Merge pull request #546 from 0xProject/feature/contracts/solidity-0.4.23

Use Solidity 0.4.23 

50 files changed, 1112 insertions, 674 deletions

diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/proxies/ERC20Proxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC20Proxy.sol
index 713e8a6e6..c02536d67 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/proxies/ERC20Proxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC20Proxy.sol
@@ -16,21 +16,28 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
 pragma experimental ABIEncoderV2;
 
-
-import "../../../utils/LibBytes/LibBytes.sol";
-import "../../../tokens/ERC20Token/IERC20Token.sol";
-import "../MixinAssetProxy.sol";
+import "../../utils/LibBytes/LibBytes.sol";
+import "../../tokens/ERC20Token/IERC20Token.sol";
+import "./MixinAssetProxy.sol";
+import "./MixinAuthorizable.sol";
 
 contract ERC20Proxy is
     LibBytes,
-    MixinAssetProxy
+    MixinAssetProxy,
+    MixinAuthorizable
 {
 
+    // Id of this proxy.
     uint8 constant PROXY_ID = 1;
 
+    // Revert reasons
+    string constant INVALID_METADATA_LENGTH = "Metadata must have a length of 21.";
+    string constant TRANSFER_FAILED = "Transfer failed.";
+    string constant PROXY_ID_MISMATCH = "Proxy id in metadata does not match this proxy id.";
+
     /// @dev Internal version of `transferFrom`.
     /// @param assetMetadata Encoded byte array.
     /// @param from Address to transfer asset from.
@@ -44,15 +51,24 @@ contract ERC20Proxy is
         internal
     {
         // Data must be intended for this proxy.
-        require(uint8(assetMetadata[0]) == PROXY_ID);
+        require(
+            uint8(assetMetadata[0]) == PROXY_ID,
+            PROXY_ID_MISMATCH
+        );
 
         // Decode metadata.
-        require(assetMetadata.length == 21);
+        require(
+            assetMetadata.length == 21,
+            INVALID_METADATA_LENGTH
+        );
         address token = readAddress(assetMetadata, 1);
 
         // Transfer tokens.
         bool success = IERC20Token(token).transferFrom(from, to, amount);
-        require(success == true);
+        require(
+            success == true,
+            TRANSFER_FAILED
+        );
     }
 
     /// @dev Gets the proxy id associated with the proxy address.
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/proxies/ERC721Proxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC721Proxy.sol
index 6a4475d48..475359087 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/proxies/ERC721Proxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC721Proxy.sol
@@ -16,20 +16,28 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
 pragma experimental ABIEncoderV2;
 
-import "../../../utils/LibBytes/LibBytes.sol";
-import "../../../tokens/ERC721Token/ERC721Token.sol";
-import "../MixinAssetProxy.sol";
+import "../../utils/LibBytes/LibBytes.sol";
+import "../../tokens/ERC721Token/ERC721Token.sol";
+import "./MixinAssetProxy.sol";
+import "./MixinAuthorizable.sol";
 
 contract ERC721Proxy is
     LibBytes,
-    MixinAssetProxy
+    MixinAssetProxy,
+    MixinAuthorizable
 {
 
+    // Id of this proxy.
     uint8 constant PROXY_ID = 2;
 
+    // Revert reasons
+    string constant INVALID_TRANSFER_AMOUNT = "Transfer amount must equal 1.";
+    string constant INVALID_METADATA_LENGTH = "Metadata must have a length of 53.";
+    string constant PROXY_ID_MISMATCH = "Proxy id in metadata does not match this proxy id.";
+
     /// @dev Internal version of `transferFrom`.
     /// @param assetMetadata Encoded byte array.
     /// @param from Address to transfer asset from.
@@ -43,13 +51,22 @@ contract ERC721Proxy is
         internal
     {
         // Data must be intended for this proxy.
-        require(uint8(assetMetadata[0]) == PROXY_ID);
+        require(
+            uint8(assetMetadata[0]) == PROXY_ID,
+            PROXY_ID_MISMATCH
+        );
 
