixedcase
+    IExchange internal EXCHANGE;
+    bytes internal ZRX_ASSET_DATA;
+    // solhint-enable var-name-mixedcase
+
+    constructor (address _exchange, bytes memory _zrxAssetData)
+        public
+    {
+        EXCHANGE = IExchange(_exchange);
+        ZRX_ASSET_DATA = _zrxAssetData;
+    }
+
+    /// @dev Fetches information for order and maker/taker of order.
+    /// @param order The order structure.
+    /// @param takerAddress Address that will be filling the order.
+    /// @return OrderInfo and TraderInfo instances for given order.
+    function getOrderAndTraderInfo(LibOrder.Order memory order, address takerAddress)
+        public
+        view
+        returns (LibOrder.OrderInfo memory orderInfo, TraderInfo memory traderInfo)
+    {
+        orderInfo = EXCHANGE.getOrderInfo(order);
+        traderInfo = getTraderInfo(order, takerAddress);
+        return (orderInfo, traderInfo);
+    }
+
+    /// @dev Fetches information for all passed in orders and the makers/takers of each order.
+    /// @param orders Array of order specifications.
+    /// @param takerAddresses Array of taker addresses corresponding to each order.
+    /// @return Arrays of OrderInfo and TraderInfo instances that correspond to each order.
+    function getOrdersAndTradersInfo(LibOrder.Order[] memory orders, address[] memory takerAddresses)
+        public
+        view
+        returns (LibOrder.OrderInfo[] memory ordersInfo, TraderInfo[] memory tradersInfo)
+    {
+        ordersInfo = EXCHANGE.getOrdersInfo(orders);
+        tradersInfo = getTradersInfo(orders, takerAddresses);
+        return (ordersInfo, tradersInfo);
+    }
+
+    /// @dev Fetches balance and allowances for maker and taker of order.
+    /// @param order The order structure.
+    /// @param takerAddress Address that will be filling the order.
+    /// @return Balances and allowances of maker and taker of order.
+    function getTraderInfo(LibOrder.Order memory order, address takerAddress)
+        public
+        view
+        returns (TraderInfo memory traderInfo)
+    {
+        (traderInfo.makerBalance, traderInfo.makerAllowance) = getBalanceAndAllowance(order.makerAddress, order.makerAssetData);
+        (traderInfo.takerBalance, traderInfo.takerAllowance) = getBalanceAndAllowance(takerAddress, order.takerAssetData);
+        bytes memory zrxAssetData = ZRX_ASSET_DATA;
+        (traderInfo.makerZrxBalance, traderInfo.makerZrxAllowance) = getBalanceAndAllowance(order.makerAddress, zrxAssetData);
+        (traderInfo.takerZrxBalance, traderInfo.takerZrxAllowance) = getBalanceAndAllowance(takerAddress, zrxAssetData);
+        return traderInfo;
+    }
+
+    /// @dev Fetches balances and allowances of maker and taker for each provided order.
+    /// @param orders Array of order specifications.
+    /// @param takerAddresses Array of taker addresses corresponding to each order.
+    /// @return Array of balances and allowances for maker and taker of each order.
+    function getTradersInfo(LibOrder.Order[] memory orders, address[] memory takerAddresses)
+        public
+        view
+        returns (TraderInfo[] memory)
+    {
+        uint256 ordersLength = orders.length;
+        TraderInfo[] memory tradersInfo = new TraderInfo[](ordersLength);
+        for (uint256 i = 0; i != ordersLength; i++) {
+            tradersInfo[i] = getTraderInfo(orders[i], takerAddresses[i]);
+        }
+        return tradersInfo;
+    }
+
+    /// @dev Fetches token balances and allowances of an address to given assetProxy. Supports ERC20 and ERC721.
+    /// @param target Address to fetch balances and allowances of.
+    /// @param assetData Encoded data that can be decoded by a specified proxy contract when transferring asset.
+    /// @return Balance of asset and allowance set to given proxy of asset.
+    ///         For ERC721 tokens, these values will always be 1 or 0.
+    function getBalanceAndAllowance(address target, bytes memory assetData)
+        public
+        view
+        returns (uint256 balance, uint256 allowance)
+    {
+        bytes4 assetProxyId = assetData.readBytes4(0);
+        address token = assetData.readAddress(16);
+        address assetProxy = EXCHANGE.getAssetProxy(assetProxyId);
+
+        if (assetProxyId == ERC20_DATA_ID) {
+            // Query balance
+            balance = IERC20Token(token).balanceOf(target);
+
+            // Query allowance
+            allowance = IERC20Token(token).allowance(target, assetProxy);
+        } else if (assetProxyId == ERC721_DATA_ID) {
+            uint256 tokenId = assetData.readUint256(36);
+
+            // Query owner of tokenId
+            address owner = getERC721TokenOwner(token, tokenId);
+
+            // Set balance to 1 if tokenId is owned by target
+            balance = target == owner ? 1 : 0;
+
+            // Check if ERC721Proxy is approved to spend tokenId
+            bool isApproved = IERC721Token(token).isApprovedForAll(target, assetProxy) || IERC721Token(token).getApproved(tokenId) == assetProxy;
+            
+            // Set alowance to 1 if ERC721Proxy is approved to spend tokenId
+            allowance = isApproved ? 1 : 0;
+        } else {
+            revert("UNSUPPORTED_ASSET_PROXY");
+        }
+        return (balance, allowance);
+    }
+
+    /// @dev Fetches token balances and allowances of an address for each given assetProxy. Supports ERC20 and ERC721.
+    /// @param target Address to fetch balances and allowances of.
+    /// @param assetData Array of encoded byte arrays that can be decoded by a specified proxy contract when transferring asset.
+    /// @return Balances and allowances of assets.
+    ///         For ERC721 tokens, these values will always be 1 or 0.
+    function getBalancesAndAllowances(address target, bytes[] memory assetData)
+        public
+        view
+        returns (uint256[] memory, uint256[] memory)
+    {
+        uint256 length = assetData.length;
+        uint256[] memory balances = new uint256[](length);
+        uint256[] memory allowances = new uint256[](length);
+        for (uint256 i = 0; i != length; i++) {
+            (balances[i], allowances[i]) = getBalanceAndAllowance(target, assetData[i]);
+        }
+        return (balances, allowances);
+    }
+
+    /// @dev Calls `token.ownerOf(tokenId)`, but returns a null owner instead of reverting on an unowned token.
+    /// @param token Address of ERC721 token.
+    /// @param tokenId The identifier for the specific NFT.
+    /// @return Owner of tokenId or null address if unowned.
+    function getERC721TokenOwner(address token, uint256 tokenId)
+        public
+        view
+        returns (address owner)
+    {
+        assembly {
+            // load free memory pointer
+            let cdStart := mload(64)
+
+            // bytes4(keccak256(ownerOf(uint256))) = 0x6352211e
+            mstore(cdStart, 0x6352211e00000000000000000000000000000000000000000000000000000000)
+            mstore(add(cdStart, 4), tokenId)
+
+            // staticcall `ownerOf(tokenId)`
+            // `ownerOf` will revert if tokenId is not owned
+            let success := staticcall(
+                gas,      // forward all gas
+                token,    // call token contract
+                cdStart,  // start of calldata
+                36,       // length of input is 36 bytes
+                cdStart,  // write output over input
+                32        // size of output is 32 bytes
+            )
+
+            // Success implies that tokenId is owned
+            // Copy owner from return data if successful
+            if success {
+                owner := mload(cdStart)
+            }    
+        }
+
+        // Owner initialized to address(0), no need to modify if call is unsuccessful
+        return owner;
+    }
+}
diff --git a/packages/contracts/src/2.0.0/multisig/MultiSigWallet.sol b/packages/contracts/src/2.0.0/multisig/MultiSigWallet.sol
index eb54fe047..516e7391c 100644
--- a/packages/contracts/src/2.0.0/multisig/MultiSigWallet.sol
+++ b/packages/contracts/src/2.0.0/multisig/MultiSigWallet.sol
@@ -1,13 +1,14 @@
 // solhint-disable
-pragma solidity ^0.4.10;
+pragma solidity ^0.4.15;
 
 
 /// @title Multisignature wallet - Allows multiple parties to agree on transactions before execution.
 /// @author Stefan George - <stefan.george@consensys.net>
 contract MultiSigWallet {
 
-    uint constant public MAX_OWNER_COUNT = 50;
-
+    /*
+     *  Events
+     */
     event Confirmation(address indexed sender, uint indexed transactionId);
     event Revocation(address indexed sender, uint indexed transactionId);
     event Submission(uint indexed transactionId);
@@ -18,6 +19,14 @@ contract MultiSigWallet {
     event OwnerRemoval(address indexed owner);
     event RequirementChange(uint required);
 
+    /*
+     *  Constants
+     */
+    uint constant public MAX_OWNER_COUNT = 50;
+
+    /*
+     *  Storage
+     */
     mapping (uint => Transaction) public transactions;
     mapping (uint => mapping (address => bool)) public confirmations;
     mapping (address => bool) public isOwner;
@@ -32,60 +41,54 @@ contract MultiSigWallet {
         bool executed;
     }
 
+    /*
+     *  Modifiers
+     */
     modifier onlyWallet() {
-        if (msg.sender != address(this))
-            throw;
+        require(msg.sender == address(this));
         _;
     }
 
     modifier ownerDoesNotExist(address owner) {
-        if (isOwner[owner])
-            throw;
+        require(!isOwner[owner]);
         _;
     }
 
     modifier ownerExists(address owner) {
-        if (!isOwner[owner])
-            throw;
+        require(isOwner[owner]);
         _;
     }
 
     modifier transactionExists(uint transactionId) {
-        if (transactions[transactionId].destination == 0)
-            throw;
+        require(transactions[transactionId].destination != 0);
         _;
     }
 
     modifier confirmed(uint transactionId, address owner) {
-        if (!confirmations[transactionId][owner])
-            throw;
+        require(confirmations[transactionId][owner]);
         _;
     }
 
     modifier notConfirmed(uint transactionId, address owner) {
-        if (confirmations[transactionId][owner])
-            throw;
+        require(!confirmations[transactionId][owner]);
         _;
     }
 
     modifier notExecuted(uint transactionId) {
-        if (transactions[transactionId].executed)
-            throw;
+        require(!transactions[transactionId].executed);
         _;
     }
 
     modifier notNull(address _address) {
-        if (_address == 0)
-            throw;
+        require(_address != 0);
         _;
     }
 
     modifier validRequirement(uint ownerCount, uint _required) {
-        if (   ownerCount > MAX_OWNER_COUNT
-            || _required > ownerCount
-            || _required == 0
-            || ownerCount == 0)
-            throw;
+        require(ownerCount <= MAX_OWNER_COUNT
+            && _required <= ownerCount
+            && _required != 0
+            && ownerCount != 0);
         _;
     }
 
@@ -108,8 +111,7 @@ contract MultiSigWallet {
         validRequirement(_owners.length, _required)
     {
         for (uint i=0; i<_owners.length; i++) {
-            if (isOwner[_owners[i]] || _owners[i] == 0)
-                throw;
+            require(!isOwner[_owners[i]] && _owners[i] != 0);
             isOwner[_owners[i]] = true;
         }
         owners = _owners;
@@ -151,7 +153,7 @@ contract MultiSigWallet {
 
     /// @dev Allows to replace an owner with a new owner. Transaction has to be sent by wallet.
     /// @param owner Address of owner to be replaced.
-    /// @param owner Address of new owner.
+    /// @param newOwner Address of new owner.
     function replaceOwner(address owner, address newOwner)
         public
         onlyWallet
@@ -222,20 +224,44 @@ contract MultiSigWallet {
     /// @param transactionId Transaction ID.
     function executeTransaction(uint transactionId)
         public
+        ownerExists(msg.sender)
+        confirmed(transactionId, msg.sender)
         notExecuted(transactionId)
     {
         if (isConfirmed(transactionId)) {
-            Transaction tx = transactions[transactionId];
-            tx.executed = true;
-            if (tx.destination.call.value(tx.value)(tx.data))
+            Transaction storage txn = transactions[transactionId];
+            txn.executed = true;
+            if (external_call(txn.destination, txn.value, txn.data.length, txn.data))
                 Execution(transactionId);
             else {
                 ExecutionFailure(transactionId);
-                tx.executed = false;
+                txn.executed = false;
             }
         }
     }
 
+    // call has been separated into its own function in order to take advantage
+    // of the Solidity's code generator to produce a loop that copies tx.data into memory.
+    function external_call(address destination, uint value, uint dataLength, bytes data) internal returns (bool) {
+        bool result;
+        assembly {
+            let x := mload(0x40)   // "Allocate" memory for output (0x40 is where "free memory" pointer is stored by convention)
+            let d := add(data, 32) // First 32 bytes are the padded length of data, so exclude that
+            result := call(
+                sub(gas, 34710),   // 34710 is the value that solidity is currently emitting
+                                   // It includes callGas (700) + callVeryLow (3, to pay for SUB) + callValueTransferGas (9000) +
+                                   // callNewAccountGas (25000, in case the destination address does not exist and needs creating)
+                destination,
+                value,
+                d,
+                dataLength,        // Size of the input (in bytes) - this is what fixes the padding problem
+                x,
+                0                  // Output is ignored, therefore the output size is zero
+            )
+        }
+        return result;
+    }
+
     /// @dev Returns the confirmation status of a transaction.
     /// @param transactionId Transaction ID.
     /// @return Confirmation status.
@@ -364,4 +390,4 @@ contract MultiSigWallet {
         for (i=from; i<to; i++)
             _transactionIds[i - from] = transactionIdsTemp[i];
     }
-}
+}
\ No newline at end of file
diff --git a/packages/contracts/src/2.0.0/multisig/MultiSigWalletWithTimeLock.sol b/packages/contracts/src/2.0.0/multisig/MultiSigWalletWithTimeLock.sol
index 8c5e6e1e6..9513d3b30 100644
--- a/packages/contracts/src/2.0.0/multisig/MultiSigWalletWithTimeLock.sol
+++ b/packages/contracts/src/2.0.0/multisig/MultiSigWalletWithTimeLock.sol
@@ -16,47 +16,57 @@
 
 */
 
-// solhint-disable
-pragma solidity ^0.4.10;
+pragma solidity 0.4.24;
 
 import "./MultiSigWallet.sol";
 
 
 /// @title Multisignature wallet with time lock- Allows multiple parties to execute a transaction after a time lock has passed.
 /// @author Amir Bandeali - <amir@0xProject.com>
-contract MultiSigWalletWithTimeLock is MultiSigWallet {
-
-    event ConfirmationTimeSet(uint indexed transactionId, uint confirmationTime);
-    event TimeLockChange(uint secondsTimeLocked);
-
-    uint public secondsTimeLocked;
-
-    mapping (uint => uint) public confirmationTimes;
-
-    modifier notFullyConfirmed(uint transactionId) {
-        require(!isConfirmed(transactionId));
+// solhint-disable not-rely-on-time
+contract MultiSigWalletWithTimeLock is
+    MultiSigWallet
+{
+    event ConfirmationTimeSet(uint256 indexed transactionId, uint256 confirmationTime);
+    event TimeLockChange(uint256 secondsTimeLocked);
+
+    uint256 public secondsTimeLocked;
+
+    mapping (uint256 => uint256) public confirmationTimes;
+
+    modifier notFullyConfirmed(uint256 transactionId) {
+        require(
+            !isConfirmed(transactionId),
+            "TX_FULLY_CONFIRMED"
+        );
         _;
     }
 
-    modifier fullyConfirmed(uint transactionId) {
-        require(isConfirmed(transactionId));
+    modifier fullyConfirmed(uint256 transactionId) {
+        require(
+            isConfirmed(transactionId),
+            "TX_NOT_FULLY_CONFIRMED"
+        );
         _;
     }
 
-    modifier pastTimeLock(uint transactionId) {
-        require(block.timestamp >= confirmationTimes[transactionId] + secondsTimeLocked);
+    modifier pastTimeLock(uint256 transactionId) {
+        require(
+            block.timestamp >= confirmationTimes[transactionId] + secondsTimeLocked,
+            "TIME_LOCK_INCOMPLETE"
+        );
         _;
     }
 
-    /*
-     * Public functions
-     */
-
     /// @dev Contract constructor sets initial owners, required number of confirmations, and time lock.
     /// @param _owners List of initial owners.
     /// @param _required Number of required confirmations.
     /// @param _secondsTimeLocked Duration needed after a transaction is confirmed and before it becomes executable, in seconds.
-    function MultiSigWalletWithTimeLock(address[] _owners, uint _required, uint _secondsTimeLocked)
+    constructor (
+        address[] _owners,
+        uint256 _required,
+        uint256 _secondsTimeLocked
+    )
         public
         MultiSigWallet(_owners, _required)
     {
@@ -65,17 +75,17 @@ contract MultiSigWalletWithTimeLock is MultiSigWallet {
 
     /// @dev Changes the duration of the time lock for transactions.
     /// @param _secondsTimeLocked Duration needed after a transaction is confirmed and before it becomes executable, in seconds.
-    function changeTimeLock(uint _secondsTimeLocked)
+    function changeTimeLock(uint256 _secondsTimeLocked)
         public
         onlyWallet
     {
         secondsTimeLocked = _secondsTimeLocked;
-        TimeLockChange(_secondsTimeLocked);
+        emit TimeLockChange(_secondsTimeLocked);
     }
 
     /// @dev Allows an owner to confirm a transaction.
     /// @param transactionId Transaction ID.
-    function confirmTransaction(uint transactionId)
+    function confirmTransaction(uint256 transactionId)
         public
         ownerExists(msg.sender)
         transactionExists(transactionId)
@@ -83,52 +93,35 @@ contract MultiSigWalletWithTimeLock is MultiSigWallet {
         notFullyConfirmed(transactionId)
     {
         confirmations[transactionId][msg.sender] = true;
-        Confirmation(msg.sender, transactionId);
+        emit Confirmation(msg.sender, transactionId);
         if (isConfirmed(transactionId)) {
             setConfirmationTime(transactionId, block.timestamp);
         }
     }
 
-    /// @dev Allows an owner to revoke a confirmation for a transaction.
-    /// @param transactionId Transaction ID.
-    function revokeConfirmation(uint transactionId)
-        public
-        ownerExists(msg.sender)
-        confirmed(transactionId, msg.sender)
-        notExecuted(transactionId)
-        notFullyConfirmed(transactionId)
-    {
-        confirmations[transactionId][msg.sender] = false;
-        Revocation(msg.sender, transactionId);
-    }
-
     /// @dev Allows anyone to execute a confirmed transaction.
     /// @param transactionId Transaction ID.
-    function executeTransaction(uint transactionId)
+    function executeTransaction(uint256 transactionId)
         public
         notExecuted(transactionId)
         fullyConfirmed(transactionId)
         pastTimeLock(transactionId)
     {
-        Transaction storage tx = transactions[transactionId];
-        tx.executed = true;
-        if (tx.destination.call.value(tx.value)(tx.data))
-            Execution(transactionId);
-        else {
-            ExecutionFailure(transactionId);
-            tx.executed = false;
+        Transaction storage txn = transactions[transactionId];
+        txn.executed = true;
+        if (external_call(txn.destination, txn.value, txn.data.length, txn.data)) {
+            emit Execution(transactionId);
+        } else {
+            emit ExecutionFailure(transactionId);
+            txn.executed = false;
         }
     }
 
-    /*
-     * Internal functions
-     */
-
     /// @dev Sets the time of when a submission first passed.
-    function setConfirmationTime(uint transactionId, uint confirmationTime)
+    function setConfirmationTime(uint256 transactionId, uint256 confirmationTime)
         internal
     {
         confirmationTimes[transactionId] = confirmationTime;
-        ConfirmationTimeSet(transactionId, confirmationTime);
+        emit ConfirmationTimeSet(transactionId, confirmationTime);
     }
 }
diff --git a/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC20Proxy.sol b/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC20Proxy.sol
index b5cec6b64..258443bca 100644
--- a/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC20Proxy.sol
+++ b/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC20Proxy.sol
@@ -18,7 +18,6 @@
 
 pragma solidity 0.4.24;
 
-import "../../utils/LibBytes/LibBytes.sol";
 import "./MixinAuthorizable.sol";
 
 
@@ -59,15 +58,64 @@ contract ERC20Proxy is
                     mstore(96, 0)
                     revert(0, 100)
                 }
-                
-                /////// Token contract address ///////
-                // The token address is found as follows:
-                // * It is stored at offset 4 in `assetData` contents.
-                // * This is stored at offset 32 from `assetData`.
-                // * The offset to `assetData` from Params is stored at offset
-                //   4 in calldata.
-                // * The offset of Params in calldata is 4.
-                // So we read location 4 and add 32 + 4 + 4 to it.
+
+                // `transferFrom`.
+                // The function is marked `external`, so no abi decodeding is done for
+                // us. Instead, we expect the `calldata` memory to contain the
+                // following:
+                //
+                // | Area     | Offset | Length  | Contents                            |
+                // |----------|--------|---------|-------------------------------------|
+                // | Header   | 0      | 4       | function selector                   |
+                // | Params   |        | 4 * 32  | function parameters:                |
+                // |          | 4      |         |   1. offset to assetData (*)        |
+                // |          | 36     |         |   2. from                           |
+                // |          | 68     |         |   3. to                             |
+                // |          | 100    |         |   4. amount                         |
+                // | Data     |        |         | assetData:                          |
+                // |          | 132    | 32      | assetData Length                    |
+                // |          | 164    | **      | assetData Contents                  |
+                //
+                // (*): offset is computed from start of function parameters, so offset
+                //      by an additional 4 bytes in the calldata.
+                //
+                // (**): see table below to compute length of assetData Contents
+                //
+                // WARNING: The ABIv2 specification allows additional padding between
+                //          the Params and Data section. This will result in a larger
+                //          offset to assetData.
+
+                // Asset data itself is encoded as follows:
+                //
+                // | Area     | Offset | Length  | Contents                            |
+                // |----------|--------|---------|-------------------------------------|
+                // | Header   | 0      | 4       | function selector                   |
+                // | Params   |        | 1 * 32  | function parameters:                |
+                // |          | 4      | 12 + 20 |   1. token address                  |
+
+                // We construct calldata for the `token.transferFrom` ABI.
+                // The layout of this calldata is in the table below.
+                //
+                // | Area     | Offset | Length  | Contents                            |
+                // |----------|--------|---------|-------------------------------------|
+                // | Header   | 0      | 4       | function selector                   |
+                // | Params   |        | 3 * 32  | function parameters:                |
+                // |          | 4      |         |   1. from                           |
+                // |          | 36     |         |   2. to                             |
+                // |          | 68     |         |   3. amount                         |
+
+                /////// Read token address from calldata ///////
+                // * The token address is stored in `assetData`.
+                //
+                // * The "offset to assetData" is stored at offset 4 in the calldata (table 1).
+                //   [assetDataOffsetFromParams = calldataload(4)]
+                //
+                // * Notes that the "offset to assetData" is relative to the "Params" area of calldata;
+                //   add 4 bytes to account for the length of the "Header" area (table 1).
+                //   [assetDataOffsetFromHeader = assetDataOffsetFromParams + 4]
+                //
+                // * The "token address" is offset 32+4=36 bytes into "assetData" (tables 1 & 2).
+                //   [tokenOffset = assetDataOffsetFromHeader + 36 = calldataload(4) + 4 + 36]
                 let token := calldataload(add(calldataload(4), 40))
                 
                 /////// Setup Header Area ///////
@@ -118,6 +166,9 @@ contract ERC20Proxy is
                 mstore(96, 0)
                 revert(0, 100)
             }
+
+            // Revert if undefined function is called
+            revert(0, 0)
         }
     }
 
diff --git a/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC721Proxy.sol b/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC721Proxy.sol
index 6a70c9f60..65b664b8b 100644
--- a/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC721Proxy.sol
+++ b/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC721Proxy.sol
@@ -18,7 +18,6 @@
 
 pragma solidity 0.4.24;
 
-import "../../utils/LibBytes/LibBytes.sol";
 import "./MixinAuthorizable.sol";
 
 
@@ -80,6 +79,8 @@ contract ERC721Proxy is
                 // (*): offset is computed from start of function parameters, so offset
                 //      by an additional 4 bytes in the calldata.
                 //
+                // (**): see table below to compute length of assetData Contents
+                //
                 // WARNING: The ABIv2 specification allows additional padding between
                 //          the Params and Data section. This will result in a larger
                 //          offset to assetData.
@@ -152,6 +153,9 @@ contract ERC721Proxy is
                 mstore(96, 0)
                 revert(0, 100)
             }
+
+            // Revert if undefined function is called
+            revert(0, 0)
         }
     }
 
diff --git a/packages/contracts/src/2.0.0/protocol/AssetProxy/MixinAuthorizable.sol b/packages/contracts/src/2.0.0/protocol/AssetProxy/MixinAuthorizable.sol
index ff4660a31..fe9bbf848 100644
--- a/packages/contracts/src/2.0.0/protocol/AssetProxy/MixinAuthorizable.sol
+++ b/packages/contracts/src/2.0.0/protocol/AssetProxy/MixinAuthorizable.sol
@@ -26,7 +26,6 @@ contract MixinAuthorizable is
     Ownable,
     MAuthorizable
 {
-
     /// @dev Only authorized addresses can invoke functions with this modifier.
     modifier onlyAuthorized {
         require(
diff --git a/packages/contracts/src/2.0.0/protocol/AssetProxy/interfaces/IAssetProxy.sol b/packages/contracts/src/2.0.0/protocol/AssetProxy/interfaces/IAssetProxy.sol
index 3651dd694..b25d2d75a 100644
--- a/packages/contracts/src/2.0.0/protocol/AssetProxy/interfaces/IAssetProxy.sol
+++ b/packages/contracts/src/2.0.0/protocol/AssetProxy/interfaces/IAssetProxy.sol
@@ -24,7 +24,6 @@ import "./IAuthorizable.sol";
 contract IAssetProxy is
     IAuthorizable
 {
-
     /// @dev Transfers assets. Either succeeds or throws.
     /// @param assetData Byte array encoded for the respective asset proxy.
     /// @param from Address to transfer asset from.
diff --git a/packages/contracts/src/2.0.0/protocol/AssetProxy/interfaces/IAuthorizable.sol b/packages/contracts/src/2.0.0/protocol/AssetProxy/interfaces/IAuthorizable.sol
index 8fac43a47..ba1d4aa77 100644
--- a/packages/contracts/src/2.0.0/protocol/AssetProxy/interfaces/IAuthorizable.sol
+++ b/packages/contracts/src/2.0.0/protocol/AssetProxy/interfaces/IAuthorizable.sol
@@ -24,7 +24,6 @@ import "../../../utils/Ownable/IOwnable.sol";
 contract IAuthorizable is
     IOwnable
 {
-
     /// @dev Authorizes an address.
     /// @param target Address to authorize.
     function addAuthorizedAddress(address target)
diff --git a/packages/contracts/src/2.0.0/protocol/AssetProxy/mixins/MAuthorizable.sol b/packages/contracts/src/2.0.0/protocol/AssetProxy/mixins/MAuthorizable.sol
index 8afc8c8d8..d63fb7f6d 100644
--- a/packages/contracts/src/2.0.0/protocol/AssetProxy/mixins/MAuthorizable.sol
+++ b/packages/contracts/src/2.0.0/protocol/AssetProxy/mixins/MAuthorizable.sol
@@ -24,7 +24,6 @@ import "../interfaces/IAuthorizable.sol";
 contract MAuthorizable is
     IAuthorizable
 {
-
     // Event logged when a new address is authorized.
     event AuthorizedAddressAdded(
         address indexed target,
diff --git a/packages/contracts/src/2.0.0/protocol/AssetProxyOwner/AssetProxyOwner.sol b/packages/contracts/src/2.0.0/protocol/AssetProxyOwner/AssetProxyOwner.sol
index 8b7333646..edb788fab 100644
--- a/packages/contracts/src/2.0.0/protocol/AssetProxyOwner/AssetProxyOwner.sol
+++ b/packages/contracts/src/2.0.0/protocol/AssetProxyOwner/AssetProxyOwner.sol
@@ -16,14 +16,16 @@
 
 */
 
-pragma solidity 0.4.10;
+pragma solidity 0.4.24;
 
 import "../../multisig/MultiSigWalletWithTimeLock.sol";
+import "../../utils/LibBytes/LibBytes.sol";
 
 
 contract AssetProxyOwner is
     MultiSigWalletWithTimeLock
 {
+    using LibBytes for bytes;
 
     event AssetProxyRegistration(address assetProxyContract, bool isRegistered);
 
@@ -36,9 +38,15 @@ contract AssetProxyOwner is
     /// @dev Function will revert if the transaction does not call `removeAuthorizedAddressAtIndex`
     ///      on an approved AssetProxy contract.
     modifier validRemoveAuthorizedAddressAtIndexTx(uint256 transactionId) {
-        Transaction storage tx = transactions[transactionId];
-        require(isAssetProxyRegistered[tx.destination]);
-        require(readBytes4(tx.data, 0) == REMOVE_AUTHORIZED_ADDRESS_AT_INDEX_SELECTOR);
+        Transaction storage txn = transactions[transactionId];
+        require(
+            isAssetProxyRegistered[txn.destination],
+            "UNREGISTERED_ASSET_PROXY"
+        );
+        require(
+            txn.data.readBytes4(0) == REMOVE_AUTHORIZED_ADDRESS_AT_INDEX_SELECTOR,
+            "INVALID_FUNCTION_SELECTOR"
+        );
         _;
     }
 
@@ -48,7 +56,7 @@ contract AssetProxyOwner is
     /// @param _assetProxyContracts Array of AssetProxy contract addresses.
     /// @param _required Number of required confirmations.
     /// @param _secondsTimeLocked Duration needed after a transaction is confirmed and before it becomes executable, in seconds.
-    function AssetProxyOwner(
+    constructor (
         address[] memory _owners,
         address[] memory _assetProxyContracts,
         uint256 _required,
@@ -59,7 +67,10 @@ contract AssetProxyOwner is
     {
         for (uint256 i = 0; i < _assetProxyContracts.length; i++) {
             address assetProxy = _assetProxyContracts[i];
-            require(assetProxy != address(0));
+            require(
+                assetProxy != address(0),
+                "INVALID_ASSET_PROXY"
+            );
             isAssetProxyRegistered[assetProxy] = true;
         }
     }
@@ -74,7 +85,7 @@ contract AssetProxyOwner is
         notNull(assetProxyContract)
     {
         isAssetProxyRegistered[assetProxyContract] = isRegistered;
-        AssetProxyRegistration(assetProxyContract, isRegistered);
+        emit AssetProxyRegistration(assetProxyContract, isRegistered);
     }
 
     /// @dev Allows execution of `removeAuthorizedAddressAtIndex` without time lock.
@@ -85,35 +96,13 @@ contract AssetProxyOwner is
         fullyConfirmed(transactionId)
         validRemoveAuthorizedAddressAtIndexTx(transactionId)
     {
-        Transaction storage tx = transactions[transactionId];
-        tx.executed = true;
-        // solhint-disable-next-line avoid-call-value
-        if (tx.destination.call.value(tx.value)(tx.data))
-            Execution(transactionId);
-        else {
-            ExecutionFailure(transactionId);
-            tx.executed = false;
+        Transaction storage txn = transactions[transactionId];
+        txn.executed = true;
+        if (external_call(txn.destination, txn.value, txn.data.length, txn.data)) {
+            emit Execution(transactionId);
+        } else {
+            emit ExecutionFailure(transactionId);
+            txn.executed = false;
         }
     }
-
-    /// @dev Reads an unpadded bytes4 value from a position in a byte array.
-    /// @param b Byte array containing a bytes4 value.
-    /// @param index Index in byte array of bytes4 value.
-    /// @return bytes4 value from byte array.
-    function readBytes4(
-        bytes memory b,
-        uint256 index
-    )
-        internal
-        returns (bytes4 result)
-    {
-        require(b.length >= index + 4);
-        assembly {
-            result := mload(add(b, 32))
-            // Solidity does not require us to clean the trailing bytes.
-            // We do it anyway
-            result := and(result, 0xFFFFFFFF00000000000000000000000000000000000000000000000000000000)
-        }
-        return result;
-    }
 }
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/Exchange.sol b/packages/contracts/src/2.0.0/protocol/Exchange/Exchange.sol
index 7507d3da1..ead36009f 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/Exchange.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/Exchange.sol
@@ -37,7 +37,6 @@ contract Exchange is
     MixinAssetProxyDispatcher,
     MixinWrapperFunctions
 {
-
     string constant public VERSION = "2.0.1-alpha";
 
     // Mixins are instantiated in the order they are inherited
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/MixinAssetProxyDispatcher.sol b/packages/contracts/src/2.0.0/protocol/Exchange/MixinAssetProxyDispatcher.sol
index e9f882194..87b09b6b3 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/MixinAssetProxyDispatcher.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/MixinAssetProxyDispatcher.sol
@@ -19,7 +19,6 @@
 pragma solidity 0.4.24;
 
 import "../../utils/Ownable/Ownable.sol";
-import "../../utils/LibBytes/LibBytes.sol";
 import "./mixins/MAssetProxyDispatcher.sol";
 import "../AssetProxy/interfaces/IAssetProxy.sol";
 
@@ -28,8 +27,6 @@ contract MixinAssetProxyDispatcher is
     Ownable,
     MAssetProxyDispatcher
 {
-    using LibBytes for bytes;
-    
     // Mapping from Asset Proxy Id's to their respective Asset Proxy
     mapping (bytes4 => IAssetProxy) public assetProxies;
 
@@ -83,14 +80,14 @@ contract MixinAssetProxyDispatcher is
         internal
     {
         // Do nothing if no amount should be transferred.
-        if (amount > 0) {
+        if (amount > 0 && from != to) {
             // Ensure assetData length is valid
             require(
                 assetData.length > 3,
                 "LENGTH_GREATER_THAN_3_REQUIRED"
             );
             
-            // Lookup assetProxy
+            // Lookup assetProxy. We do not use `LibBytes.readBytes4` for gas efficiency reasons.
             bytes4 assetProxyId;
             assembly {
                 assetProxyId := and(mload(
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/MixinExchangeCore.sol b/packages/contracts/src/2.0.0/protocol/Exchange/MixinExchangeCore.sol
index ab5c6e507..736dcd0b1 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/MixinExchangeCore.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/MixinExchangeCore.sol
@@ -19,6 +19,7 @@
 pragma solidity 0.4.24;
 pragma experimental ABIEncoderV2;
 
+import "../../utils/ReentrancyGuard/ReentrancyGuard.sol";
 import "./libs/LibConstants.sol";
 import "./libs/LibFillResults.sol";
 import "./libs/LibOrder.sol";
@@ -30,6 +31,7 @@ import "./mixins/MAssetProxyDispatcher.sol";
 
 
 contract MixinExchangeCore is
+    ReentrancyGuard,
     LibConstants,
     LibMath,
     LibOrder,
@@ -54,6 +56,7 @@ contract MixinExchangeCore is
     /// @param targetOrderEpoch Orders created with a salt less or equal to this value will be cancelled.
     function cancelOrdersUpTo(uint256 targetOrderEpoch)
         external
+        nonReentrant
     {
         address makerAddress = getCurrentContextAddress();
         // If this function is called via `executeTransaction`, we only update the orderEpoch for the makerAddress/msg.sender combination.
@@ -72,7 +75,11 @@ contract MixinExchangeCore is
 
         // Update orderEpoch
         orderEpoch[makerAddress][senderAddress] = newOrderEpoch;
-        emit CancelUpTo(makerAddress, senderAddress, newOrderEpoch);
+        emit CancelUpTo(
+            makerAddress,
+            senderAddress,
+            newOrderEpoch
+        );
     }
 
     /// @dev Fills the input order.
@@ -86,43 +93,14 @@ contract MixinExchangeCore is
         bytes memory signature
     )
         public
+        nonReentrant
         returns (FillResults memory fillResults)
     {
-        // Fetch order info
-        OrderInfo memory orderInfo = getOrderInfo(order);
-
-        // Fetch taker address
-        address takerAddress = getCurrentContextAddress();
-
-        // Get amount of takerAsset to fill
-        uint256 remainingTakerAssetAmount = safeSub(order.takerAssetAmount, orderInfo.orderTakerAssetFilledAmount);
-        uint256 takerAssetFilledAmount = min256(takerAssetFillAmount, remainingTakerAssetAmount);
-
-        // Validate context
-        assertValidFill(
+        fillResults = fillOrderInternal(
             order,
-            orderInfo,
-            takerAddress,
             takerAssetFillAmount,
-            takerAssetFilledAmount,
             signature
         );
-
-        // Compute proportional fill amounts
-        fillResults = calculateFillResults(order, takerAssetFilledAmount);
-
-        // Update exchange internal state
-        updateFilledState(
-            order,
-            takerAddress,
-            orderInfo.orderHash,
-            orderInfo.orderTakerAssetFilledAmount,
-            fillResults
-        );
-    
-        // Settle order
-        settleOrder(order, takerAddress, fillResults);
-
         return fillResults;
     }
 
@@ -131,15 +109,9 @@ contract MixinExchangeCore is
     /// @param order Order to cancel. Order must be OrderStatus.FILLABLE.
     function cancelOrder(Order memory order)
         public
+        nonReentrant
     {
-        // Fetch current order status
-        OrderInfo memory orderInfo = getOrderInfo(order);
-
-        // Validate context
-        assertValidCancel(order, orderInfo);
-
-        // Perform cancel
-        updateCancelledState(order, orderInfo.orderHash);
+        cancelOrderInternal(order);
     }
 
     /// @dev Gets information about an order: status, hash, and amount filled.
@@ -203,6 +175,84 @@ contract MixinExchangeCore is
         return orderInfo;
     }
 
+    /// @dev Fills the input order.
+    /// @param order Order struct containing order specifications.
+    /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
+    /// @param signature Proof that order has been created by maker.
+    /// @return Amounts filled and fees paid by maker and taker.
+    function fillOrderInternal(
+        Order memory order,
+        uint256 takerAssetFillAmount,
+        bytes memory signature
+    )
+        internal
+        returns (FillResults memory fillResults)
+    {
+        // Fetch order info
+        OrderInfo memory orderInfo = getOrderInfo(order);
+
+        // Fetch taker address
+        address takerAddress = getCurrentContextAddress();
+        
+        // Assert that the order is fillable by taker
+        assertFillableOrder(
+            order,
+            orderInfo,
+            takerAddress,
+            signature
+        );
+        
+        // Get amount of takerAsset to fill
+        uint256 remainingTakerAssetAmount = safeSub(order.takerAssetAmount, orderInfo.orderTakerAssetFilledAmount);
+        uint256 takerAssetFilledAmount = min256(takerAssetFillAmount, remainingTakerAssetAmount);
+
+        // Validate context
+        assertValidFill(
+            order,
+            orderInfo,
+            takerAssetFillAmount,
+            takerAssetFilledAmount,
+            fillResults.makerAssetFilledAmount
+        );
+
+        // Compute proportional fill amounts
+        fillResults = calculateFillResults(order, takerAssetFilledAmount);
+
+        // Update exchange internal state
+        updateFilledState(
+            order,
+            takerAddress,
+            orderInfo.orderHash,
+            orderInfo.orderTakerAssetFilledAmount,
+            fillResults
+        );
+    
+        // Settle order
+        settleOrder(
+            order,
+            takerAddress,
+            fillResults
+        );
+
+        return fillResults;
+    }
+
+    /// @dev After calling, the order can not be filled anymore.
+    ///      Throws if order is invalid or sender does not have permission to cancel.
+    /// @param order Order to cancel. Order must be OrderStatus.FILLABLE.
+    function cancelOrderInternal(Order memory order)
+        internal
+    {
+        // Fetch current order status
+        OrderInfo memory orderInfo = getOrderInfo(order);
+
+        // Validate context
+        assertValidCancel(order, orderInfo);
+
+        // Perform cancel
+        updateCancelledState(order, orderInfo.orderHash);
+    }
+
     /// @dev Updates state with results of a fill order.
     /// @param order that was filled.
     /// @param takerAddress Address of taker who filled the order.
@@ -259,20 +309,16 @@ contract MixinExchangeCore is
             order.takerAssetData
         );
     }
-
+    
     /// @dev Validates context for fillOrder. Succeeds or throws.
     /// @param order to be filled.
     /// @param orderInfo OrderStatus, orderHash, and amount already filled of order.
     /// @param takerAddress Address of order taker.
-    /// @param takerAssetFillAmount Desired amount of order to fill by taker.
-    /// @param takerAssetFilledAmount Amount of takerAsset that will be filled.
     /// @param signature Proof that the orders was created by its maker.
-    function assertValidFill(
+    function assertFillableOrder(
         Order memory order,
         OrderInfo memory orderInfo,
         address takerAddress,
-        uint256 takerAssetFillAmount,
-        uint256 takerAssetFilledAmount,
         bytes memory signature
     )
         internal
@@ -283,13 +329,7 @@ contract MixinExchangeCore is
             orderInfo.orderStatus == uint8(OrderStatus.FILLABLE),
             "ORDER_UNFILLABLE"
         );
-
-        // Revert if fill amount is invalid
-        require(
-            takerAssetFillAmount != 0,
-            "INVALID_TAKER_AMOUNT"
-        );
-
+        
         // Validate sender is allowed to fill this order
         if (order.senderAddress != address(0)) {
             require(
@@ -297,7 +337,7 @@ contract MixinExchangeCore is
                 "INVALID_SENDER"
             );
         }
-
+        
         // Validate taker is allowed to fill this order
         if (order.takerAddress != address(0)) {
             require(
@@ -305,7 +345,7 @@ contract MixinExchangeCore is
                 "INVALID_TAKER"
             );
         }
-
+        
         // Validate Maker signature (check only if first time seen)
         if (orderInfo.orderTakerAssetFilledAmount == 0) {
             require(
@@ -317,15 +357,69 @@ contract MixinExchangeCore is
                 "INVALID_ORDER_SIGNATURE"
             );
         }
-
-        // Validate fill order rounding
+    }
+    
+    /// @dev Validates context for fillOrder. Succeeds or throws.
+    /// @param order to be filled.
+    /// @param orderInfo OrderStatus, orderHash, and amount already filled of order.
+    /// @param takerAssetFillAmount Desired amount of order to fill by taker.
+    /// @param takerAssetFilledAmount Amount of takerAsset that will be filled.
+    /// @param makerAssetFilledAmount Amount of makerAsset that will be transfered.
+    function assertValidFill(
+        Order memory order,
+        OrderInfo memory orderInfo,
+        uint256 takerAssetFillAmount,  // TODO: use FillResults
+        uint256 takerAssetFilledAmount,
+        uint256 makerAssetFilledAmount
+    )
+        internal
+        view
+    {
+        // Revert if fill amount is invalid
+        // TODO: reconsider necessity for v2.1
         require(
-            !isRoundingError(
-                takerAssetFilledAmount,
-                order.takerAssetAmount,
-                order.makerAssetAmount
-            ),
-            "ROUNDING_ERROR"
+            takerAssetFillAmount != 0,
+            "INVALID_TAKER_AMOUNT"
+        );
+        
+        // Make sure taker does not pay more than desired amount
+        // NOTE: This assertion should never fail, it is here
+        //       as an extra defence against potential bugs.
+        require(
+            takerAssetFilledAmount <= takerAssetFillAmount,
+            "TAKER_OVERPAY"
+        );
+        
+        // Make sure order is not overfilled
+        // NOTE: This assertion should never fail, it is here
+        //       as an extra defence against potential bugs.
+        require(
+            safeAdd(orderInfo.orderTakerAssetFilledAmount, takerAssetFilledAmount) <= order.takerAssetAmount,
+            "ORDER_OVERFILL"
+        );
+        
+        // Make sure order is filled at acceptable price.
+        // The order has an implied price from the makers perspective:
+        //    order price = order.makerAssetAmount / order.takerAssetAmount
+        // i.e. the number of makerAsset maker is paying per takerAsset. The
+        // maker is guaranteed to get this price or a better (lower) one. The
+        // actual price maker is getting in this fill is:
+        //    fill price = makerAssetFilledAmount / takerAssetFilledAmount
+        // We need `fill price <= order price` for the fill to be fair to maker.
+        // This amounts to:
+        //     makerAssetFilledAmount        order.makerAssetAmount
+        //    ------------------------  <=  -----------------------
+        //     takerAssetFilledAmount        order.takerAssetAmount
+        // or, equivalently:
+        //     makerAssetFilledAmount * order.takerAssetAmount <=
+        //     order.makerAssetAmount * takerAssetFilledAmount
+        // NOTE: This assertion should never fail, it is here
+        //       as an extra defence against potential bugs.
+        require(
+            safeMul(makerAssetFilledAmount, order.takerAssetAmount)
+            <= 
+            safeMul(order.makerAssetAmount, takerAssetFilledAmount),
+            "INVALID_FILL_PRICE"
         );
     }
 