         // There exists only 1 of each token.
-        require(amount == 1);
+        require(
+            amount == 1,
+            INVALID_TRANSFER_AMOUNT
+        );
 
-        // Decode metadata.
-        require(assetMetadata.length == 53);
+        // Decode metadata
+        require(
+            assetMetadata.length == 53,
+            INVALID_METADATA_LENGTH
+        );
         address token = readAddress(assetMetadata, 1);
         uint256 tokenId = readUint256(assetMetadata, 21);
 
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAssetProxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAssetProxy.sol
index 23dce6a8b..d58cfc2dd 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAssetProxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAssetProxy.sol
@@ -16,17 +16,15 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
 pragma experimental ABIEncoderV2;
 
 import "./mixins/MAssetProxy.sol";
-import "./IAssetProxy.sol";
-import "../../utils/Authorizable/Authorizable.sol";
+import "./mixins/MAuthorizable.sol";
 
 contract MixinAssetProxy is 
-    IAssetProxy,
-    MAssetProxy,
-    Authorizable
+    MAuthorizable,
+    MAssetProxy
 {
 
     /// @dev Transfers assets. Either succeeds or throws.
diff --git a/packages/contracts/src/contracts/current/utils/Authorizable/Authorizable.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAuthorizable.sol
index f6032f889..b66b783ea 100644
--- a/packages/contracts/src/contracts/current/utils/Authorizable/Authorizable.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAuthorizable.sol
@@ -16,46 +16,47 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
+pragma experimental ABIEncoderV2;
 
-import "./IAuthorizable.sol";
-import "../Ownable/Ownable.sol";
+import "./mixins/MAuthorizable.sol";
+import "../../utils/Ownable/Ownable.sol";
 
-contract Authorizable is
+contract MixinAuthorizable is
     Ownable,
-    IAuthorizable
+    MAuthorizable
 {
 
+    // Revert reasons
+    string constant SENDER_NOT_AUTHORIZED = "Sender not authorized to call this method.";
+    string constant TARGET_NOT_AUTHORIZED = "Target address must be authorized.";
+    string constant TARGET_ALREADY_AUTHORIZED = "Target must not already be authorized.";
+    string constant INDEX_OUT_OF_BOUNDS = "Specified array index is out of bounds.";
+    string constant INDEX_ADDRESS_MISMATCH = "Address found at index does not match target address.";
+
     /// @dev Only authorized addresses can invoke functions with this modifier.
     modifier onlyAuthorized {
-        require(authorized[msg.sender]);
-        _;
-    }
-
-    modifier targetAuthorized(address target) {
-        require(authorized[target]);
-        _;
-    }
-
-    modifier targetNotAuthorized(address target) {
-        require(!authorized[target]);
+        require(
+            authorized[msg.sender],
+            SENDER_NOT_AUTHORIZED
+        );
         _;
     }
 
     mapping (address => bool) public authorized;
     address[] public authorities;
 
-    /*
-     * Public functions
-     */
-
     /// @dev Authorizes an address.
     /// @param target Address to authorize.
     function addAuthorizedAddress(address target)
-        public
+        external
         onlyOwner
-        targetNotAuthorized(target)
     {
+        require(
+            !authorized[target],
+            TARGET_ALREADY_AUTHORIZED
+        );
+
         authorized[target] = true;
         authorities.push(target);
         emit AuthorizedAddressAdded(target, msg.sender);
@@ -64,10 +65,14 @@ contract Authorizable is
     /// @dev Removes authorizion of an address.
     /// @param target Address to remove authorization from.
     function removeAuthorizedAddress(address target)
-        public
+        external
         onlyOwner
-        targetAuthorized(target)
     {
+        require(
+            authorized[target],
+            TARGET_NOT_AUTHORIZED
+        );
+
         delete authorized[target];
         for (uint i = 0; i < authorities.length; i++) {
             if (authorities[i] == target) {
@@ -83,24 +88,28 @@ contract Authorizable is
     /// @param target Address to remove authorization from.
     /// @param index Index of target in authorities array.
     function removeAuthorizedAddressAtIndex(address target, uint256 index)
-        public
+        external
     {
-        require(index < authorities.length);
-        require(authorities[index] == target);
+        require(
+            index < authorities.length,
+            INDEX_OUT_OF_BOUNDS
+        );
+        require(
+            authorities[index] == target,
+            INDEX_ADDRESS_MISMATCH
+        );
+
         delete authorized[target];
         authorities[index] = authorities[authorities.length - 1];
         authorities.length -= 1;
         emit AuthorizedAddressRemoved(target, msg.sender);
     }
 