@@ -376,17 +470,17 @@ contract MixinExchangeCore is
     {
         // Compute proportional transfer amounts
         fillResults.takerAssetFilledAmount = takerAssetFilledAmount;
-        fillResults.makerAssetFilledAmount = getPartialAmount(
+        fillResults.makerAssetFilledAmount = safeGetPartialAmountFloor(
             takerAssetFilledAmount,
             order.takerAssetAmount,
             order.makerAssetAmount
         );
-        fillResults.makerFeePaid = getPartialAmount(
-            takerAssetFilledAmount,
-            order.takerAssetAmount,
+        fillResults.makerFeePaid = safeGetPartialAmountFloor(
+            fillResults.makerAssetFilledAmount,
+            order.makerAssetAmount,
             order.makerFee
         );
-        fillResults.takerFeePaid = getPartialAmount(
+        fillResults.takerFeePaid = safeGetPartialAmountFloor(
             takerAssetFilledAmount,
             order.takerAssetAmount,
             order.takerFee
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/MixinMatchOrders.sol b/packages/contracts/src/2.0.0/protocol/Exchange/MixinMatchOrders.sol
index 56b309a1b..b4f6bdb26 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/MixinMatchOrders.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/MixinMatchOrders.sol
@@ -14,6 +14,7 @@
 pragma solidity 0.4.24;
 pragma experimental ABIEncoderV2;
 
+import "../../utils/ReentrancyGuard/ReentrancyGuard.sol";
 import "./libs/LibConstants.sol";
 import "./libs/LibMath.sol";
 import "./libs/LibOrder.sol";
@@ -25,6 +26,7 @@ import "./mixins/MAssetProxyDispatcher.sol";
 
 
 contract MixinMatchOrders is
+    ReentrancyGuard,
     LibConstants,
     LibMath,
     MAssetProxyDispatcher,
@@ -48,6 +50,7 @@ contract MixinMatchOrders is
         bytes memory rightSignature
     )
         public
+        nonReentrant
         returns (LibFillResults.MatchedFillResults memory matchedFillResults)
     {
         // We assume that rightOrder.takerAssetData == leftOrder.makerAssetData and rightOrder.makerAssetData == leftOrder.takerAssetData.
@@ -61,8 +64,20 @@ contract MixinMatchOrders is
 
         // Fetch taker address
         address takerAddress = getCurrentContextAddress();
-
+        
         // Either our context is valid or we revert
+        assertFillableOrder(
+            leftOrder,
+            leftOrderInfo,
+            takerAddress,
+            leftSignature
+        );
+        assertFillableOrder(
+            rightOrder,
+            rightOrderInfo,
+            takerAddress,
+            rightSignature
+        );
         assertValidMatch(leftOrder, rightOrder);
 
         // Compute proportional fill amounts
@@ -77,20 +92,18 @@ contract MixinMatchOrders is
         assertValidFill(
             leftOrder,
             leftOrderInfo,
-            takerAddress,
             matchedFillResults.left.takerAssetFilledAmount,
             matchedFillResults.left.takerAssetFilledAmount,
-            leftSignature
+            matchedFillResults.left.makerAssetFilledAmount
         );
         assertValidFill(
             rightOrder,
             rightOrderInfo,
-            takerAddress,
             matchedFillResults.right.takerAssetFilledAmount,
             matchedFillResults.right.takerAssetFilledAmount,
-            rightSignature
+            matchedFillResults.right.makerAssetFilledAmount
         );
-
+        
         // Update exchange state
         updateFilledState(
             leftOrder,
@@ -106,7 +119,7 @@ contract MixinMatchOrders is
             rightOrderInfo.orderTakerAssetFilledAmount,
             matchedFillResults.right
         );
-    
+
         // Settle matched orders. Succeeds or throws.
         settleMatchedOrders(
             leftOrder,
@@ -162,62 +175,85 @@ contract MixinMatchOrders is
         pure
         returns (LibFillResults.MatchedFillResults memory matchedFillResults)
     {
-        // We settle orders at the exchange rate of the right order.
-        // The amount saved by the left maker goes to the taker.
-        // Either the left or right order will be fully filled; possibly both.
-        // The left order is fully filled iff the right order can sell more than left can buy.
-        // That is: the amount required to fill the left order is less than or equal to
-        //          the amount we can spend from the right order:
-        //          <leftTakerAssetAmountRemaining> <= <rightTakerAssetAmountRemaining> * <rightMakerToTakerRatio>
-        //          <leftTakerAssetAmountRemaining> <= <rightTakerAssetAmountRemaining> * <rightOrder.makerAssetAmount> / <rightOrder.takerAssetAmount>
-        //          <leftTakerAssetAmountRemaining> * <rightOrder.takerAssetAmount> <= <rightTakerAssetAmountRemaining> * <rightOrder.makerAssetAmount>
+        // Derive maker asset amounts for left & right orders, given store taker assert amounts
         uint256 leftTakerAssetAmountRemaining = safeSub(leftOrder.takerAssetAmount, leftOrderTakerAssetFilledAmount);
+        uint256 leftMakerAssetAmountRemaining = safeGetPartialAmountFloor(
+            leftOrder.makerAssetAmount,
+            leftOrder.takerAssetAmount,
+            leftTakerAssetAmountRemaining
+        );
         uint256 rightTakerAssetAmountRemaining = safeSub(rightOrder.takerAssetAmount, rightOrderTakerAssetFilledAmount);
-        uint256 leftTakerAssetFilledAmount;
-        uint256 rightTakerAssetFilledAmount;
-        if (
-            safeMul(leftTakerAssetAmountRemaining, rightOrder.takerAssetAmount) <=
-            safeMul(rightTakerAssetAmountRemaining, rightOrder.makerAssetAmount)
-        ) {
-            // Left order will be fully filled: maximally fill left
-            leftTakerAssetFilledAmount = leftTakerAssetAmountRemaining;
+        uint256 rightMakerAssetAmountRemaining = safeGetPartialAmountFloor(
+            rightOrder.makerAssetAmount,
+            rightOrder.takerAssetAmount,
+            rightTakerAssetAmountRemaining
+        );
 
-            // The right order receives an amount proportional to how much was spent.
-            rightTakerAssetFilledAmount = getPartialAmount(
-                rightOrder.takerAssetAmount,
-                rightOrder.makerAssetAmount,
-                leftTakerAssetFilledAmount
+        // Calculate fill results for maker and taker assets: at least one order will be fully filled.
+        // The maximum amount the left maker can buy is `leftTakerAssetAmountRemaining`
+        // The maximum amount the right maker can sell is `rightMakerAssetAmountRemaining`
+        // We have two distinct cases for calculating the fill results:
+        // Case 1.
+        //   If the left maker can buy more than the right maker can sell, then only the right order is fully filled.
+        //   If the left maker can buy exactly what the right maker can sell, then both orders are fully filled.
+        // Case 2.
+        //   If the left maker cannot buy more than the right maker can sell, then only the left order is fully filled.
+        if (leftTakerAssetAmountRemaining >= rightMakerAssetAmountRemaining) {
+            // Case 1: Right order is fully filled
+            matchedFillResults.right.makerAssetFilledAmount = rightMakerAssetAmountRemaining;
+            matchedFillResults.right.takerAssetFilledAmount = rightTakerAssetAmountRemaining;
+            matchedFillResults.left.takerAssetFilledAmount = matchedFillResults.right.makerAssetFilledAmount;
+            // Round down to ensure the maker's exchange rate does not exceed the price specified by the order. 
+            // We favor the maker when the exchange rate must be rounded.
+            matchedFillResults.left.makerAssetFilledAmount = safeGetPartialAmountFloor(
+                leftOrder.makerAssetAmount,
+                leftOrder.takerAssetAmount,
+                matchedFillResults.left.takerAssetFilledAmount
             );
         } else {
-            // Right order will be fully filled: maximally fill right
-            rightTakerAssetFilledAmount = rightTakerAssetAmountRemaining;
-
-            // The left order receives an amount proportional to how much was spent.
-            leftTakerAssetFilledAmount = getPartialAmount(
-                rightOrder.makerAssetAmount,
+            // Case 2: Left order is fully filled
+            matchedFillResults.left.makerAssetFilledAmount = leftMakerAssetAmountRemaining;
+            matchedFillResults.left.takerAssetFilledAmount = leftTakerAssetAmountRemaining;
+            matchedFillResults.right.makerAssetFilledAmount = matchedFillResults.left.takerAssetFilledAmount;
+            // Round up to ensure the maker's exchange rate does not exceed the price specified by the order.
+            // We favor the maker when the exchange rate must be rounded.
+            matchedFillResults.right.takerAssetFilledAmount = safeGetPartialAmountCeil(
                 rightOrder.takerAssetAmount,
-                rightTakerAssetFilledAmount
+                rightOrder.makerAssetAmount,
+                matchedFillResults.right.makerAssetFilledAmount
             );
         }
 
-        // Calculate fill results for left order
-        matchedFillResults.left = calculateFillResults(
-            leftOrder,
-            leftTakerAssetFilledAmount
-        );
-
-        // Calculate fill results for right order
-        matchedFillResults.right = calculateFillResults(
-            rightOrder,
-            rightTakerAssetFilledAmount
-        );
-
         // Calculate amount given to taker
         matchedFillResults.leftMakerAssetSpreadAmount = safeSub(
             matchedFillResults.left.makerAssetFilledAmount,
             matchedFillResults.right.takerAssetFilledAmount
         );
 
+        // Compute fees for left order
+        matchedFillResults.left.makerFeePaid = safeGetPartialAmountFloor(
+            matchedFillResults.left.makerAssetFilledAmount,
+            leftOrder.makerAssetAmount,
+            leftOrder.makerFee
+        );
+        matchedFillResults.left.takerFeePaid = safeGetPartialAmountFloor(
+            matchedFillResults.left.takerAssetFilledAmount,
+            leftOrder.takerAssetAmount,
+            leftOrder.takerFee
+        );
+
+        // Compute fees for right order
+        matchedFillResults.right.makerFeePaid = safeGetPartialAmountFloor(
+            matchedFillResults.right.makerAssetFilledAmount,
+            rightOrder.makerAssetAmount,
+            rightOrder.makerFee
+        );
+        matchedFillResults.right.takerFeePaid = safeGetPartialAmountFloor(
+            matchedFillResults.right.takerAssetFilledAmount,
+            rightOrder.takerAssetAmount,
+            rightOrder.takerFee
+        );
+
         // Return fill results
         return matchedFillResults;
     }
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/MixinSignatureValidator.sol b/packages/contracts/src/2.0.0/protocol/Exchange/MixinSignatureValidator.sol
index 44de54817..176e28351 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/MixinSignatureValidator.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/MixinSignatureValidator.sol
@@ -19,6 +19,7 @@
 pragma solidity 0.4.24;
 
 import "../../utils/LibBytes/LibBytes.sol";
+import "../../utils/ReentrancyGuard/ReentrancyGuard.sol";
 import "./mixins/MSignatureValidator.sol";
 import "./mixins/MTransactions.sol";
 import "./interfaces/IWallet.sol";
@@ -26,6 +27,7 @@ import "./interfaces/IValidator.sol";
 
 
 contract MixinSignatureValidator is
+    ReentrancyGuard,
     MSignatureValidator,
     MTransactions
 {
@@ -48,14 +50,16 @@ contract MixinSignatureValidator is
     )
         external
     {
-        require(
-            isValidSignature(
-                hash,
-                signerAddress,
-                signature
-            ),
-            "INVALID_SIGNATURE"
-        );
+        if (signerAddress != msg.sender) {
+            require(
+                isValidSignature(
+                    hash,
+                    signerAddress,
+                    signature
+                ),
+                "INVALID_SIGNATURE"
+            );
+        }
         preSigned[hash][signerAddress] = true;
     }
 
@@ -67,6 +71,7 @@ contract MixinSignatureValidator is
         bool approval
     )
         external
+        nonReentrant
     {
         address signerAddress = getCurrentContextAddress();
         allowedValidators[signerAddress][validatorAddress] = approval;
@@ -172,26 +177,14 @@ contract MixinSignatureValidator is
             isValid = signerAddress == recovered;
             return isValid;
 
-        // Implicitly signed by caller.
-        // The signer has initiated the call. In the case of non-contract
-        // accounts it means the transaction itself was signed.
-        // Example: let's say for a particular operation three signatures
-        // A, B and C are required. To submit the transaction, A and B can
-        // give a signature to C, who can then submit the transaction using
-        // `Caller` for his own signature. Or A and C can sign and B can
-        // submit using `Caller`. Having `Caller` allows this flexibility.
-        } else if (signatureType == SignatureType.Caller) {
-            require(
-                signature.length == 0,
-                "LENGTH_0_REQUIRED"
-            );
-            isValid = signerAddress == msg.sender;
-            return isValid;
-
         // Signature verified by wallet contract.
         // If used with an order, the maker of the order is the wallet contract.
         } else if (signatureType == SignatureType.Wallet) {
-            isValid = IWallet(signerAddress).isValidSignature(hash, signature);
+            isValid = isValidWalletSignature(
+                hash,
+                signerAddress,
+                signature
+            );
             return isValid;
 
         // Signature verified by validator contract.
@@ -209,7 +202,8 @@ contract MixinSignatureValidator is
             if (!allowedValidators[signerAddress][validatorAddress]) {
                 return false;
             }
-            isValid = IValidator(validatorAddress).isValidSignature(
+            isValid = isValidValidatorSignature(
+                validatorAddress,
                 hash,
                 signerAddress,
                 signature
@@ -220,34 +214,6 @@ contract MixinSignatureValidator is
         } else if (signatureType == SignatureType.PreSigned) {
             isValid = preSigned[hash][signerAddress];
             return isValid;
-
-        // Signature from Trezor hardware wallet.
-        // It differs from web3.eth_sign in the encoding of message length
-        // (Bitcoin varint encoding vs ascii-decimal, the latter is not
-        // self-terminating which leads to ambiguities).
-        // See also:
-        // https://en.bitcoin.it/wiki/Protocol_documentation#Variable_length_integer
-        // https://github.com/trezor/trezor-mcu/blob/master/firmware/ethereum.c#L602
-        // https://github.com/trezor/trezor-mcu/blob/master/firmware/crypto.c#L36
-        } else if (signatureType == SignatureType.Trezor) {
-            require(
-                signature.length == 65,
-                "LENGTH_65_REQUIRED"
-            );
-            v = uint8(signature[0]);
-            r = signature.readBytes32(1);
-            s = signature.readBytes32(33);
-            recovered = ecrecover(
-                keccak256(abi.encodePacked(
-                    "\x19Ethereum Signed Message:\n\x20",
-                    hash
-                )),
-                v,
-                r,
-                s
-            );
-            isValid = signerAddress == recovered;
-            return isValid;
         }
 
         // Anything else is illegal (We do not return false because
@@ -257,4 +223,102 @@ contract MixinSignatureValidator is
         // signature was invalid.)
         revert("SIGNATURE_UNSUPPORTED");
     }
+
+    /// @dev Verifies signature using logic defined by Wallet contract.
+    /// @param hash Any 32 byte hash.
+    /// @param walletAddress Address that should have signed the given hash
+    ///                      and defines its own signature verification method.
+    /// @param signature Proof that the hash has been signed by signer.
+    /// @return True if signature is valid for given wallet..
+    function isValidWalletSignature(
+        bytes32 hash,
+        address walletAddress,
+        bytes signature
+    )
+        internal
+        view
+        returns (bool isValid)
+    {
+        bytes memory calldata = abi.encodeWithSelector(
+            IWallet(walletAddress).isValidSignature.selector,
+            hash,
+            signature
+        );
+        assembly {
+            let cdStart := add(calldata, 32)
+            let success := staticcall(
+                gas,              // forward all gas
+                walletAddress,    // address of Wallet contract
+                cdStart,          // pointer to start of input
+                mload(calldata),  // length of input
+                cdStart,          // write output over input
+                32                // output size is 32 bytes
+            )
+
+            switch success
+            case 0 {
+                // Revert with `Error("WALLET_ERROR")`
+                mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000)
+                mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000)
+                mstore(64, 0x0000000c57414c4c45545f4552524f5200000000000000000000000000000000)
+                mstore(96, 0)
+                revert(0, 100)
+            }
+            case 1 {
+                // Signature is valid if call did not revert and returned true
+                isValid := mload(cdStart)
+            }
+        }
+        return isValid;
+    }
+
+    /// @dev Verifies signature using logic defined by Validator contract.
+    /// @param validatorAddress Address of validator contract.
+    /// @param hash Any 32 byte hash.
+    /// @param signerAddress Address that should have signed the given hash.
+    /// @param signature Proof that the hash has been signed by signer.
+    /// @return True if the address recovered from the provided signature matches the input signer address.
+    function isValidValidatorSignature(
+        address validatorAddress,
+        bytes32 hash,
+        address signerAddress,
+        bytes signature
+    )
+        internal
+        view
+        returns (bool isValid)
+    {
+        bytes memory calldata = abi.encodeWithSelector(
+            IValidator(signerAddress).isValidSignature.selector,
+            hash,
+            signerAddress,
+            signature
+        );
+        assembly {
+            let cdStart := add(calldata, 32)
+            let success := staticcall(
+                gas,               // forward all gas
+                validatorAddress,  // address of Validator contract
+                cdStart,           // pointer to start of input
+                mload(calldata),   // length of input
+                cdStart,           // write output over input
+                32                 // output size is 32 bytes
+            )
+
+            switch success
+            case 0 {
+                // Revert with `Error("VALIDATOR_ERROR")`
+                mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000)
+                mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000)
+                mstore(64, 0x0000000f56414c494441544f525f4552524f5200000000000000000000000000)
+                mstore(96, 0)
+                revert(0, 100)
+            }
+            case 1 {
+                // Signature is valid if call did not revert and returned true
+                isValid := mload(cdStart)
+            }
+        }
+        return isValid;
+    }
 }
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/MixinTransactions.sol b/packages/contracts/src/2.0.0/protocol/Exchange/MixinTransactions.sol
index 821d30279..3a76ca202 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/MixinTransactions.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/MixinTransactions.sol
@@ -28,7 +28,6 @@ contract MixinTransactions is
     MSignatureValidator,
     MTransactions
 {
-
     // Mapping of transaction hash => executed
     // This prevents transactions from being executed more than once.
     mapping (bytes32 => bool) public transactions;
@@ -36,15 +35,6 @@ contract MixinTransactions is
     // Address of current transaction signer
     address public currentContextAddress;
 
-    // Hash for the EIP712 ZeroEx Transaction Schema
-    bytes32 constant internal EIP712_ZEROEX_TRANSACTION_SCHEMA_HASH = keccak256(abi.encodePacked(
-        "ZeroExTransaction(",
-        "uint256 salt,",
-        "address signerAddress,",
-        "bytes data",
-        ")"
-    ));
-
     /// @dev Executes an exchange method call in the context of signer.
     /// @param salt Arbitrary number to ensure uniqueness of transaction hash.
     /// @param signerAddress Address of transaction signer.
@@ -155,7 +145,8 @@ contract MixinTransactions is
         view
         returns (address)
     {
-        address contextAddress = currentContextAddress == address(0) ? msg.sender : currentContextAddress;
+        address currentContextAddress_ = currentContextAddress;
+        address contextAddress = currentContextAddress_ == address(0) ? msg.sender : currentContextAddress_;
         return contextAddress;
     }
 }
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/MixinWrapperFunctions.sol b/packages/contracts/src/2.0.0/protocol/Exchange/MixinWrapperFunctions.sol
index 86194f461..cddff0e5f 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/MixinWrapperFunctions.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/MixinWrapperFunctions.sol
@@ -19,20 +19,23 @@
 pragma solidity 0.4.24;
 pragma experimental ABIEncoderV2;
 
+import "../../utils/ReentrancyGuard/ReentrancyGuard.sol";
 import "./libs/LibMath.sol";
 import "./libs/LibOrder.sol";
 import "./libs/LibFillResults.sol";
 import "./libs/LibAbiEncoder.sol";
 import "./mixins/MExchangeCore.sol";
+import "./mixins/MWrapperFunctions.sol";
 
 
 contract MixinWrapperFunctions is
+    ReentrancyGuard,
     LibMath,
     LibFillResults,
     LibAbiEncoder,
-    MExchangeCore
+    MExchangeCore,
+    MWrapperFunctions
 {
-
     /// @dev Fills the input order. Reverts if exact takerAssetFillAmount not filled.
     /// @param order Order struct containing order specifications.
     /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
@@ -43,17 +46,14 @@ contract MixinWrapperFunctions is
         bytes memory signature
     )
         public
+        nonReentrant
         returns (FillResults memory fillResults)
     {
-        fillResults = fillOrder(
+        fillResults = fillOrKillOrderInternal(
             order,
             takerAssetFillAmount,
             signature
         );
-        require(
-            fillResults.takerAssetFilledAmount == takerAssetFillAmount,
-            "COMPLETE_FILL_FAILED"
-        );
         return fillResults;
     }
 
@@ -81,27 +81,21 @@ contract MixinWrapperFunctions is
         // Delegate to `fillOrder` and handle any exceptions gracefully
         assembly {
             let success := delegatecall(
-                gas,                                // forward all gas, TODO: look into gas consumption of assert/throw
+                gas,                                // forward all gas
                 address,                            // call address of this contract
                 add(fillOrderCalldata, 32),         // pointer to start of input (skip array length in first 32 bytes)
                 mload(fillOrderCalldata),           // length of input
                 fillOrderCalldata,                  // write output over input
                 128                                 // output size is 128 bytes
             )
-            switch success
-            case 0 {
-                mstore(fillResults, 0)
-                mstore(add(fillResults, 32), 0)
-                mstore(add(fillResults, 64), 0)
-                mstore(add(fillResults, 96), 0)
-            }
-            case 1 {
+            if success {
                 mstore(fillResults, mload(fillOrderCalldata))
                 mstore(add(fillResults, 32), mload(add(fillOrderCalldata, 32)))
                 mstore(add(fillResults, 64), mload(add(fillOrderCalldata, 64)))
                 mstore(add(fillResults, 96), mload(add(fillOrderCalldata, 96)))
             }
         }
+        // fillResults values will be 0 by default if call was unsuccessful
         return fillResults;
     }
 
@@ -117,11 +111,12 @@ contract MixinWrapperFunctions is
         bytes[] memory signatures
     )
         public
+        nonReentrant
         returns (FillResults memory totalFillResults)
     {
         uint256 ordersLength = orders.length;
         for (uint256 i = 0; i != ordersLength; i++) {
-            FillResults memory singleFillResults = fillOrder(
+            FillResults memory singleFillResults = fillOrderInternal(
                 orders[i],
                 takerAssetFillAmounts[i],
                 signatures[i]
@@ -143,11 +138,12 @@ contract MixinWrapperFunctions is
         bytes[] memory signatures
     )
         public
+        nonReentrant
         returns (FillResults memory totalFillResults)
     {
         uint256 ordersLength = orders.length;
         for (uint256 i = 0; i != ordersLength; i++) {
-            FillResults memory singleFillResults = fillOrKillOrder(
+            FillResults memory singleFillResults = fillOrKillOrderInternal(
                 orders[i],
                 takerAssetFillAmounts[i],
                 signatures[i]
@@ -195,6 +191,7 @@ contract MixinWrapperFunctions is
         bytes[] memory signatures
     )
         public
+        nonReentrant
         returns (FillResults memory totalFillResults)
     {
         bytes memory takerAssetData = orders[0].takerAssetData;
@@ -210,7 +207,7 @@ contract MixinWrapperFunctions is
             uint256 remainingTakerAssetFillAmount = safeSub(takerAssetFillAmount, totalFillResults.takerAssetFilledAmount);
 
             // Attempt to sell the remaining amount of takerAsset
-            FillResults memory singleFillResults = fillOrder(
+            FillResults memory singleFillResults = fillOrderInternal(
                 orders[i],
                 remainingTakerAssetFillAmount,
                 signatures[i]
@@ -282,6 +279,7 @@ contract MixinWrapperFunctions is
         bytes[] memory signatures
     )
         public
+        nonReentrant
         returns (FillResults memory totalFillResults)
     {
         bytes memory makerAssetData = orders[0].makerAssetData;
@@ -298,14 +296,14 @@ contract MixinWrapperFunctions is
 
             // Convert the remaining amount of makerAsset to buy into remaining amount
             // of takerAsset to sell, assuming entire amount can be sold in the current order
-            uint256 remainingTakerAssetFillAmount = getPartialAmount(
+            uint256 remainingTakerAssetFillAmount = getPartialAmountFloor(
                 orders[i].takerAssetAmount,
                 orders[i].makerAssetAmount,
                 remainingMakerAssetFillAmount
             );
 
             // Attempt to sell the remaining amount of takerAsset
-            FillResults memory singleFillResults = fillOrder(
+            FillResults memory singleFillResults = fillOrderInternal(
                 orders[i],
                 remainingTakerAssetFillAmount,
                 signatures[i]
@@ -350,7 +348,7 @@ contract MixinWrapperFunctions is
 
             // Convert the remaining amount of makerAsset to buy into remaining amount
             // of takerAsset to sell, assuming entire amount can be sold in the current order
-            uint256 remainingTakerAssetFillAmount = getPartialAmount(
+            uint256 remainingTakerAssetFillAmount = getPartialAmountFloor(
                 orders[i].takerAssetAmount,
                 orders[i].makerAssetAmount,
                 remainingMakerAssetFillAmount
@@ -378,10 +376,11 @@ contract MixinWrapperFunctions is
     /// @param orders Array of order specifications.
     function batchCancelOrders(LibOrder.Order[] memory orders)
         public
+        nonReentrant
     {
         uint256 ordersLength = orders.length;
         for (uint256 i = 0; i != ordersLength; i++) {
-            cancelOrder(orders[i]);
+            cancelOrderInternal(orders[i]);
         }
     }
 
@@ -400,4 +399,28 @@ contract MixinWrapperFunctions is
         }
         return ordersInfo;
     }
+
+    /// @dev Fills the input order. Reverts if exact takerAssetFillAmount not filled.
+    /// @param order Order struct containing order specifications.
+    /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
+    /// @param signature Proof that order has been created by maker.
+    function fillOrKillOrderInternal(
+        LibOrder.Order memory order,
+        uint256 takerAssetFillAmount,
+        bytes memory signature
+    )
+        internal
+        returns (FillResults memory fillResults)
+    {
+        fillResults = fillOrderInternal(
+            order,
+            takerAssetFillAmount,
+            signature
+        );
+        require(
+            fillResults.takerAssetFilledAmount == takerAssetFillAmount,
+            "COMPLETE_FILL_FAILED"
+        );
+        return fillResults;
+    }
 }
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibEIP712.sol b/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibEIP712.sol
index b02f7632e..203edc1fd 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibEIP712.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibEIP712.sol
@@ -20,6 +20,7 @@ pragma solidity 0.4.24;
 
 
 contract LibEIP712 {
+
     // EIP191 header for EIP712 prefix
     string constant internal EIP191_HEADER = "\x19\x01";
 
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibFillResults.sol b/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibFillResults.sol
index 1b4181d94..659ae9a69 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibFillResults.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibFillResults.sol
@@ -24,7 +24,6 @@ import "../../../utils/SafeMath/SafeMath.sol";
 contract LibFillResults is
     SafeMath
 {
-
     struct FillResults {
         uint256 makerAssetFilledAmount;  // Total amount of makerAsset(s) filled.
         uint256 takerAssetFilledAmount;  // Total amount of takerAsset(s) filled.
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibMath.sol b/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibMath.sol
index fa09da6ac..c0b85ea10 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibMath.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibMath.sol
@@ -24,13 +24,90 @@ import "../../../utils/SafeMath/SafeMath.sol";
 contract LibMath is
     SafeMath
 {
+    /// @dev Calculates partial value given a numerator and denominator rounded down.
+    ///      Reverts if rounding error is >= 0.1%
+    /// @param numerator Numerator.
+    /// @param denominator Denominator.
+    /// @param target Value to calculate partial of.
+    /// @return Partial value of target rounded down.
+    function safeGetPartialAmountFloor(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        internal
+        pure
+        returns (uint256 partialAmount)
+    {
+        require(
+            denominator > 0,
+            "DIVISION_BY_ZERO"
+        );
+
+        require(
+            !isRoundingErrorFloor(
+                numerator,
+                denominator,
+                target
+            ),
+            "ROUNDING_ERROR"
+        );
+        
+        partialAmount = safeDiv(
+            safeMul(numerator, target),
+            denominator
+        );
+        return partialAmount;
+    }
+
+    /// @dev Calculates partial value given a numerator and denominator rounded down.
+    ///      Reverts if rounding error is >= 0.1%
+    /// @param numerator Numerator.
+    /// @param denominator Denominator.
+    /// @param target Value to calculate partial of.
+    /// @return Partial value of target rounded up.
+    function safeGetPartialAmountCeil(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        internal
+        pure
+        returns (uint256 partialAmount)
+    {
+        require(
+            denominator > 0,
+            "DIVISION_BY_ZERO"
+        );
+
+        require(
+            !isRoundingErrorCeil(
+                numerator,
+                denominator,
+                target
+            ),
+            "ROUNDING_ERROR"
+        );
+        
+        // safeDiv computes `floor(a / b)`. We use the identity (a, b integer):
+        //       ceil(a / b) = floor((a + b - 1) / b)
+        // To implement `ceil(a / b)` using safeDiv.
+        partialAmount = safeDiv(
+            safeAdd(
+                safeMul(numerator, target),
+                safeSub(denominator, 1)
+            ),
+            denominator
+        );
+        return partialAmount;
+    }
 
-    /// @dev Calculates partial value given a numerator and denominator.
+    /// @dev Calculates partial value given a numerator and denominator rounded down.
     /// @param numerator Numerator.
     /// @param denominator Denominator.
     /// @param target Value to calculate partial of.
-    /// @return Partial value of target.
-    function getPartialAmount(
+    /// @return Partial value of target rounded down.
+    function getPartialAmountFloor(
         uint256 numerator,
         uint256 denominator,
         uint256 target
@@ -39,19 +116,110 @@ contract LibMath is
         pure
         returns (uint256 partialAmount)
     {
+        require(
+            denominator > 0,
+            "DIVISION_BY_ZERO"
+        );
+
         partialAmount = safeDiv(
             safeMul(numerator, target),
             denominator
         );
         return partialAmount;
     }
+    
+    /// @dev Calculates partial value given a numerator and denominator rounded down.
+    /// @param numerator Numerator.
+    /// @param denominator Denominator.
+    /// @param target Value to calculate partial of.
+    /// @return Partial value of target rounded up.
+    function getPartialAmountCeil(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        internal
+        pure
+        returns (uint256 partialAmount)
+    {
+        require(
+            denominator > 0,
+            "DIVISION_BY_ZERO"
+        );
 
-    /// @dev Checks if rounding error > 0.1%.
+        // safeDiv computes `floor(a / b)`. We use the identity (a, b integer):
+        //       ceil(a / b) = floor((a + b - 1) / b)
+        // To implement `ceil(a / b)` using safeDiv.
+        partialAmount = safeDiv(
+            safeAdd(
+                safeMul(numerator, target),
+                safeSub(denominator, 1)
+            ),
+            denominator
+        );
+        return partialAmount;
+    }
+    
+    /// @dev Checks if rounding error >= 0.1% when rounding down.
+    /// @param numerator Numerator.
+    /// @param denominator Denominator.
+    /// @param target Value to multiply with numerator/denominator.
+    /// @return Rounding error is present.
+    function isRoundingErrorFloor(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        internal
+        pure
+        returns (bool isError)
+    {
+        require(
+            denominator > 0,
+            "DIVISION_BY_ZERO"
+        );
+        
+        // The absolute rounding error is the difference between the rounded
+        // value and the ideal value. The relative rounding error is the
+        // absolute rounding error divided by the absolute value of the
+        // ideal value. This is undefined when the ideal value is zero.
+        //
+        // The ideal value is `numerator * target / denominator`.
+        // Let's call `numerator * target % denominator` the remainder.
+        // The absolute error is `remainder / denominator`.
+        //
+        // When the ideal value is zero, we require the absolute error to
+        // be zero. Fortunately, this is always the case. The ideal value is
+        // zero iff `numerator == 0` and/or `target == 0`. In this case the
+        // remainder and absolute error are also zero. 
+        if (target == 0 || numerator == 0) {
+            return false;
+        }
+        
+        // Otherwise, we want the relative rounding error to be strictly
+        // less than 0.1%.
+        // The relative error is `remainder / (numerator * target)`.
+        // We want the relative error less than 1 / 1000:
+        //        remainder / (numerator * denominator)  <  1 / 1000
+        // or equivalently:
+        //        1000 * remainder  <  numerator * target
+        // so we have a rounding error iff:
+        //        1000 * remainder  >=  numerator * target
+        uint256 remainder = mulmod(
+            target,
+            numerator,
+            denominator
+        );
+        isError = safeMul(1000, remainder) >= safeMul(numerator, target);
+        return isError;
+    }
+    
+    /// @dev Checks if rounding error >= 0.1% when rounding up.
     /// @param numerator Numerator.
     /// @param denominator Denominator.
     /// @param target Value to multiply with numerator/denominator.
     /// @return Rounding error is present.
-    function isRoundingError(
+    function isRoundingErrorCeil(
         uint256 numerator,
         uint256 denominator,
         uint256 target
@@ -60,16 +228,26 @@ contract LibMath is
         pure
         returns (bool isError)
     {
-        uint256 remainder = mulmod(target, numerator, denominator);
-        if (remainder == 0) {
-            return false; // No rounding error.
+        require(
+            denominator > 0,
+            "DIVISION_BY_ZERO"
+        );
+        
+        // See the comments in `isRoundingError`.
+        if (target == 0 || numerator == 0) {
+            // When either is zero, the ideal value and rounded value are zero
+            // and there is no rounding error. (Although the relative error
+            // is undefined.)
+            return false;
         }
-
-        uint256 errPercentageTimes1000000 = safeDiv(
-            safeMul(remainder, 1000000),
-            safeMul(numerator, target)
+        // Compute remainder as before
+        uint256 remainder = mulmod(
+            target,
+            numerator,
+            denominator
         );
-        isError = errPercentageTimes1000000 > 1000;
+        remainder = safeSub(denominator, remainder) % denominator;
+        isError = safeMul(1000, remainder) >= safeMul(numerator, target);
         return isError;
     }
 }
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibOrder.sol b/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibOrder.sol
index 68f4f5f1b..0fe7c2161 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibOrder.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibOrder.sol
@@ -24,7 +24,6 @@ import "./LibEIP712.sol";
 contract LibOrder is
     LibEIP712
 {
-
     // Hash for the EIP712 Order Schema
     bytes32 constant internal EIP712_ORDER_SCHEMA_HASH = keccak256(abi.encodePacked(
         "Order(",
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MAssetProxyDispatcher.sol b/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
index c6904300a..0ddfca270 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
@@ -24,7 +24,6 @@ import "../interfaces/IAssetProxyDispatcher.sol";
 contract MAssetProxyDispatcher is
     IAssetProxyDispatcher
 {
-
     // Logs registration of new asset proxy
     event AssetProxyRegistered(
         bytes4 id,              // Id of new registered AssetProxy.
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MExchangeCore.sol b/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MExchangeCore.sol
index c165b647c..742499568 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MExchangeCore.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MExchangeCore.sol
@@ -59,6 +59,24 @@ contract MExchangeCore is
         uint256 orderEpoch                    // Orders with specified makerAddress and senderAddress with a salt less than this value are considered cancelled.
     );
 
+    /// @dev Fills the input order.
+    /// @param order Order struct containing order specifications.
+    /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
+    /// @param signature Proof that order has been created by maker.
+    /// @return Amounts filled and fees paid by maker and taker.
+    function fillOrderInternal(
+        LibOrder.Order memory order,
+        uint256 takerAssetFillAmount,
+        bytes memory signature
+    )
+        internal
+        returns (LibFillResults.FillResults memory fillResults);
+
+    /// @dev After calling, the order can not be filled anymore.
+    /// @param order Order struct containing order specifications.
+    function cancelOrderInternal(LibOrder.Order memory order)
+        internal;
+
     /// @dev Updates state with results of a fill order.
     /// @param order that was filled.
     /// @param takerAddress Address of taker who filled the order.
@@ -83,21 +101,33 @@ contract MExchangeCore is
         bytes32 orderHash
     )
         internal;
-
+    
     /// @dev Validates context for fillOrder. Succeeds or throws.
     /// @param order to be filled.
-    /// @param orderInfo Status, orderHash, and amount already filled of order.
+    /// @param orderInfo OrderStatus, orderHash, and amount already filled of order.
     /// @param takerAddress Address of order taker.
+    /// @param signature Proof that the orders was created by its maker.
+    function assertFillableOrder(
+        LibOrder.Order memory order,
+        LibOrder.OrderInfo memory orderInfo,
+        address takerAddress,
+        bytes memory signature
+    )
+        internal
+        view;
+    
+    /// @dev Validates context for fillOrder. Succeeds or throws.
+    /// @param order to be filled.
+    /// @param orderInfo Status, orderHash, and amount already filled of order.
     /// @param takerAssetFillAmount Desired amount of order to fill by taker.
     /// @param takerAssetFilledAmount Amount of takerAsset that will be filled.
-    /// @param signature Proof that the orders was created by its maker.
+    /// @param makerAssetFilledAmount Amount of makerAsset that will be transfered.
     function assertValidFill(
         LibOrder.Order memory order,
         LibOrder.OrderInfo memory orderInfo,
-        address takerAddress,
         uint256 takerAssetFillAmount,
         uint256 takerAssetFilledAmount,
-        bytes memory signature
+        uint256 makerAssetFilledAmount
     )
         internal
         view;
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MMatchOrders.sol b/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MMatchOrders.sol
index a31ec1585..96fa34bc0 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MMatchOrders.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MMatchOrders.sol
@@ -26,7 +26,6 @@ import "../interfaces/IMatchOrders.sol";
 contract MMatchOrders is
     IMatchOrders
 {
-
     /// @dev Validates context for matchOrders. Succeeds or throws.
     /// @param leftOrder First order to match.
     /// @param rightOrder Second order to match.
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MSignatureValidator.sol b/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MSignatureValidator.sol
index f14f2ba00..1fe88b908 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MSignatureValidator.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MSignatureValidator.sol
@@ -36,11 +36,40 @@ contract MSignatureValidator is
         Invalid,         // 0x01
         EIP712,          // 0x02
         EthSign,         // 0x03
-        Caller,          // 0x04
-        Wallet,          // 0x05
-        Validator,       // 0x06
-        PreSigned,       // 0x07
-        Trezor,          // 0x08
-        NSignatureTypes  // 0x09, number of signature types. Always leave at end.
+        Wallet,          // 0x04
+        Validator,       // 0x05
+        PreSigned,       // 0x06
+        NSignatureTypes  // 0x07, number of signature types. Always leave at end.
     }
+
+    /// @dev Verifies signature using logic defined by Wallet contract.
+    /// @param hash Any 32 byte hash.
+    /// @param walletAddress Address that should have signed the given hash
+    ///                      and defines its own signature verification method.
+    /// @param signature Proof that the hash has been signed by signer.
+    /// @return True if the address recovered from the provided signature matches the input signer address.
+    function isValidWalletSignature(
+        bytes32 hash,
+        address walletAddress,
+        bytes signature
+    )
+        internal
+        view
+        returns (bool isValid);
+
+    /// @dev Verifies signature using logic defined by Validator contract.
+    /// @param validatorAddress Address of validator contract.
+    /// @param hash Any 32 byte hash.
+    /// @param signerAddress Address that should have signed the given hash.
+    /// @param signature Proof that the hash has been signed by signer.
+    /// @return True if the address recovered from the provided signature matches the input signer address.
+    function isValidValidatorSignature(
+        address validatorAddress,
+        bytes32 hash,
+        address signerAddress,
+        bytes signature
+    )
+        internal
+        view
+        returns (bool isValid);
 }
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MTransactions.sol b/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MTransactions.sol
index f2b5e4b16..4f61a4945 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MTransactions.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MTransactions.sol
@@ -23,6 +23,28 @@ import "../interfaces/ITransactions.sol";
 contract MTransactions is
     ITransactions
 {
+    // Hash for the EIP712 ZeroEx Transaction Schema
+    bytes32 constant internal EIP712_ZEROEX_TRANSACTION_SCHEMA_HASH = keccak256(abi.encodePacked(
+        "ZeroExTransaction(",
+        "uint256 salt,",
+        "address signerAddress,",
+        "bytes data",
+        ")"
+    ));
+
+    /// @dev Calculates EIP712 hash of the Transaction.
+    /// @param salt Arbitrary number to ensure uniqueness of transaction hash.
+    /// @param signerAddress Address of transaction signer.
+    /// @param data AbiV2 encoded calldata.
+    /// @return EIP712 hash of the Transaction.
+    function hashZeroExTransaction(
+        uint256 salt,
+        address signerAddress,
+        bytes memory data
+    )
+        internal
+        pure
+        returns (bytes32 result);
 