-    /*
-     * Public constant functions
-     */
-
     /// @dev Gets all authorized addresses.
     /// @return Array of authorized addresses.
     function getAuthorizedAddresses()
-        public view
+        external
+        view
         returns (address[] memory)
     {
         return authorities;
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/IAssetProxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAssetProxy.sol
index df993a0ab..eca6524e5 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/IAssetProxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAssetProxy.sol
@@ -16,12 +16,14 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
 pragma experimental ABIEncoderV2;
 
-import "../../utils/Authorizable/IAuthorizable.sol";
+import "./IAuthorizable.sol";
 
-contract IAssetProxy is IAuthorizable {
+contract IAssetProxy is
+    IAuthorizable
+{
 
     /// @dev Transfers assets. Either succeeds or throws.
     /// @param assetMetadata Byte array encoded for the respective asset proxy.
diff --git a/packages/contracts/src/contracts/current/utils/Authorizable/IAuthorizable.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAuthorizable.sol
index 10c01c6fe..3120be7ec 100644
--- a/packages/contracts/src/contracts/current/utils/Authorizable/IAuthorizable.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAuthorizable.sol
@@ -16,37 +16,35 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
+pragma experimental ABIEncoderV2;
 
-contract IAuthorizable {
+import "../../../utils/Ownable/IOwnable.sol";
+
+contract IAuthorizable is
+    IOwnable
+{
 
     /// @dev Gets all authorized addresses.
     /// @return Array of authorized addresses.
     function getAuthorizedAddresses()
-        public view
+        external
+        view
         returns (address[]);
 
     /// @dev Authorizes an address.
     /// @param target Address to authorize.
     function addAuthorizedAddress(address target)
-        public;
+        external;
 
     /// @dev Removes authorizion of an address.
     /// @param target Address to remove authorization from.
     function removeAuthorizedAddress(address target)
-        public;
+        external;
 
     /// @dev Removes authorizion of an address.
     /// @param target Address to remove authorization from.
     /// @param index Index of target in authorities array.
     function removeAuthorizedAddressAtIndex(address target, uint256 index)
-        public;
-
-    event AuthorizedAddressAdded(
-        address indexed target,
-        address indexed caller);
-
-    event AuthorizedAddressRemoved(
-        address indexed target,
-        address indexed caller);
+        external;
 }
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAssetProxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAssetProxy.sol
index 8e9b3bc65..e0ec8c4e1 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAssetProxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAssetProxy.sol
@@ -16,10 +16,14 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
 pragma experimental ABIEncoderV2;
 
-contract MAssetProxy {
+import "../interfaces/IAssetProxy.sol";
+
+contract MAssetProxy is
+    IAssetProxy
+{
 
     /// @dev Internal version of `transferFrom`.
     /// @param assetMetadata Encoded byte array.
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/LibErrors.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAuthorizable.sol
index 55160ad5b..71d1910e5 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/LibErrors.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAuthorizable.sol
@@ -16,20 +16,27 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
 pragma experimental ABIEncoderV2;
 
-contract LibErrors {
+import "../interfaces/IAuthorizable.sol";
 
-    // Error Codes
-    enum Errors {
-        ORDER_EXPIRED,                    // Order has already expired
-        ORDER_FULLY_FILLED,               // Order has already been fully filled
-        ORDER_CANCELLED,                  // Order has already been cancelled
-        ROUNDING_ERROR_TOO_LARGE,         // Rounding error too large
-        INSUFFICIENT_BALANCE_OR_ALLOWANCE // Insufficient balance or allowance for token transfer
-    }
+contract MAuthorizable is
+    IAuthorizable
+{
 