     /// @dev The current function will be called in the context of this address (either 0x transaction signer or `msg.sender`).
     ///      If calling a fill function, this address will represent the taker.
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MWrapperFunctions.sol b/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MWrapperFunctions.sol
new file mode 100644
index 000000000..4adfbde01
--- /dev/null
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MWrapperFunctions.sol
@@ -0,0 +1,41 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity 0.4.24;
+pragma experimental ABIEncoderV2;
+
+import "../libs/LibOrder.sol";
+import "../libs/LibFillResults.sol";
+import "../interfaces/IWrapperFunctions.sol";
+
+
+contract MWrapperFunctions is 
+    IWrapperFunctions
+{
+    /// @dev Fills the input order. Reverts if exact takerAssetFillAmount not filled.
+    /// @param order LibOrder.Order struct containing order specifications.
+    /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
+    /// @param signature Proof that order has been created by maker.
+    function fillOrKillOrderInternal(
+        LibOrder.Order memory order,
+        uint256 takerAssetFillAmount,
+        bytes memory signature
+    )
+        internal
+        returns (LibFillResults.FillResults memory fillResults);
+}
diff --git a/packages/contracts/src/2.0.0/test/DummyERC20Token/DummyERC20Token.sol b/packages/contracts/src/2.0.0/test/DummyERC20Token/DummyERC20Token.sol
index 9272b18a8..412c5d1ad 100644
--- a/packages/contracts/src/2.0.0/test/DummyERC20Token/DummyERC20Token.sol
+++ b/packages/contracts/src/2.0.0/test/DummyERC20Token/DummyERC20Token.sol
@@ -18,17 +18,18 @@
 
 pragma solidity 0.4.24;
 
-import "../Mintable/Mintable.sol";
 import "../../utils/Ownable/Ownable.sol";
+import "../../tokens/ERC20Token/MintableERC20Token.sol";
 
 
 contract DummyERC20Token is 
-    Mintable,
-    Ownable
+    Ownable,
+    MintableERC20Token
 {
     string public name;
     string public symbol;
     uint256 public decimals;
+    uint256 public constant MAX_MINT_AMOUNT = 10000000000000000000000;
 
     constructor (
         string _name,
@@ -41,20 +42,36 @@ contract DummyERC20Token is
         name = _name;
         symbol = _symbol;
         decimals = _decimals;
-        totalSupply = _totalSupply;
+        _totalSupply = _totalSupply;
         balances[msg.sender] = _totalSupply;
     }
 
+    /// @dev Sets the balance of target address
+    /// @param _target Address or which balance will be updated
+    /// @param _value New balance of target address
     function setBalance(address _target, uint256 _value)
-        public
+        external
         onlyOwner
     {
-        uint256 currBalance = balanceOf(_target);
+        uint256 currBalance = balances[_target];
         if (_value < currBalance) {
-            totalSupply = safeSub(totalSupply, safeSub(currBalance, _value));
+            _totalSupply = safeSub(_totalSupply, safeSub(currBalance, _value));
         } else {
-            totalSupply = safeAdd(totalSupply, safeSub(_value, currBalance));
+            _totalSupply = safeAdd(_totalSupply, safeSub(_value, currBalance));
         }
         balances[_target] = _value;
     }
+
+    /// @dev Mints new tokens for sender
+    /// @param _value Amount of tokens to mint
+    function mint(uint256 _value)
+        external
+    {
+        require(
+            _value <= MAX_MINT_AMOUNT,
+            "VALUE_TOO_LARGE"
+        );
+
+        _mint(msg.sender, _value);
+    }
 }
diff --git a/packages/contracts/src/2.0.0/test/DummyERC20Token/DummyMultipleReturnERC20Token.sol b/packages/contracts/src/2.0.0/test/DummyERC20Token/DummyMultipleReturnERC20Token.sol
new file mode 100644
index 000000000..733d4437e
--- /dev/null
+++ b/packages/contracts/src/2.0.0/test/DummyERC20Token/DummyMultipleReturnERC20Token.sol
@@ -0,0 +1,69 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity 0.4.24;
+
+import "./DummyERC20Token.sol";
+
+
+// solhint-disable no-empty-blocks
+contract DummyMultipleReturnERC20Token is
+    DummyERC20Token
+{
+    constructor (
+        string _name,
+        string _symbol,
+        uint256 _decimals,
+        uint256 _totalSupply
+    )
+        public
+        DummyERC20Token(
+            _name,
+            _symbol,
+            _decimals,
+            _totalSupply
+        )
+    {}
+
+    /// @dev send `value` token to `to` from `from` on the condition it is approved by `from`
+    /// @param _from The address of the sender
+    /// @param _to The address of the recipient
+    /// @param _value The amount of token to be transferred
+    function transferFrom(
+        address _from,
+        address _to,
+        uint256 _value
+    )
+        external
+        returns (bool)
+    {
+        emit Transfer(
+            _from,
+            _to,
+            _value
+        );
+
+        // HACK: This contract will not compile if we remove `returns (bool)`, so we manually return 64 bytes (equiavalent to true, true)
+        assembly {
+            mstore(0, 1)
+            mstore(32, 1)
+            return(0, 64)
+        }
+    }
+}
+
diff --git a/packages/contracts/src/2.0.0/test/DummyERC20Token/DummyNoReturnERC20Token.sol b/packages/contracts/src/2.0.0/test/DummyERC20Token/DummyNoReturnERC20Token.sol
new file mode 100644
index 000000000..e16825a16
--- /dev/null
+++ b/packages/contracts/src/2.0.0/test/DummyERC20Token/DummyNoReturnERC20Token.sol
@@ -0,0 +1,115 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity 0.4.24;
+
+import "./DummyERC20Token.sol";
+
+
+// solhint-disable no-empty-blocks
+contract DummyNoReturnERC20Token is
+    DummyERC20Token
+{
+    constructor (
+        string _name,
+        string _symbol,
+        uint256 _decimals,
+        uint256 _totalSupply
+    )
+        public
+        DummyERC20Token(
+            _name,
+            _symbol,
+            _decimals,
+            _totalSupply
+        )
+    {}
+
+    /// @dev send `value` token to `to` from `msg.sender`
+    /// @param _to The address of the recipient
+    /// @param _value The amount of token to be transferred
+    function transfer(address _to, uint256 _value)
+        external
+        returns (bool)
+    {
+        require(
+            balances[msg.sender] >= _value,
+            "ERC20_INSUFFICIENT_BALANCE"
+        );
+        require(
+            balances[_to] + _value >= balances[_to],
+            "UINT256_OVERFLOW"
+        );
+
+        balances[msg.sender] -= _value;
+        balances[_to] += _value;
+
+        emit Transfer(
+            msg.sender,
+            _to,
+            _value
+        );
+
+        // HACK: This contract will not compile if we remove `returns (bool)`, so we manually return no data
+        assembly {
+            return(0, 0)
+        }
+    }
+
+    /// @dev send `value` token to `to` from `from` on the condition it is approved by `from`
+    /// @param _from The address of the sender
+    /// @param _to The address of the recipient
+    /// @param _value The amount of token to be transferred
+    function transferFrom(
+        address _from,
+        address _to,
+        uint256 _value
+    )
+        external
+        returns (bool)
+    {
+        require(
+            balances[_from] >= _value,
+            "ERC20_INSUFFICIENT_BALANCE"
+        );
+        require(
+            allowed[_from][msg.sender] >= _value,
+            "ERC20_INSUFFICIENT_ALLOWANCE"
+        );
+        require(
+            balances[_to] + _value >= balances[_to],
+            "UINT256_OVERFLOW"
+        );
+
+        balances[_to] += _value;
+        balances[_from] -= _value;
+        allowed[_from][msg.sender] -= _value;
+    
+        emit Transfer(
+            _from,
+            _to,
+            _value
+        );
+
+        // HACK: This contract will not compile if we remove `returns (bool)`, so we manually return no data
+        assembly {
+            return(0, 0)
+        }
+    }
+}
+
diff --git a/packages/contracts/src/2.0.0/test/DummyERC721Receiver/DummyERC721Receiver.sol b/packages/contracts/src/2.0.0/test/DummyERC721Receiver/DummyERC721Receiver.sol
index 5dce74a14..6c8371559 100644
--- a/packages/contracts/src/2.0.0/test/DummyERC721Receiver/DummyERC721Receiver.sol
+++ b/packages/contracts/src/2.0.0/test/DummyERC721Receiver/DummyERC721Receiver.sol
@@ -1,26 +1,19 @@
 /*
-The MIT License (MIT)
 
-Copyright (c) 2016 Smart Contract Solutions, Inc.
+  Copyright 2018 ZeroEx Intl.
 
-Permission is hereby granted, free of charge, to any person obtaining
-a copy of this software and associated documentation files (the
-"Software"), to deal in the Software without restriction, including
-without limitation the rights to use, copy, modify, merge, publish,
-distribute, sublicense, and/or sell copies of the Software, and to
-permit persons to whom the Software is furnished to do so, subject to
-the following conditions:
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
 
-The above copyright notice and this permission notice shall be included
-in all copies or substantial portions of the Software.
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
 
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
-OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
-MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
-IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
-CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
-TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
-SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
 
 pragma solidity 0.4.24;
@@ -31,34 +24,44 @@ import "../../tokens/ERC721Token/IERC721Receiver.sol";
 contract DummyERC721Receiver is
     IERC721Receiver
 {
+    // Function selector for ERC721Receiver.onERC721Received
+    // 0x150b7a02
+    bytes4 constant internal ERC721_RECEIVED = bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"));
 
     event TokenReceived(
+        address operator,
         address from,
         uint256 tokenId,
         bytes data
     );
 
-    /**
-    * @notice Handle the receipt of an NFT
-    * @dev The ERC721 smart contract calls this function on the recipient
-    *  after a `safetransfer`. This function MAY throw to revert and reject the
-    *  transfer. This function MUST use 50,000 gas or less. Return of other
-    *  than the magic value MUST result in the transaction being reverted.
-    *  Note: the contract address is always the message sender.
-    * @param _from The sending address
-    * @param _tokenId The NFT identifier which is being transfered
-    * @param _data Additional data with no specified format
-    * @return `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`
-    */
+    /// @notice Handle the receipt of an NFT
+    /// @dev The ERC721 smart contract calls this function on the recipient
+    ///      after a `transfer`. This function MAY throw to revert and reject the
+    ///      transfer. Return of other than the magic value MUST result in the
+    ///      transaction being reverted.
+    ///      Note: the contract address is always the message sender.
+    /// @param _operator The address which called `safeTransferFrom` function
+    /// @param _from The address which previously owned the token
+    /// @param _tokenId The NFT identifier which is being transferred
+    /// @param _data Additional data with no specified format
+    /// @return `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
+    ///         unless throwing
     function onERC721Received(
+        address _operator,
         address _from,
         uint256 _tokenId,
         bytes _data
     )
-        public
+        external
         returns (bytes4)
     {
-        emit TokenReceived(_from, _tokenId, _data);
+        emit TokenReceived(
+            _operator,
+            _from,
+            _tokenId,
+            _data
+        );
         return ERC721_RECEIVED;
     }
 }
diff --git a/packages/contracts/src/2.0.0/test/DummyERC721Receiver/InvalidERC721Receiver.sol b/packages/contracts/src/2.0.0/test/DummyERC721Receiver/InvalidERC721Receiver.sol
new file mode 100644
index 000000000..309633bf5
--- /dev/null
+++ b/packages/contracts/src/2.0.0/test/DummyERC721Receiver/InvalidERC721Receiver.sol
@@ -0,0 +1,66 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity 0.4.24;
+
+import "../../tokens/ERC721Token/IERC721Receiver.sol";
+
+
+contract InvalidERC721Receiver is
+    IERC721Receiver
+{
+    // Actual function signature is `onERC721Received(address,address,uint256,bytes)`
+    bytes4 constant internal INVALID_ERC721_RECEIVED = bytes4(keccak256("onERC721Received(address,uint256,bytes)"));
+
+    event TokenReceived(
+        address operator,
+        address from,
+        uint256 tokenId,
+        bytes data
+    );
+
+    /// @notice Handle the receipt of an NFT
+    /// @dev The ERC721 smart contract calls this function on the recipient
+    ///      after a `transfer`. This function MAY throw to revert and reject the
+    ///      transfer. Return of other than the magic value MUST result in the
+    ///      transaction being reverted.
+    ///      Note: the contract address is always the message sender.
+    /// @param _operator The address which called `safeTransferFrom` function
+    /// @param _from The address which previously owned the token
+    /// @param _tokenId The NFT identifier which is being transferred
+    /// @param _data Additional data with no specified format
+    /// @return `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
+    ///         unless throwing
+    function onERC721Received(
+        address _operator,
+        address _from,
+        uint256 _tokenId,
+        bytes _data
+    )
+        external
+        returns (bytes4)
+    {
+        emit TokenReceived(
+            _operator,
+            _from,
+            _tokenId,
+            _data
+        );
+        return INVALID_ERC721_RECEIVED;
+    }
+}
diff --git a/packages/contracts/src/2.0.0/test/DummyERC721Token/DummyERC721Token.sol b/packages/contracts/src/2.0.0/test/DummyERC721Token/DummyERC721Token.sol
index 627746a52..ac9068d1d 100644
--- a/packages/contracts/src/2.0.0/test/DummyERC721Token/DummyERC721Token.sol
+++ b/packages/contracts/src/2.0.0/test/DummyERC721Token/DummyERC721Token.sol
@@ -18,59 +18,46 @@
 
 pragma solidity 0.4.24;
 
-import "../../tokens/ERC721Token/ERC721Token.sol";
+import "../../tokens/ERC721Token/MintableERC721Token.sol";
 import "../../utils/Ownable/Ownable.sol";
 
 
 // solhint-disable no-empty-blocks
 contract DummyERC721Token is
     Ownable,
-    ERC721Token
+    MintableERC721Token
 {
+    string public name;
+    string public symbol;
 
-    /**
-    * @dev Constructor passes its arguments to the base ERC721Token constructor
-    * @param name of token
-    * @param symbol of token
-    */
     constructor (
-        string name,
-        string symbol
+        string _name,
+        string _symbol
     )
         public
-        ERC721Token(name, symbol)
-    {}
+    {
+        name = _name;
+        symbol = _symbol;
+    }
 
-    /**
-    * @dev Function to mint a new token
-    * @dev Reverts if the given token ID already exists
-    * @param to address the beneficiary that will own the minted token
-    * @param tokenId uint256 ID of the token to be minted by the msg.sender
-    */
-    function mint(address to, uint256 tokenId)
-        public
-        onlyOwner
+    /// @dev Function to mint a new token
+    ///      Reverts if the given token ID already exists
+    /// @param _to Address of the beneficiary that will own the minted token
+    /// @param _tokenId ID of the token to be minted by the msg.sender    
+    function mint(address _to, uint256 _tokenId)
+        external
     {
-        require(
-            !exists(tokenId),
-            "Token with tokenId already exists."
-        );
-        _mint(to, tokenId);
+        _mint(_to, _tokenId);
     }
 
-    /**
-    * @dev Function to burn a token
-    * @dev Reverts if the given token ID doesn't exist
-    * @param tokenId uint256 ID of the token to be minted by the msg.sender
-    */
-    function burn(address owner, uint256 tokenId)
-        public
+    /// @dev Function to burn a token
+    ///      Reverts if the given token ID doesn't exist or not called by contract owner
+    /// @param _owner Owner of token with given token ID
+    /// @param _tokenId ID of the token to be burned by the msg.sender
+    function burn(address _owner, uint256 _tokenId)
+        external
         onlyOwner
     {
-        require(
-            exists(tokenId),
-            "Token with tokenId does not exist."
-        );
-        _burn(owner, tokenId);
+        _burn(_owner, _tokenId);
     }
 }
diff --git a/packages/contracts/src/2.0.0/test/ReentrantERC20Token/ReentrantERC20Token.sol b/packages/contracts/src/2.0.0/test/ReentrantERC20Token/ReentrantERC20Token.sol
new file mode 100644
index 000000000..99dd47a78
--- /dev/null
+++ b/packages/contracts/src/2.0.0/test/ReentrantERC20Token/ReentrantERC20Token.sol
@@ -0,0 +1,188 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity 0.4.24;
+pragma experimental ABIEncoderV2;
+
+import "../../utils/LibBytes/LibBytes.sol";
+import "../../tokens/ERC20Token/ERC20Token.sol";
+import "../../protocol/Exchange/interfaces/IExchange.sol";
+import "../../protocol/Exchange/libs/LibOrder.sol";
+
+
+// solhint-disable no-unused-vars
+contract ReentrantERC20Token is
+    ERC20Token
+{
+    using LibBytes for bytes;
+
+    // solhint-disable-next-line var-name-mixedcase
+    IExchange internal EXCHANGE;
+
+    bytes internal constant REENTRANCY_ILLEGAL_REVERT_REASON = abi.encodeWithSelector(
+        bytes4(keccak256("Error(string)")),
+        "REENTRANCY_ILLEGAL"
+    );
+
+    // All of these functions are potentially vulnerable to reentrancy
+    // We do not test any "noThrow" functions because `fillOrderNoThrow` makes a delegatecall to `fillOrder`
+    enum ExchangeFunction {
+        FILL_ORDER,
+        FILL_OR_KILL_ORDER,
+        BATCH_FILL_ORDERS,
+        BATCH_FILL_OR_KILL_ORDERS,
+        MARKET_BUY_ORDERS,
+        MARKET_SELL_ORDERS,
+        MATCH_ORDERS,
+        CANCEL_ORDER,
+        BATCH_CANCEL_ORDERS,
+        CANCEL_ORDERS_UP_TO,
+        SET_SIGNATURE_VALIDATOR_APPROVAL
+    }
+
+    uint8 internal currentFunctionId = 0;
+
+    constructor (address _exchange)
+        public
+    {
+        EXCHANGE = IExchange(_exchange);
+    }
+
+    /// @dev Set the current function that will be called when `transferFrom` is called.
+    /// @param _currentFunctionId Id that corresponds to function name.
+    function setCurrentFunction(uint8 _currentFunctionId)
+        external
+    {
+        currentFunctionId = _currentFunctionId;
+    }
+
+    /// @dev A version of `transferFrom` that attempts to reenter the Exchange contract.
+    /// @param _from The address of the sender
+    /// @param _to The address of the recipient
+    /// @param _value The amount of token to be transferred
+    function transferFrom(
+        address _from,
+        address _to,
+        uint256 _value
+    )
+        external
+        returns (bool)
+    {
+        // This order would normally be invalid, but it will be used strictly for testing reentrnacy.
+        // Any reentrancy checks will happen before any other checks that invalidate the order.
+        LibOrder.Order memory order;
+
+        // Initialize remaining null parameters
+        bytes memory signature;
+        LibOrder.Order[] memory orders;
+        uint256[] memory takerAssetFillAmounts;
+        bytes[] memory signatures;
+        bytes memory calldata;
+
+        // Create calldata for function that corresponds to currentFunctionId
+        if (currentFunctionId == uint8(ExchangeFunction.FILL_ORDER)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.fillOrder.selector,
+                order,
+                0,
+                signature
+            );
+        } else if (currentFunctionId == uint8(ExchangeFunction.FILL_OR_KILL_ORDER)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.fillOrKillOrder.selector,
+                order,
+                0,
+                signature
+            );
+        } else if (currentFunctionId == uint8(ExchangeFunction.BATCH_FILL_ORDERS)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.batchFillOrders.selector,
+                orders,
+                takerAssetFillAmounts,
+                signatures
+            );
+        } else if (currentFunctionId == uint8(ExchangeFunction.BATCH_FILL_OR_KILL_ORDERS)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.batchFillOrKillOrders.selector,
+                orders,
+                takerAssetFillAmounts,
+                signatures
+            );
+        } else if (currentFunctionId == uint8(ExchangeFunction.MARKET_BUY_ORDERS)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.marketBuyOrders.selector,
+                orders,
+                0,
+                signatures
+            );
+        } else if (currentFunctionId == uint8(ExchangeFunction.MARKET_SELL_ORDERS)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.marketSellOrders.selector,
+                orders,
+                0,
+                signatures
+            );
+        } else if (currentFunctionId == uint8(ExchangeFunction.MATCH_ORDERS)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.matchOrders.selector,
+                order,
+                order,
+                signature,
+                signature
+            );
+        } else if (currentFunctionId == uint8(ExchangeFunction.CANCEL_ORDER)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.cancelOrder.selector,
+                order
+            );
+        } else if (currentFunctionId == uint8(ExchangeFunction.BATCH_CANCEL_ORDERS)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.batchCancelOrders.selector,
+                orders
+            );
+        } else if (currentFunctionId == uint8(ExchangeFunction.CANCEL_ORDERS_UP_TO)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.cancelOrdersUpTo.selector,
+                0
+            );
+        } else if (currentFunctionId == uint8(ExchangeFunction.SET_SIGNATURE_VALIDATOR_APPROVAL)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.setSignatureValidatorApproval.selector,
+                address(0),
+                false
+            );
+        }
+
+        // Call Exchange function, swallow error
+        address(EXCHANGE).call(calldata);
+
+        // Revert reason is 100 bytes
+        bytes memory returnData = new bytes(100);
+
+        // Copy return data
+        assembly {
+            returndatacopy(add(returnData, 32), 0, 100)
+        }
+
+        // Revert if function reverted with REENTRANCY_ILLEGAL error
+        require(!REENTRANCY_ILLEGAL_REVERT_REASON.equals(returnData));
+
+        // Transfer will return true if function failed for any other reason
+        return true;
+    }
+}
\ No newline at end of file
diff --git a/packages/contracts/src/2.0.0/test/TestAssetProxyOwner/TestAssetProxyOwner.sol b/packages/contracts/src/2.0.0/test/TestAssetProxyOwner/TestAssetProxyOwner.sol
index 75e782d43..52c66cb56 100644
--- a/packages/contracts/src/2.0.0/test/TestAssetProxyOwner/TestAssetProxyOwner.sol
+++ b/packages/contracts/src/2.0.0/test/TestAssetProxyOwner/TestAssetProxyOwner.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity 0.4.10;
+pragma solidity 0.4.24;
 
 import "../../protocol/AssetProxyOwner/AssetProxyOwner.sol";
 
@@ -25,8 +25,7 @@ import "../../protocol/AssetProxyOwner/AssetProxyOwner.sol";
 contract TestAssetProxyOwner is
     AssetProxyOwner
 {
-
-    function TestAssetProxyOwner(
+    constructor (
         address[] memory _owners,
         address[] memory _assetProxyContracts,
         uint256 _required,
@@ -38,6 +37,7 @@ contract TestAssetProxyOwner is
     
     function testValidRemoveAuthorizedAddressAtIndexTx(uint256 id)
         public
+        view
         validRemoveAuthorizedAddressAtIndexTx(id)
         returns (bool)
     {
@@ -50,23 +50,9 @@ contract TestAssetProxyOwner is
     /// @return Successful if data is a call to `removeAuthorizedAddressAtIndex`.
     function isFunctionRemoveAuthorizedAddressAtIndex(bytes memory data)
         public
+        pure
         returns (bool)
     {
-        return readBytes4(data, 0) == REMOVE_AUTHORIZED_ADDRESS_AT_INDEX_SELECTOR;
-    }
-
-    /// @dev Reads an unpadded bytes4 value from a position in a byte array.
-    /// @param b Byte array containing a bytes4 value.
-    /// @param index Index in byte array of bytes4 value.
-    /// @return bytes4 value from byte array.
-    function publicReadBytes4(
-        bytes memory b,
-        uint256 index
-    )
-        public
-        returns (bytes4 result)
-    {
-        result = readBytes4(b, index);
-        return result;
+        return data.readBytes4(0) == REMOVE_AUTHORIZED_ADDRESS_AT_INDEX_SELECTOR;
     }
 }
diff --git a/packages/contracts/src/2.0.0/test/TestExchangeInternals/TestExchangeInternals.sol b/packages/contracts/src/2.0.0/test/TestExchangeInternals/TestExchangeInternals.sol
index d9cec9edc..27187f8f8 100644
--- a/packages/contracts/src/2.0.0/test/TestExchangeInternals/TestExchangeInternals.sol
+++ b/packages/contracts/src/2.0.0/test/TestExchangeInternals/TestExchangeInternals.sol
@@ -63,11 +63,12 @@ contract TestExchangeInternals is
     }
 
     /// @dev Calculates partial value given a numerator and denominator.
+    ///      Reverts if rounding error is >= 0.1%
     /// @param numerator Numerator.
     /// @param denominator Denominator.
     /// @param target Value to calculate partial of.
     /// @return Partial value of target.
-    function publicGetPartialAmount(
+    function publicSafeGetPartialAmountFloor(
         uint256 numerator,
         uint256 denominator,
         uint256 target
@@ -76,15 +77,84 @@ contract TestExchangeInternals is
         pure
         returns (uint256 partialAmount)
     {
-        return getPartialAmount(numerator, denominator, target);
+        return safeGetPartialAmountFloor(numerator, denominator, target);
     }
 
-    /// @dev Checks if rounding error > 0.1%.
+    /// @dev Calculates partial value given a numerator and denominator.
+    ///      Reverts if rounding error is >= 0.1%
+    /// @param numerator Numerator.
+    /// @param denominator Denominator.
+    /// @param target Value to calculate partial of.
+    /// @return Partial value of target.
+    function publicSafeGetPartialAmountCeil(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        public
+        pure
+        returns (uint256 partialAmount)
+    {
+        return safeGetPartialAmountCeil(numerator, denominator, target);
+    }
+
+    /// @dev Calculates partial value given a numerator and denominator.
+    /// @param numerator Numerator.
+    /// @param denominator Denominator.
+    /// @param target Value to calculate partial of.
+    /// @return Partial value of target.
+    function publicGetPartialAmountFloor(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        public
+        pure
+        returns (uint256 partialAmount)
+    {
+        return getPartialAmountFloor(numerator, denominator, target);
+    }
+
+    /// @dev Calculates partial value given a numerator and denominator.
+    /// @param numerator Numerator.
+    /// @param denominator Denominator.
+    /// @param target Value to calculate partial of.
+    /// @return Partial value of target.
+    function publicGetPartialAmountCeil(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        public
+        pure
+        returns (uint256 partialAmount)
+    {
+        return getPartialAmountCeil(numerator, denominator, target);
+    }
+
+    /// @dev Checks if rounding error >= 0.1%.
+    /// @param numerator Numerator.
+    /// @param denominator Denominator.
+    /// @param target Value to multiply with numerator/denominator.
+    /// @return Rounding error is present.
+    function publicIsRoundingErrorFloor(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        public
+        pure
+        returns (bool isError)
+    {
+        return isRoundingErrorFloor(numerator, denominator, target);
+    }
+
+    /// @dev Checks if rounding error >= 0.1%.
     /// @param numerator Numerator.
     /// @param denominator Denominator.
     /// @param target Value to multiply with numerator/denominator.
     /// @return Rounding error is present.
-    function publicIsRoundingError(
+    function publicIsRoundingErrorCeil(
         uint256 numerator,
         uint256 denominator,
         uint256 target
@@ -93,7 +163,7 @@ contract TestExchangeInternals is
         pure
         returns (bool isError)
     {
-        return isRoundingError(numerator, denominator, target);
+        return isRoundingErrorCeil(numerator, denominator, target);
     }
  
     /// @dev Updates state with results of a fill order.
diff --git a/packages/contracts/src/2.0.0/test/TestLibs/TestLibs.sol b/packages/contracts/src/2.0.0/test/TestLibs/TestLibs.sol
index 4a99dd9c1..a10f981fc 100644
--- a/packages/contracts/src/2.0.0/test/TestLibs/TestLibs.sol
+++ b/packages/contracts/src/2.0.0/test/TestLibs/TestLibs.sol
@@ -31,7 +31,6 @@ contract TestLibs is
     LibFillResults,
     LibAbiEncoder
 {
-
     function publicAbiEncodeFillOrder(
         Order memory order,
         uint256 takerAssetFillAmount,
@@ -49,7 +48,24 @@ contract TestLibs is
         return fillOrderCalldata;
     }
 
-    function publicGetPartialAmount(
+    function publicGetPartialAmountFloor(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        public
+        pure
+        returns (uint256 partialAmount)
+    {
+        partialAmount = getPartialAmountFloor(
+            numerator,
+            denominator,
+            target
+        );
+        return partialAmount;
+    }
+
+    function publicGetPartialAmountCeil(
         uint256 numerator,
         uint256 denominator,
         uint256 target
@@ -58,7 +74,7 @@ contract TestLibs is
         pure
         returns (uint256 partialAmount)
     {
-        partialAmount = getPartialAmount(
+        partialAmount = getPartialAmountCeil(
             numerator,
             denominator,
             target
@@ -66,7 +82,24 @@ contract TestLibs is
         return partialAmount;
     }
 
-    function publicIsRoundingError(
+    function publicIsRoundingErrorFloor(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        public
+        pure
+        returns (bool isError)
+    {
+        isError = isRoundingErrorFloor(
+            numerator,
+            denominator,
+            target
+        );
+        return isError;
+    }
+
+    function publicIsRoundingErrorCeil(
         uint256 numerator,
         uint256 denominator,
         uint256 target
@@ -75,7 +108,7 @@ contract TestLibs is
         pure
         returns (bool isError)
     {
-        isError = isRoundingError(
+        isError = isRoundingErrorCeil(
             numerator,
             denominator,
             target
diff --git a/packages/contracts/src/2.0.0/test/TestSignatureValidator/TestSignatureValidator.sol b/packages/contracts/src/2.0.0/test/TestSignatureValidator/TestSignatureValidator.sol
index e1a610469..ea3e2de59 100644
--- a/packages/contracts/src/2.0.0/test/TestSignatureValidator/TestSignatureValidator.sol
+++ b/packages/contracts/src/2.0.0/test/TestSignatureValidator/TestSignatureValidator.sol
@@ -26,7 +26,6 @@ contract TestSignatureValidator is
     MixinSignatureValidator,
     MixinTransactions
 {
-
     function publicIsValidSignature(
         bytes32 hash,
         address signer,
diff --git a/packages/contracts/src/2.0.0/test/TestStaticCallReceiver/TestStaticCallReceiver.sol b/packages/contracts/src/2.0.0/test/TestStaticCallReceiver/TestStaticCallReceiver.sol
new file mode 100644
index 000000000..41aab01c8
--- /dev/null
+++ b/packages/contracts/src/2.0.0/test/TestStaticCallReceiver/TestStaticCallReceiver.sol
@@ -0,0 +1,81 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity 0.4.24;
+
+import "../../tokens/ERC20Token/IERC20Token.sol";
+
+
+// solhint-disable no-unused-vars
+contract TestStaticCallReceiver {
+
+    uint256 internal state = 1;
+
+    /// @dev Updates state and returns true. Intended to be used with `Validator` signature type.
+    /// @param hash Message hash that is signed.
+    /// @param signerAddress Address that should have signed the given hash.
+    /// @param signature Proof of signing.
+    /// @return Validity of order signature.
+    function isValidSignature(
+        bytes32 hash,
+        address signerAddress,
+        bytes signature
+    )
+        external
+        returns (bool isValid)
+    {
+        updateState();
+        return true;
+    }
+
+    /// @dev Updates state and returns true. Intended to be used with `Wallet` signature type.
+    /// @param hash Message hash that is signed.
+    /// @param signature Proof of signing.
+    /// @return Validity of order signature.
+    function isValidSignature(
+        bytes32 hash,
+        bytes signature
+    )
+        external
+        returns (bool isValid)
+    {
+        updateState();
+        return true;
+    }
+
+    /// @dev Approves an ERC20 token to spend tokens from this address.
+    /// @param token Address of ERC20 token.
+    /// @param spender Address that will spend tokens.
+    /// @param value Amount of tokens spender is approved to spend.
+    function approveERC20(
+        address token,
+        address spender,
+        uint256 value
+    )
+        external
+    {
+        IERC20Token(token).approve(spender, value);
+    }
+
+    /// @dev Increments state variable.
+    function updateState()
+        internal
+    {
+        state++;
+    }
+}
diff --git a/packages/contracts/src/2.0.0/tokens/ERC20Token/ERC20Token.sol b/packages/contracts/src/2.0.0/tokens/ERC20Token/ERC20Token.sol
index d9950145d..725d304df 100644
--- a/packages/contracts/src/2.0.0/tokens/ERC20Token/ERC20Token.sol
+++ b/packages/contracts/src/2.0.0/tokens/ERC20Token/ERC20Token.sol
@@ -21,15 +21,20 @@ pragma solidity 0.4.24;
 import "./IERC20Token.sol";
 
 
-contract ERC20Token is IERC20Token {
-
+contract ERC20Token is
+    IERC20Token
+{
     mapping (address => uint256) internal balances;
     mapping (address => mapping (address => uint256)) internal allowed;
 
-    uint256 public totalSupply;
+    uint256 internal _totalSupply;
 
+    /// @dev send `value` token to `to` from `msg.sender`
+    /// @param _to The address of the recipient
+    /// @param _value The amount of token to be transferred
+    /// @return True if transfer was successful
     function transfer(address _to, uint256 _value)
-        public
+        external
         returns (bool)
     {
         require(
@@ -38,16 +43,32 @@ contract ERC20Token is IERC20Token {
         );
         require(
             balances[_to] + _value >= balances[_to],
-            "OVERFLOW"
+            "UINT256_OVERFLOW"
         );
+
         balances[msg.sender] -= _value;
         balances[_to] += _value;
-        emit Transfer(msg.sender, _to, _value);
+
+        emit Transfer(
+            msg.sender,
+            _to,
+            _value
+        );
+
         return true;
     }
 
-    function transferFrom(address _from, address _to, uint256 _value)
-        public
+    /// @dev send `value` token to `to` from `from` on the condition it is approved by `from`
+    /// @param _from The address of the sender
+    /// @param _to The address of the recipient
+    /// @param _value The amount of token to be transferred
+    /// @return True if transfer was successful
+    function transferFrom(
+        address _from,
+        address _to,
+        uint256 _value
+    )
+        external
         returns (bool)
     {
         require(
@@ -60,34 +81,65 @@ contract ERC20Token is IERC20Token {
         );
         require(
             balances[_to] + _value >= balances[_to],
-            "OVERFLOW"
+            "UINT256_OVERFLOW"
         );
+
         balances[_to] += _value;
         balances[_from] -= _value;
         allowed[_from][msg.sender] -= _value;
-        emit Transfer(_from, _to, _value);
+    
+        emit Transfer(
+            _from,
+            _to,
+            _value
+        );
+    
         return true;
     }
 
+    /// @dev `msg.sender` approves `_spender` to spend `_value` tokens
+    /// @param _spender The address of the account able to transfer the tokens
+    /// @param _value The amount of wei to be approved for transfer
+    /// @return Always true if the call has enough gas to complete execution
     function approve(address _spender, uint256 _value)
-        public
+        external
         returns (bool)
     {
         allowed[msg.sender][_spender] = _value;
-        emit Approval(msg.sender, _spender, _value);
+        emit Approval(
+            msg.sender,
+            _spender,
+            _value
+        );
         return true;
     }
 
+    /// @dev Query total supply of token
+    /// @return Total supply of token
+    function totalSupply()
+        external
+        view
+        returns (uint256)
+    {
+        return _totalSupply;
+    }
+
+    /// @dev Query the balance of owner
+    /// @param _owner The address from which the balance will be retrieved
+    /// @return Balance of owner
     function balanceOf(address _owner)
-        public
+        external
         view
         returns (uint256)
     {
         return balances[_owner];
     }
 
+    /// @param _owner The address of the account owning tokens
+    /// @param _spender The address of the account able to transfer the tokens
+    /// @return Amount of remaining tokens allowed to spent
     function allowance(address _owner, address _spender)
-        public
+        external
         view
         returns (uint256)
     {
diff --git a/packages/contracts/src/2.0.0/tokens/ERC20Token/IERC20Token.sol b/packages/contracts/src/2.0.0/tokens/ERC20Token/IERC20Token.sol
index 5ee5e1011..258d47393 100644
--- a/packages/contracts/src/2.0.0/tokens/ERC20Token/IERC20Token.sol
+++ b/packages/contracts/src/2.0.0/tokens/ERC20Token/IERC20Token.sol
@@ -21,54 +21,67 @@ pragma solidity 0.4.24;
 
 contract IERC20Token {
 
-    /// @notice send `value` token to `to` from `msg.sender`
+    // solhint-disable no-simple-event-func-name
+    event Transfer(
+        address indexed _from,
+        address indexed _to,
+        uint256 _value
+    );
+
+    event Approval(
+        address indexed _owner,
+        address indexed _spender,
+        uint256 _value
+    );
+
+    /// @dev send `value` token to `to` from `msg.sender`
     /// @param _to The address of the recipient
     /// @param _value The amount of token to be transferred
-    /// @return Whether the transfer was successful or not
+    /// @return True if transfer was successful
     function transfer(address _to, uint256 _value)
-        public
+        external
         returns (bool);
 
-    /// @notice send `value` token to `to` from `from` on the condition it is approved by `from`
+    /// @dev send `value` token to `to` from `from` on the condition it is approved by `from`
     /// @param _from The address of the sender
     /// @param _to The address of the recipient
     /// @param _value The amount of token to be transferred
-    /// @return Whether the transfer was successful or not
-    function transferFrom(address _from, address _to, uint256 _value)
-        public
+    /// @return True if transfer was successful
+    function transferFrom(
+        address _from,
+        address _to,
+        uint256 _value
+    )
+        external
         returns (bool);
     
-    /// @notice `msg.sender` approves `_spender` to spend `_value` tokens
+    /// @dev `msg.sender` approves `_spender` to spend `_value` tokens
     /// @param _spender The address of the account able to transfer the tokens
     /// @param _value The amount of wei to be approved for transfer
-    /// @return Whether the approval was successful or not
+    /// @return Always true if the call has enough gas to complete execution
     function approve(address _spender, uint256 _value)
-        public
+        external
         returns (bool);
 
+    /// @dev Query total supply of token
+    /// @return Total supply of token
+    function totalSupply()
+        external
+        view
+        returns (uint256);
+    
     /// @param _owner The address from which the balance will be retrieved
-    /// @return The balance
+    /// @return Balance of owner
     function balanceOf(address _owner)
-        public view
+        external
+        view
         returns (uint256);
 
     /// @param _owner The address of the account owning tokens
     /// @param _spender The address of the account able to transfer the tokens
     /// @return Amount of remaining tokens allowed to spent
     function allowance(address _owner, address _spender)
-        public view
+        external
+        view
         returns (uint256);
-
-    // solhint-disable-next-line no-simple-event-func-name
-    event Transfer(
-        address indexed _from,
-        address indexed _to,
-        uint256 _value
-    );
-    
-    event Approval(
-        address indexed _owner,
-        address indexed _spender,
-        uint256 _value
-    );
 }
diff --git a/packages/contracts/src/2.0.0/tokens/ERC20Token/MintableERC20Token.sol b/packages/contracts/src/2.0.0/tokens/ERC20Token/MintableERC20Token.sol
new file mode 100644
index 000000000..9dc924422
--- /dev/null
+++ b/packages/contracts/src/2.0.0/tokens/ERC20Token/MintableERC20Token.sol
@@ -0,0 +1,60 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity 0.4.24;
+
+import "../../utils/SafeMath/SafeMath.sol";
+import "./UnlimitedAllowanceERC20Token.sol";
+
+
+contract MintableERC20Token is 
+    SafeMath,
+    UnlimitedAllowanceERC20Token
+{
+    /// @dev Mints new tokens
+    /// @param _to Address of the beneficiary that will own the minted token
+    /// @param _value Amount of tokens to mint
+    function _mint(address _to, uint256 _value)
+        internal
+    {
+        balances[_to] = safeAdd(_value, balances[_to]);
+        _totalSupply = safeAdd(_totalSupply, _value);
+
+        emit Transfer(
+            address(0),
+            _to,
+            _value
+        );
+    }
+
+    /// @dev Mints new tokens
+    /// @param _owner Owner of tokens that will be burned
+    /// @param _value Amount of tokens to burn
+    function _burn(address _owner, uint256 _value)
+        internal
+    {
+        balances[_owner] = safeSub(balances[_owner], _value);
+        _totalSupply = safeSub(_totalSupply, _value);
+
+        emit Transfer(
+            _owner,
+            address(0),
+            _value
+        );
+    }
+}
diff --git a/packages/contracts/src/2.0.0/tokens/UnlimitedAllowanceToken/UnlimitedAllowanceToken.sol b/packages/contracts/src/2.0.0/tokens/ERC20Token/UnlimitedAllowanceERC20Token.sol
index 9feb5c914..2e5bd4348 100644
--- a/packages/contracts/src/2.0.0/tokens/UnlimitedAllowanceToken/UnlimitedAllowanceToken.sol
+++ b/packages/contracts/src/2.0.0/tokens/ERC20Token/UnlimitedAllowanceERC20Token.sol
@@ -21,8 +21,9 @@ pragma solidity 0.4.24;
 import "../ERC20Token/ERC20Token.sol";
 
 
-contract UnlimitedAllowanceToken is ERC20Token {
-
+contract UnlimitedAllowanceERC20Token is
+    ERC20Token
+{
     uint256 constant internal MAX_UINT = 2**256 - 1;
 
     /// @dev ERC20 transferFrom, modified such that an allowance of MAX_UINT represents an unlimited allowance. See https://github.com/ethereum/EIPs/issues/717
@@ -30,8 +31,12 @@ contract UnlimitedAllowanceToken is ERC20Token {
     /// @param _to Address to transfer to.
     /// @param _value Amount to transfer.
     /// @return Success of transfer.
-    function transferFrom(address _from, address _to, uint256 _value)
-        public
+    function transferFrom(
+        address _from,
+        address _to,
+        uint256 _value
+    )
+        external
         returns (bool)
     {
         uint256 allowance = allowed[_from][msg.sender];
@@ -45,14 +50,21 @@ contract UnlimitedAllowanceToken is ERC20Token {
         );
         require(
             balances[_to] + _value >= balances[_to],
-            "OVERFLOW"
+            "UINT256_OVERFLOW"
         );
+
         balances[_to] += _value;
         balances[_from] -= _value;
         if (allowance < MAX_UINT) {
             allowed[_from][msg.sender] -= _value;
         }
-        emit Transfer(_from, _to, _value);
+
+        emit Transfer(
+            _from,
+            _to,
+            _value
+        );
+
         return true;
     }
 }
diff --git a/packages/contracts/src/2.0.0/tokens/ERC721Token/ERC721Token.sol b/packages/contracts/src/2.0.0/tokens/ERC721Token/ERC721Token.sol
index 60603aa19..530f080c0 100644
--- a/packages/contracts/src/2.0.0/tokens/ERC721Token/ERC721Token.sol
+++ b/packages/contracts/src/2.0.0/tokens/ERC721Token/ERC721Token.sol
@@ -1,26 +1,19 @@
 /*
-The MIT License (MIT)
 
-Copyright (c) 2016 Smart Contract Solutions, Inc.
+  Copyright 2018 ZeroEx Intl.
 