-    event ExchangeError(uint8 indexed errorId, bytes32 indexed orderHash);
+    // Event logged when a new address is authorized.
+    event AuthorizedAddressAdded(
+        address indexed target,
+        address indexed caller
+    );
 
+    // Event logged when a currently authorized address is unauthorized.
+    event AuthorizedAddressRemoved(
+        address indexed target,
+        address indexed caller
+    );
+
+    /// @dev Only authorized addresses can invoke functions with this modifier.
+    modifier onlyAuthorized { _; }
 }
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/Exchange.sol b/packages/contracts/src/contracts/current/protocol/Exchange/Exchange.sol
index e78446b99..85e2bc47e 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/Exchange.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/Exchange.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
 pragma experimental ABIEncoderV2;
 
 import "./MixinExchangeCore.sol";
@@ -36,7 +36,7 @@ contract Exchange is
 {
     string constant public VERSION = "2.0.1-alpha";
 
-    function Exchange(bytes memory _zrxProxyData)
+    constructor (bytes memory _zrxProxyData)
         public
         MixinExchangeCore()
         MixinSignatureValidator()
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/IExchange.sol b/packages/contracts/src/contracts/current/protocol/Exchange/IExchange.sol
deleted file mode 100644
index ef2fb2a96..000000000
--- a/packages/contracts/src/contracts/current/protocol/Exchange/IExchange.sol
+++ /dev/null
@@ -1,289 +0,0 @@
-/*
-
-  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 ^0.4.21;
-pragma experimental ABIEncoderV2;
-
-contract IExchange {
-
-    // Error Codes
-    enum Errors {
-        ORDER_EXPIRED,                    // Order has already expired
-        ORDER_FULLY_FILLED_OR_CANCELLED,  // Order has already been fully filled or cancelled
-        ROUNDING_ERROR_TOO_LARGE,         // Rounding error too large
-        INSUFFICIENT_BALANCE_OR_ALLOWANCE // Insufficient balance or allowance for token transfer
-    }
-
-    event LogError(uint8 indexed errorId, bytes32 indexed orderHash);
-
-    event LogFill(
-        address indexed maker,
-        address taker,
-        address indexed feeRecipient,
-        bytes makerAssetData,
-        bytes takerAssetData,
-        uint256 makerAssetFilledAmount,
-        uint256 takerAssetFilledAmount,
-        uint256 makerFeePaid,
-        uint256 takerFeePaid,
-        bytes32 indexed orderHash
-    );
-
-    event LogCancel(
-        address indexed maker,
-        address indexed feeRecipient,
-        bytes makerAssetData,
-        bytes takerAssetData,
-        uint256 makerAssetCancelledAmount,
-        uint256 takerAssetCancelledAmount,
-        bytes32 indexed orderHash
-    );
-
-    function ZRX_TOKEN_CONTRACT()
-      public view
-      returns (address);
-
-    function EXTERNAL_QUERY_GAS_LIMIT()
-      public view
-      returns (uint16);
-
-    function VERSION()
-      public view
-      returns (string);
-
-    function filled(bytes32)
-      public view
-      returns (uint256);
-
-    function cancelled(bytes32)
-      public view
-      returns (uint256);
-
-    /// @dev Calculates the sum of values already filled and cancelled for a given order.
-    /// @param orderHash The Keccak-256 hash of the given order.
-    /// @return Sum of values already filled and cancelled.
-    function getUnavailableTakerAssetAmount(bytes32 orderHash)
-        public view
-        returns (uint256 unavailableTakerAssetAmount);
-
-    /// @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 getPartialAmount(uint256 numerator, uint256 denominator, uint256 target)
-        public pure
-        returns (uint256 partialAmount);
-
-    /// @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 isRoundingError(uint256 numerator, uint256 denominator, uint256 target)