-Permission is hereby granted, free of charge, to any person obtaining
-a copy of this software and associated documentation files (the
-"Software"), to deal in the Software without restriction, including
-without limitation the rights to use, copy, modify, merge, publish,
-distribute, sublicense, and/or sell copies of the Software, and to
-permit persons to whom the Software is furnished to do so, subject to
-the following conditions:
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
 
-The above copyright notice and this permission notice shall be included
-in all copies or substantial portions of the Software.
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
 
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
-OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
-MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
-IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
-CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
-TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
-SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
 
 pragma solidity 0.4.24;
@@ -30,179 +23,250 @@ import "./IERC721Receiver.sol";
 import "../../utils/SafeMath/SafeMath.sol";
 
 
-/**
- * @title ERC721 Non-Fungible Token Standard basic implementation
- * @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
- * Modified from https://github.com/OpenZeppelin/zeppelin-solidity/blob/master/contracts/token/ERC721/ERC721BasicToken.sol
- */
 contract ERC721Token is
     IERC721Token,
     SafeMath
 {
-    // Equals to `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`
-    // which can be also obtained as `ERC721Receiver(0).onERC721Received.selector`
-    bytes4 constant internal ERC721_RECEIVED = 0xf0b9e5ba;
+    // Function selector for ERC721Receiver.onERC721Received
+    // 0x150b7a02
+    bytes4 constant internal ERC721_RECEIVED = bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"));
 
-    // Mapping from token ID to owner
-    mapping (uint256 => address) internal tokenOwner;
+    // Mapping of tokenId => owner
+    mapping (uint256 => address) internal owners;
 
-    // Mapping from token ID to approved address
-    mapping (uint256 => address) internal tokenApprovals;
+    // Mapping of tokenId => approved address
+    mapping (uint256 => address) internal approvals;
 
-    // Mapping from owner to number of owned token
-    mapping (address => uint256) internal ownedTokensCount;
+    // Mapping of owner => number of tokens owned
+    mapping (address => uint256) internal balances;
 
-    // Mapping from owner to operator approvals
+    // Mapping of owner => operator => approved
     mapping (address => mapping (address => bool)) internal operatorApprovals;
 
-    /**
-    * @dev Guarantees msg.sender is owner of the given token
-    * @param _tokenId uint256 ID of the token to validate its ownership belongs to msg.sender
-    */
-    modifier onlyOwnerOf(uint256 _tokenId) {
-        require(ownerOf(_tokenId) == msg.sender);
-        _;
-    }
-
-    /**
-    * @dev Checks msg.sender can transfer a token, by being owner, approved, or operator
-    * @param _tokenId uint256 ID of the token to validate
-    */
-    modifier canTransfer(uint256 _tokenId) {
-        require(isApprovedOrOwner(msg.sender, _tokenId));
-        _;
+    /// @notice Transfers the ownership of an NFT from one address to another address
+    /// @dev Throws unless `msg.sender` is the current owner, an authorized
+    ///      operator, or the approved address for this NFT. Throws if `_from` is
+    ///      not the current owner. Throws if `_to` is the zero address. Throws if
+    ///      `_tokenId` is not a valid NFT. When transfer is complete, this function
+    ///      checks if `_to` is a smart contract (code size > 0). If so, it calls
+    ///      `onERC721Received` on `_to` and throws if the return value is not
+    ///      `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`.
+    /// @param _from The current owner of the NFT
+    /// @param _to The new owner
+    /// @param _tokenId The NFT to transfer
+    /// @param _data Additional data with no specified format, sent in call to `_to`
+    function safeTransferFrom(
+        address _from,
+        address _to,
+        uint256 _tokenId,
+        bytes _data
+    )
+        external
+    {
+        transferFrom(
+            _from,
+            _to,
+            _tokenId
+        );
+
+        uint256 receiverCodeSize;
+        assembly {
+            receiverCodeSize := extcodesize(_to)
+        }
+        if (receiverCodeSize > 0) {
+            bytes4 selector = IERC721Receiver(_to).onERC721Received(
+                msg.sender,
+                _from,
+                _tokenId,
+                _data
+            );
+            require(
+                selector == ERC721_RECEIVED,
+                "ERC721_INVALID_SELECTOR"
+            );
+        }
     }
 
-    constructor (
-        string _name,
-        string _symbol)
-        public
+    /// @notice Transfers the ownership of an NFT from one address to another address
+    /// @dev This works identically to the other function with an extra data parameter,
+    ///      except this function just sets data to "".
+    /// @param _from The current owner of the NFT
+    /// @param _to The new owner
+    /// @param _tokenId The NFT to transfer
+    function safeTransferFrom(
+        address _from,
+        address _to,
+        uint256 _tokenId
+    )
+        external
     {
-        name_ = _name;
-        symbol_ = _symbol;
+        transferFrom(
+            _from,
+            _to,
+            _tokenId
+        );
+
+        uint256 receiverCodeSize;
+        assembly {
+            receiverCodeSize := extcodesize(_to)
+        }
+        if (receiverCodeSize > 0) {
+            bytes4 selector = IERC721Receiver(_to).onERC721Received(
+                msg.sender,
+                _from,
+                _tokenId,
+                ""
+            );
+            require(
+                selector == ERC721_RECEIVED,
+                "ERC721_INVALID_SELECTOR"
+            );
+        }
     }
 
-    /**
-    * @dev Gets the token name
-    * @return string representing the token name
-    */
-    function name()
-        public
-        view
-        returns (string)
+    /// @notice Change or reaffirm the approved address for an NFT
+    /// @dev The zero address indicates there is no approved address.
+    ///      Throws unless `msg.sender` is the current NFT owner, or an authorized
+    ///      operator of the current owner.
+    /// @param _approved The new approved NFT controller
+    /// @param _tokenId The NFT to approve
+    function approve(address _approved, uint256 _tokenId)
+        external
     {
-        return name_;
+        address owner = ownerOf(_tokenId);
+        require(
+            msg.sender == owner || isApprovedForAll(owner, msg.sender),
+            "ERC721_INVALID_SENDER"
+        );
+
+        approvals[_tokenId] = _approved;
+        emit Approval(
+            owner,
+            _approved,
+            _tokenId
+        );
     }
 
-    /**
-    * @dev Gets the token symbol
-    * @return string representing the token symbol
-    */
-    function symbol()
-        public
-        view
-        returns (string)
+    /// @notice Enable or disable approval for a third party ("operator") to manage
+    ///         all of `msg.sender`'s assets
+    /// @dev Emits the ApprovalForAll event. The contract MUST allow
+    ///      multiple operators per owner.
+    /// @param _operator Address to add to the set of authorized operators
+    /// @param _approved True if the operator is approved, false to revoke approval
+    function setApprovalForAll(address _operator, bool _approved)
+        external
     {
-        return symbol_;
+        operatorApprovals[msg.sender][_operator] = _approved;
+        emit ApprovalForAll(
+            msg.sender,
+            _operator,
+            _approved
+        );
     }
-
-    /**
-    * @dev Gets the balance of the specified address
-    * @param _owner address to query the balance of
-    * @return uint256 representing the amount owned by the passed address
-    */
+    
+    /// @notice Count all NFTs assigned to an owner
+    /// @dev NFTs assigned to the zero address are considered invalid, and this
+    ///      function throws for queries about the zero address.
+    /// @param _owner An address for whom to query the balance
+    /// @return The number of NFTs owned by `_owner`, possibly zero
     function balanceOf(address _owner)
-        public
+        external
         view
         returns (uint256)
     {
-        require(_owner != address(0));
-        return ownedTokensCount[_owner];
+        require(
+            _owner != address(0),
+            "ERC721_ZERO_OWNER"
+        );
+        return balances[_owner];
     }
 
-    /**
-    * @dev Gets the owner of the specified token ID
-    * @param _tokenId uint256 ID of the token to query the owner of
-    * @return owner address currently marked as the owner of the given token ID
-    */
-    function ownerOf(uint256 _tokenId)
-        public
-        view
-        returns (address)
-    {
-        address owner = tokenOwner[_tokenId];
-        require(owner != address(0));
-        return owner;
-    }
-
-    /**
-    * @dev Returns whether the specified token exists
-    * @param _tokenId uint256 ID of the token to query the existance of
-    * @return whether the token exists
-    */
-    function exists(uint256 _tokenId)
+    /// @notice Transfer ownership of an NFT -- THE CALLER IS RESPONSIBLE
+    ///         TO CONFIRM THAT `_to` IS CAPABLE OF RECEIVING NFTS OR ELSE
+    ///         THEY MAY BE PERMANENTLY LOST
+    /// @dev Throws unless `msg.sender` is the current owner, an authorized
+    ///      operator, or the approved address for this NFT. Throws if `_from` is
+    ///      not the current owner. Throws if `_to` is the zero address. Throws if
+    ///      `_tokenId` is not a valid NFT.
+    /// @param _from The current owner of the NFT
+    /// @param _to The new owner
+    /// @param _tokenId The NFT to transfer
+    function transferFrom(
+        address _from,
+        address _to,
+        uint256 _tokenId
+    )
         public
-        view
-        returns (bool)
     {
-        address owner = tokenOwner[_tokenId];
-        return owner != address(0);
-    }
+        require(
+            _to != address(0),
+            "ERC721_ZERO_TO_ADDRESS"
+        );
 
-    /**
-    * @dev Approves another address to transfer the given token ID
-    * @dev The zero address indicates there is no approved address.
-    * @dev There can only be one approved address per token at a given time.
-    * @dev Can only be called by the token owner or an approved operator.
-    * @param _to address to be approved for the given token ID
-    * @param _tokenId uint256 ID of the token to be approved
-    */
-    function approve(address _to, uint256 _tokenId)
-        public
-    {
         address owner = ownerOf(_tokenId);
-        require(_to != owner);
-        require(msg.sender == owner || isApprovedForAll(owner, msg.sender));
-
-        if (getApproved(_tokenId) != address(0) || _to != address(0)) {
-            tokenApprovals[_tokenId] = _to;
-            emit Approval(owner, _to, _tokenId);
+        require(
+            _from == owner,
+            "ERC721_OWNER_MISMATCH"
+        );
+
+        address spender = msg.sender;
+        address approvedAddress = getApproved(_tokenId);
+        require(
+            spender == owner ||
+            isApprovedForAll(owner, spender) ||
+            approvedAddress == spender,
+            "ERC721_INVALID_SPENDER"
+        );
+
+        if (approvedAddress != address(0)) {
+            approvals[_tokenId] = address(0);
         }
+
+        owners[_tokenId] = _to;
+        balances[_from] = safeSub(balances[_from], 1);
+        balances[_to] = safeAdd(balances[_to], 1);
+    
+        emit Transfer(
+            _from,
+            _to,
+            _tokenId
+        );
     }
 
-    /**
-    * @dev Gets the approved address for a token ID, or zero if no address set
-    * @param _tokenId uint256 ID of the token to query the approval of
-    * @return address currently approved for a the given token ID
-    */
-    function getApproved(uint256 _tokenId)
+    /// @notice Find the owner of an NFT
+    /// @dev NFTs assigned to zero address are considered invalid, and queries
+    ///      about them do throw.
+    /// @param _tokenId The identifier for an NFT
+    /// @return The address of the owner of the NFT
+    function ownerOf(uint256 _tokenId)
         public
         view
         returns (address)
     {
-        return tokenApprovals[_tokenId];
+        address owner = owners[_tokenId];
+        require(
+            owner != address(0),
+            "ERC721_ZERO_OWNER"
+        );
+        return owner;
     }
 
-    /**
-    * @dev Sets or unsets the approval of a given operator
-    * @dev An operator is allowed to transfer all tokens of the sender on their behalf
-    * @param _to operator address to set the approval
-    * @param _approved representing the status of the approval to be set
-    */
-    function setApprovalForAll(address _to, bool _approved)
+    /// @notice Get the approved address for a single NFT
+    /// @dev Throws if `_tokenId` is not a valid NFT.
+    /// @param _tokenId The NFT to find the approved address for
+    /// @return The approved address for this NFT, or the zero address if there is none
+    function getApproved(uint256 _tokenId)
         public
+        view
+        returns (address)
     {
-        require(_to != msg.sender);
-        operatorApprovals[msg.sender][_to] = _approved;
-        emit ApprovalForAll(msg.sender, _to, _approved);
+        return approvals[_tokenId];
     }
 
-    /**
-    * @dev Tells whether an operator is approved by a given owner
-    * @param _owner owner address which you want to query the approval of
-    * @param _operator operator address which you want to query the approval of
-    * @return bool whether the given operator is approved by the given owner
-    */
+    /// @notice Query if an address is an authorized operator for another address
+    /// @param _owner The address that owns the NFTs
+    /// @param _operator The address that acts on behalf of the owner
+    /// @return True if `_operator` is an approved operator for `_owner`, false otherwise
     function isApprovedForAll(address _owner, address _operator)
         public
         view
@@ -210,198 +274,4 @@ contract ERC721Token is
     {
         return operatorApprovals[_owner][_operator];
     }
-
-    /**
-    * @dev Transfers the ownership of a given token ID to another address
-    * @dev Usage of this method is discouraged, use `safeTransferFrom` whenever possible
-    * @dev Requires the msg sender to be the owner, approved, or operator
-    * @param _from current owner of the token
-    * @param _to address to receive the ownership of the given token ID
-    * @param _tokenId uint256 ID of the token to be transferred
-    */
-    function transferFrom(address _from, address _to, uint256 _tokenId)
-        public
-        canTransfer(_tokenId)
-    {
-        require(_from != address(0));
-        require(_to != address(0));
-
-        clearApproval(_from, _tokenId);
-        removeTokenFrom(_from, _tokenId);
-        addTokenTo(_to, _tokenId);
-
-        emit Transfer(_from, _to, _tokenId);
-    }
-
-    /**
-    * @dev Safely transfers the ownership of a given token ID to another address
-    * @dev If the target address is a contract, it must implement `onERC721Received`,
-    *  which is called upon a safe transfer, and return the magic value
-    *  `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`; otherwise,
-    *  the transfer is reverted.
-    * @dev Requires the msg sender to be the owner, approved, or operator
-    * @param _from current owner of the token
-    * @param _to address to receive the ownership of the given token ID
-    * @param _tokenId uint256 ID of the token to be transferred
-    */
-    function safeTransferFrom(
-        address _from,
-        address _to,
-        uint256 _tokenId)
-        public
-        canTransfer(_tokenId)
-    {
-        // solium-disable-next-line arg-overflow
-        safeTransferFrom(_from, _to, _tokenId, "");
-    }
-
-    /**
-    * @dev Safely transfers the ownership of a given token ID to another address
-    * @dev If the target address is a contract, it must implement `onERC721Received`,
-    *  which is called upon a safe transfer, and return the magic value
-    *  `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`; otherwise,
-    *  the transfer is reverted.
-    * @dev Requires the msg sender to be the owner, approved, or operator
-    * @param _from current owner of the token
-    * @param _to address to receive the ownership of the given token ID
-    * @param _tokenId uint256 ID of the token to be transferred
-    * @param _data bytes data to send along with a safe transfer check
-    */
-    function safeTransferFrom(
-        address _from,
-        address _to,
-        uint256 _tokenId,
-        bytes _data)
-        public
-        canTransfer(_tokenId)
-    {
-        transferFrom(_from, _to, _tokenId);
-        // solium-disable-next-line arg-overflow
-        require(checkAndCallSafeTransfer(_from, _to, _tokenId, _data));
-    }
-
-    /**
-    * @dev Returns whether the given spender can transfer a given token ID
-    * @param _spender address of the spender to query
-    * @param _tokenId uint256 ID of the token to be transferred
-    * @return bool whether the msg.sender is approved for the given token ID,
-    *  is an operator of the owner, or is the owner of the token
-    */
-    function isApprovedOrOwner(address _spender, uint256 _tokenId)
-        internal
-        view
-        returns (bool)
-    {
-        address owner = ownerOf(_tokenId);
-        return _spender == owner || getApproved(_tokenId) == _spender || isApprovedForAll(owner, _spender);
-    }
-
-    /**
-    * @dev Internal function to mint a new token
-    * @dev Reverts if the given token ID already exists
-    * @param _to The address that will own the minted token
-    * @param _tokenId uint256 ID of the token to be minted by the msg.sender
-    */
-    function _mint(address _to, uint256 _tokenId)
-        internal
-    {
-        require(_to != address(0));
-        addTokenTo(_to, _tokenId);
-        emit Transfer(address(0), _to, _tokenId);
-    }
-
-    /**
-    * @dev Internal function to burn a specific token
-    * @dev Reverts if the token does not exist
-    * @param _tokenId uint256 ID of the token being burned by the msg.sender
-    */
-    function _burn(address _owner, uint256 _tokenId)
-        internal
-    {
-        clearApproval(_owner, _tokenId);
-        removeTokenFrom(_owner, _tokenId);
-        emit Transfer(_owner, address(0), _tokenId);
-    }
-
-    /**
-    * @dev Internal function to clear current approval of a given token ID
-    * @dev Reverts if the given address is not indeed the owner of the token
-    * @param _owner owner of the token
-    * @param _tokenId uint256 ID of the token to be transferred
-    */
-    function clearApproval(address _owner, uint256 _tokenId)
-        internal
-    {
-        require(ownerOf(_tokenId) == _owner);
-        if (tokenApprovals[_tokenId] != address(0)) {
-            tokenApprovals[_tokenId] = address(0);
-            emit Approval(_owner, address(0), _tokenId);
-        }
-    }
-
-    /**
-    * @dev Internal function to add a token ID to the list of a given address
-    * @param _to address representing the new owner of the given token ID
-    * @param _tokenId uint256 ID of the token to be added to the tokens list of the given address
-    */
-    function addTokenTo(address _to, uint256 _tokenId)
-        internal
-    {
-        require(tokenOwner[_tokenId] == address(0));
-        tokenOwner[_tokenId] = _to;
-        ownedTokensCount[_to] = safeAdd(ownedTokensCount[_to], 1);
-    }
-
-    /**
-    * @dev Internal function to remove a token ID from the list of a given address
-    * @param _from address representing the previous owner of the given token ID
-    * @param _tokenId uint256 ID of the token to be removed from the tokens list of the given address
-    */
-    function removeTokenFrom(address _from, uint256 _tokenId)
-        internal
-    {
-        require(ownerOf(_tokenId) == _from);
-        ownedTokensCount[_from] = safeSub(ownedTokensCount[_from], 1);
-        tokenOwner[_tokenId] = address(0);
-    }
-
-    /**
-    * @dev Internal function to invoke `onERC721Received` on a target address
-    * @dev The call is not executed if the target address is not a contract
-    * @param _from address representing the previous owner of the given token ID
-    * @param _to target address that will receive the tokens
-    * @param _tokenId uint256 ID of the token to be transferred
-    * @param _data bytes optional data to send along with the call
-    * @return whether the call correctly returned the expected magic value
-    */
-    function checkAndCallSafeTransfer(
-        address _from,
-        address _to,
-        uint256 _tokenId,
-        bytes _data)
-        internal
-        returns (bool)
-    {
-        if (!isContract(_to)) {
-            return true;
-        }
-        bytes4 retval = IERC721Receiver(_to).onERC721Received(_from, _tokenId, _data);
-        return (retval == ERC721_RECEIVED);
-    }
-
-    function isContract(address addr)
-        internal
-        view
-        returns (bool)
-    {
-        uint256 size;
-        // XXX Currently there is no better way to check if there is a contract in an address
-        // than to check the size of the code at that address.
-        // See https://ethereum.stackexchange.com/a/14016/36603
-        // for more details about how this works.
-        // TODO Check this again before the Serenity release, because all addresses will be
-        // contracts then.
-        assembly { size := extcodesize(addr) }  // solium-disable-line security/no-inline-assembly
-        return size > 0;
-    }
 }
diff --git a/packages/contracts/src/2.0.0/tokens/ERC721Token/IERC721Receiver.sol b/packages/contracts/src/2.0.0/tokens/ERC721Token/IERC721Receiver.sol
index f2e8f3c88..8e0e32ab2 100644
--- a/packages/contracts/src/2.0.0/tokens/ERC721Token/IERC721Receiver.sol
+++ b/packages/contracts/src/2.0.0/tokens/ERC721Token/IERC721Receiver.sol
@@ -1,61 +1,44 @@
 /*
-The MIT License (MIT)
-
-Copyright (c) 2016 Smart Contract Solutions, Inc.
-
-Permission is hereby granted, free of charge, to any person obtaining
-a copy of this software and associated documentation files (the
-"Software"), to deal in the Software without restriction, including
-without limitation the rights to use, copy, modify, merge, publish,
-distribute, sublicense, and/or sell copies of the Software, and to
-permit persons to whom the Software is furnished to do so, subject to
-the following conditions:
-
-The above copyright notice and this permission notice shall be included
-in all copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
-OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
-MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
-IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
-CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
-TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
-SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
 */
 
 pragma solidity 0.4.24;
 
 
-/**
- * @title ERC721 token receiver interface
- * @dev Interface for any contract that wants to support safeTransfers
- *      rom ERC721 asset contracts.
- * Modified from https://github.com/OpenZeppelin/zeppelin-solidity/blob/master/contracts/token/ERC721/ERC721Receiver.sol
- */
 contract IERC721Receiver {
-    /**
-    * @dev Magic value to be returned upon successful reception of an NFT
-    *  Equals to `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`,
-    *  which can be also obtained as `ERC721Receiver(0).onERC721Received.selector`
-    */
-    bytes4 constant internal ERC721_RECEIVED = 0xf0b9e5ba;
-
-    /**
-    * @notice Handle the receipt of an NFT
-    * @dev The ERC721 smart contract calls this function on the recipient
-    *  after a `safetransfer`. This function MAY throw to revert and reject the
-    *  transfer. This function MUST use 50,000 gas or less. Return of other
-    *  than the magic value MUST result in the transaction being reverted.
-    *  Note: the contract address is always the message sender.
-    * @param _from The sending address
-    * @param _tokenId The NFT identifier which is being transfered
-    * @param _data Additional data with no specified format
-    * @return `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`
-    */
+
+    /// @notice Handle the receipt of an NFT
+    /// @dev The ERC721 smart contract calls this function on the recipient
+    ///  after a `transfer`. This function MAY throw to revert and reject the
+    ///  transfer. Return of other than the magic value MUST result in the
+    ///  transaction being reverted.
+    ///  Note: the contract address is always the message sender.
+    /// @param _operator The address which called `safeTransferFrom` function
+    /// @param _from The address which previously owned the token
+    /// @param _tokenId The NFT identifier which is being transferred
+    /// @param _data Additional data with no specified format
+    /// @return `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
+    ///  unless throwing
     function onERC721Received(
+        address _operator,
         address _from,
         uint256 _tokenId,
-        bytes _data)
-        public
+        bytes _data
+    )
+        external
         returns (bytes4);
 }
diff --git a/packages/contracts/src/2.0.0/tokens/ERC721Token/IERC721Token.sol b/packages/contracts/src/2.0.0/tokens/ERC721Token/IERC721Token.sol
index 4d57ece38..ac992c80d 100644
--- a/packages/contracts/src/2.0.0/tokens/ERC721Token/IERC721Token.sol
+++ b/packages/contracts/src/2.0.0/tokens/ERC721Token/IERC721Token.sol
@@ -1,118 +1,158 @@
 /*
-The MIT License (MIT)
-
-Copyright (c) 2016 Smart Contract Solutions, Inc.
-
-Permission is hereby granted, free of charge, to any person obtaining
-a copy of this software and associated documentation files (the
-"Software"), to deal in the Software without restriction, including
-without limitation the rights to use, copy, modify, merge, publish,
-distribute, sublicense, and/or sell copies of the Software, and to
-permit persons to whom the Software is furnished to do so, subject to
-the following conditions:
-
-The above copyright notice and this permission notice shall be included
-in all copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
-OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
-MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
-IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
-CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
-TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
-SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
 */
 
 pragma solidity 0.4.24;
 
 
-/**
- * @title ERC721 Non-Fungible Token Standard basic interface
- * @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
- * Modified from https://github.com/OpenZeppelin/zeppelin-solidity/blob/master/contracts/token/ERC721/ERC721Basic.sol
- */
 contract IERC721Token {
-    string internal name_;
-    string internal symbol_;
 
+    /// @dev This emits when ownership of any NFT changes by any mechanism.
+    ///      This event emits when NFTs are created (`from` == 0) and destroyed
+    ///      (`to` == 0). Exception: during contract creation, any number of NFTs
+    ///      may be created and assigned without emitting Transfer. At the time of
+    ///      any transfer, the approved address for that NFT (if any) is reset to none.
     event Transfer(
         address indexed _from,
         address indexed _to,
-        uint256 _tokenId
+        uint256 indexed _tokenId
     );
 
+    /// @dev This emits when the approved address for an NFT is changed or
+    ///      reaffirmed. The zero address indicates there is no approved address.
+    ///      When a Transfer event emits, this also indicates that the approved
+    ///      address for that NFT (if any) is reset to none.
     event Approval(
         address indexed _owner,
         address indexed _approved,
-        uint256 _tokenId
+        uint256 indexed _tokenId
     );
 
+    /// @dev This emits when an operator is enabled or disabled for an owner.
+    ///      The operator can manage all NFTs of the owner.
     event ApprovalForAll(
         address indexed _owner,
         address indexed _operator,
         bool _approved
     );
 
-    function name()
-        public
-        view
-        returns (string);
-
-    function symbol()
-        public
-        view
-        returns (string);
+    /// @notice Transfers the ownership of an NFT from one address to another address
+    /// @dev Throws unless `msg.sender` is the current owner, an authorized
+    ///      perator, or the approved address for this NFT. Throws if `_from` is
+    ///      not the current owner. Throws if `_to` is the zero address. Throws if
+    ///      `_tokenId` is not a valid NFT. When transfer is complete, this function
+    ///      checks if `_to` is a smart contract (code size > 0). If so, it calls
+    ///      `onERC721Received` on `_to` and throws if the return value is not
+    ///      `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`.
+    /// @param _from The current owner of the NFT
+    /// @param _to The new owner
+    /// @param _tokenId The NFT to transfer
+    /// @param _data Additional data with no specified format, sent in call to `_to`
+    function safeTransferFrom(
+        address _from,
+        address _to,
+        uint256 _tokenId,
+        bytes _data
+    )
+        external;
+
+    /// @notice Transfers the ownership of an NFT from one address to another address
+    /// @dev This works identically to the other function with an extra data parameter,
+    ///      except this function just sets data to "".
+    /// @param _from The current owner of the NFT
+    /// @param _to The new owner
+    /// @param _tokenId The NFT to transfer
+    function safeTransferFrom(
+        address _from,
+        address _to,
+        uint256 _tokenId
+    )
+        external;
+
+    /// @notice Change or reaffirm the approved address for an NFT
+    /// @dev The zero address indicates there is no approved address.
+    ///      Throws unless `msg.sender` is the current NFT owner, or an authorized
+    ///      operator of the current owner.
+    /// @param _approved The new approved NFT controller
+    /// @param _tokenId The NFT to approve
+    function approve(address _approved, uint256 _tokenId)
+        external;
+
+    /// @notice Enable or disable approval for a third party ("operator") to manage
+    ///         all of `msg.sender`'s assets
+    /// @dev Emits the ApprovalForAll event. The contract MUST allow
+    ///      multiple operators per owner.
+    /// @param _operator Address to add to the set of authorized operators
+    /// @param _approved True if the operator is approved, false to revoke approval
+    function setApprovalForAll(address _operator, bool _approved)
+        external;
 
+    /// @notice Count all NFTs assigned to an owner
+    /// @dev NFTs assigned to the zero address are considered invalid, and this
+    ///      function throws for queries about the zero address.
+    /// @param _owner An address for whom to query the balance
+    /// @return The number of NFTs owned by `_owner`, possibly zero
     function balanceOf(address _owner)
-        public
+        external
         view
-        returns (uint256 _balance);
+        returns (uint256);
+
+    /// @notice Transfer ownership of an NFT -- THE CALLER IS RESPONSIBLE
+    ///         TO CONFIRM THAT `_to` IS CAPABLE OF RECEIVING NFTS OR ELSE
+    ///         THEY MAY BE PERMANENTLY LOST
+    /// @dev Throws unless `msg.sender` is the current owner, an authorized
+    ///      operator, or the approved address for this NFT. Throws if `_from` is
+    ///      not the current owner. Throws if `_to` is the zero address. Throws if
+    ///      `_tokenId` is not a valid NFT.
+    /// @param _from The current owner of the NFT
+    /// @param _to The new owner
+    /// @param _tokenId The NFT to transfer
+    function transferFrom(
+        address _from,
+        address _to,
+        uint256 _tokenId
+    )
+        public;
 
+    /// @notice Find the owner of an NFT
+    /// @dev NFTs assigned to zero address are considered invalid, and queries
+    ///      about them do throw.
+    /// @param _tokenId The identifier for an NFT
+    /// @return The address of the owner of the NFT
     function ownerOf(uint256 _tokenId)
         public
         view
-        returns (address _owner);
+        returns (address);
 
-    function exists(uint256 _tokenId)
+    /// @notice Get the approved address for a single NFT
+    /// @dev Throws if `_tokenId` is not a valid NFT.
+    /// @param _tokenId The NFT to find the approved address for
+    /// @return The approved address for this NFT, or the zero address if there is none
+    function getApproved(uint256 _tokenId) 
         public
         view
-        returns (bool _exists);
-
-    function approve(address _to, uint256 _tokenId)
-        public;
-
-    function getApproved(uint256 _tokenId)
-        public
-        view
-        returns (address _operator);
-
-    function setApprovalForAll(address _operator, bool _approved)
-        public;
-
+        returns (address);
+    
+    /// @notice Query if an address is an authorized operator for another address
+    /// @param _owner The address that owns the NFTs
+    /// @param _operator The address that acts on behalf of the owner
+    /// @return True if `_operator` is an approved operator for `_owner`, false otherwise
     function isApprovedForAll(address _owner, address _operator)
         public
         view
         returns (bool);
-
-    function transferFrom(
-        address _from,
-        address _to,
-        uint256 _tokenId
-    )
-        public;
-
-    function safeTransferFrom(
-        address _from,
-        address _to,
-        uint256 _tokenId
-    )
-        public;
-
-    function safeTransferFrom(
-        address _from,
-        address _to,
-        uint256 _tokenId,
-        bytes _data
-    )
-        public;
 }
diff --git a/packages/contracts/src/2.0.0/tokens/ERC721Token/MintableERC721Token.sol b/packages/contracts/src/2.0.0/tokens/ERC721Token/MintableERC721Token.sol
new file mode 100644
index 000000000..bc5cd2cc2
--- /dev/null
+++ b/packages/contracts/src/2.0.0/tokens/ERC721Token/MintableERC721Token.sol
@@ -0,0 +1,82 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity 0.4.24;
+
+import "./ERC721Token.sol";
+
+
+contract MintableERC721Token is
+    ERC721Token
+{
+    /// @dev Function to mint a new token
+    ///      Reverts if the given token ID already exists
+    /// @param _to Address of the beneficiary that will own the minted token
+    /// @param _tokenId ID of the token to be minted by the msg.sender    
+    function _mint(address _to, uint256 _tokenId)
+        internal
+    {
+        require(
+            _to != address(0),
+            "ERC721_ZERO_TO_ADDRESS"
+        );
+
+        address owner = owners[_tokenId];
+        require(
+            owner == address(0),
+            "ERC721_OWNER_ALREADY_EXISTS"
+        );
+
+        owners[_tokenId] = _to;
+        balances[_to] = safeAdd(balances[_to], 1);
+
+        emit Transfer(
+            address(0),
+            _to,
+            _tokenId
+        );
+    }
+
+    /// @dev Function to burn a token
+    ///      Reverts if the given token ID doesn't exist
+    /// @param _owner Owner of token with given token ID
+    /// @param _tokenId ID of the token to be burned by the msg.sender
+    function _burn(address _owner, uint256 _tokenId)
+        internal
+    {
+        require(
+            _owner != address(0),
+            "ERC721_ZERO_OWNER_ADDRESS"
+        );
+
+        address owner = owners[_tokenId];
+        require(
+            owner == _owner,
+            "ERC721_OWNER_MISMATCH"
+        );
+
+        owners[_tokenId] = address(0);
+        balances[_owner] = safeSub(balances[_owner], 1);
+
+        emit Transfer(
+            _owner,
+            address(0),
+            _tokenId
+        );
+    }
+}
diff --git a/packages/contracts/src/2.0.0/tokens/ZRXToken/ZRXToken.sol b/packages/contracts/src/2.0.0/tokens/ZRXToken/ZRXToken.sol
index 28c0b2fb3..f4855759c 100644
--- a/packages/contracts/src/2.0.0/tokens/ZRXToken/ZRXToken.sol
+++ b/packages/contracts/src/2.0.0/tokens/ZRXToken/ZRXToken.sol
@@ -22,11 +22,13 @@ pragma solidity 0.4.11;
 import { UnlimitedAllowanceToken_v1 as UnlimitedAllowanceToken } from "../../../1.0.0/UnlimitedAllowanceToken/UnlimitedAllowanceToken_v1.sol";
 
 
-contract ZRXToken is UnlimitedAllowanceToken {
+contract ZRXToken is 
+    UnlimitedAllowanceToken
+{
 
     // solhint-disable const-name-snakecase
     uint8 constant public decimals = 18;
-    uint public totalSupply = 10**27; // 1 billion tokens, 18 decimal places
+    uint256 public totalSupply = 10**27; // 1 billion tokens, 18 decimal places
     string constant public name = "0x Protocol Token";
     string constant public symbol = "ZRX";
     // solhint-enableconst-name-snakecase
diff --git a/packages/contracts/src/2.0.0/utils/LibBytes/LibBytes.sol b/packages/contracts/src/2.0.0/utils/LibBytes/LibBytes.sol
index 504e950a8..369f588ad 100644
--- a/packages/contracts/src/2.0.0/utils/LibBytes/LibBytes.sol
+++ b/packages/contracts/src/2.0.0/utils/LibBytes/LibBytes.sol
@@ -188,7 +188,8 @@ library LibBytes {
         memCopy(
             result.contentAddress(),
             b.contentAddress() + from,
-            result.length);
+            result.length
+        );
         return result;
     }
     
@@ -433,7 +434,8 @@ library LibBytes {
         pure
         returns (uint256 result)
     {
-        return uint256(readBytes32(b, index));
+        result = uint256(readBytes32(b, index));
+        return result;
     }
 
     /// @dev Writes a uint256 into a specific position in a byte array.
@@ -467,8 +469,13 @@ library LibBytes {
             b.length >= index + 4,
             "GREATER_OR_EQUAL_TO_4_LENGTH_REQUIRED"
         );
+
+        // Arrays are prefixed by a 32 byte length field
+        index += 32;
+
+        // Read the bytes4 from array memory
         assembly {
-            result := mload(add(b, 32))
+            result := mload(add(b, index))
             // Solidity does not require us to clean the trailing bytes.
             // We do it anyway
             result := and(result, 0xFFFFFFFF00000000000000000000000000000000000000000000000000000000)
diff --git a/packages/contracts/src/2.0.0/utils/Ownable/IOwnable.sol b/packages/contracts/src/2.0.0/utils/Ownable/IOwnable.sol
index 116b8dc89..5deb13497 100644
--- a/packages/contracts/src/2.0.0/utils/Ownable/IOwnable.sol
+++ b/packages/contracts/src/2.0.0/utils/Ownable/IOwnable.sol
@@ -1,13 +1,8 @@
 pragma solidity 0.4.24;
 
-/*
- * Ownable
- *
- * Base contract with an owner.
- * Provides onlyOwner modifier, which prevents function from running if it is called by anyone other than the owner.
- */
 
 contract IOwnable {
+
     function transferOwnership(address newOwner)
         public;
 }
diff --git a/packages/contracts/src/2.0.0/utils/Ownable/Ownable.sol b/packages/contracts/src/2.0.0/utils/Ownable/Ownable.sol
index aca65aad2..0c830be68 100644
--- a/packages/contracts/src/2.0.0/utils/Ownable/Ownable.sol
+++ b/packages/contracts/src/2.0.0/utils/Ownable/Ownable.sol
@@ -1,16 +1,11 @@
 pragma solidity 0.4.24;
 
-/*
- * Ownable
- *
- * Base contract with an owner.
- * Provides onlyOwner modifier, which prevents function from running if it is called by anyone other than the owner.
- */
-
 import "./IOwnable.sol";
 
 
-contract Ownable is IOwnable {
+contract Ownable is
+    IOwnable
+{
     address public owner;
 
     constructor ()
diff --git a/packages/contracts/src/2.0.0/test/Mintable/Mintable.sol b/packages/contracts/src/2.0.0/utils/ReentrancyGuard/ReentrancyGuard.sol
index 767cc8d25..9f98a7a16 100644
--- a/packages/contracts/src/2.0.0/test/Mintable/Mintable.sol
+++ b/packages/contracts/src/2.0.0/utils/ReentrancyGuard/ReentrancyGuard.sol
@@ -18,26 +18,28 @@
 
 pragma solidity 0.4.24;
 
-import "../../tokens/UnlimitedAllowanceToken/UnlimitedAllowanceToken.sol";
-import "../../utils/SafeMath/SafeMath.sol";
 
+contract ReentrancyGuard {
 
-/*
- * Mintable
- * Base contract that creates a mintable UnlimitedAllowanceToken
- */
-contract Mintable is 
-    UnlimitedAllowanceToken,
-    SafeMath
-{
-    function mint(uint256 _value)
-        public
-    {
+    // Locked state of mutex
+    bool private locked = false;
+
+    /// @dev Functions with this modifer cannot be reentered. The mutex will be locked
+    ///      before function execution and unlocked after.
+    modifier nonReentrant() {
+        // Ensure mutex is unlocked
         require(
-            _value <= 100000000000000000000,
-            "Minting more than 100000000000000000000 is not allowed."
+            !locked,
+            "REENTRANCY_ILLEGAL"
         );
-        balances[msg.sender] = safeAdd(_value, balances[msg.sender]);
-        totalSupply = safeAdd(totalSupply, _value);
+
+        // Lock mutex before function call
+        locked = true;
+
+        // Perform function call
+        _;
+
+        // Unlock mutex after function call
+        locked = false;
     }
 }
diff --git a/packages/contracts/src/2.0.0/utils/SafeMath/SafeMath.sol b/packages/contracts/src/2.0.0/utils/SafeMath/SafeMath.sol
index 63a2a085f..2855edb9d 100644
--- a/packages/contracts/src/2.0.0/utils/SafeMath/SafeMath.sol
+++ b/packages/contracts/src/2.0.0/utils/SafeMath/SafeMath.sol
@@ -2,6 +2,7 @@ pragma solidity 0.4.24;
 
 
 contract SafeMath {
+
     function safeMul(uint256 a, uint256 b)
         internal
         pure