-        public pure
-        returns (bool isError);
-
-    /// @dev Calculates Keccak-256 hash of order with specified parameters.
-    /// @param orderAddresses Array of order's maker, taker, makerAsset, takerAsset, and feeRecipient.
-    /// @param orderValues Array of order's makerAssetAmount, takerAssetAmount, makerFee, takerFee, expirationTimestampInSec, and salt.
-    /// @return Keccak-256 hash of order.
-    function getOrderHash(address[5] orderAddresses, uint256[6] orderValues)
-        public view
-        returns (bytes32 orderHash);
-
-    /// @dev Verifies that an order signature is valid.
-    /// @param signer address of signer.
-    /// @param hash Signed Keccak-256 hash.
-    /// @param v ECDSA signature parameter v.
-    /// @param r ECDSA signature parameters r.
-    /// @param s ECDSA signature parameters s.
-    /// @return Validity of order signature.
-    function isValidSignature(
-        address signer,
-        bytes32 hash,
-        uint8 v,
-        bytes32 r,
-        bytes32 s)
-        public pure
-        returns (bool isValid);
-
-    /// @dev Fills the input order.
-    /// @param orderAddresses Array of order's maker, taker, makerAsset, takerAsset, and feeRecipient.
-    /// @param orderValues Array of order's makerAssetAmount, takerAssetAmount, makerFee, takerFee, expirationTimestampInSec, and salt.
-    /// @param takerAssetFillAmount Desired amount of takerAsset to fill.
-    /// @param v ECDSA signature parameter v.
-    /// @param r ECDSA signature parameters r.
-    /// @param s ECDSA signature parameters s.
-    /// @return Total amount of takerAsset filled in trade.
-    function fillOrder(
-          address[5] orderAddresses,
-          uint256[6] orderValues,
-          uint256 takerAssetFillAmount,
-          uint8 v,
-          bytes32 r,
-          bytes32 s)
-          public
-          returns (uint256 takerAssetFilledAmount);
-
-    /// @dev Cancels the input order.
-    /// @param orderAddresses Array of order's maker, taker, makerAsset, takerAsset, and feeRecipient.
-    /// @param orderValues Array of order's makerAssetAmount, takerAssetAmount, makerFee, takerFee, expirationTimestampInSec, and salt.
-    /// @param takerAssetCancelAmount Desired amount of takerAsset to cancel in order.
-    /// @return Amount of takerAsset cancelled.
-    function cancelOrder(
-        address[5] orderAddresses,
-        uint256[6] orderValues,
-        uint256 takerAssetCancelAmount)
-        public
-        returns (uint256 takerAssetCancelledAmount);
-
-    /// @dev Cancels all orders for a specified maker up to a certain time.
-    /// @param salt Orders created with a salt less or equal to this value will be cancelled.
-    function cancelOrdersUpTo(uint256 salt)
-        external;
-
-    /// @dev Fills an order with specified parameters and ECDSA signature. Throws if specified amount not filled entirely.
-    /// @param orderAddresses Array of order's maker, taker, makerAsset, takerAsset, and feeRecipient.
-    /// @param orderValues Array of order's makerAssetAmount, takerAssetAmount, makerFee, takerFee, expirationTimestampInSec, and salt.
-    /// @param takerAssetFillAmount Desired amount of takerAsset to fill.
-    /// @param v ECDSA signature parameter v.
-    /// @param r ECDSA signature parameters r.
-    /// @param s ECDSA signature parameters s.
-    function fillOrKillOrder(
-        address[5] orderAddresses,
-        uint256[6] orderValues,
-        uint256 takerAssetFillAmount,
-        uint8 v,
-        bytes32 r,
-        bytes32 s)
-        public;
-
-    /// @dev Fills an order with specified parameters and ECDSA signature. Returns false if the transaction would otherwise revert.
-    /// @param orderAddresses Array of order's maker, taker, makerAsset, takerAsset, and feeRecipient.
-    /// @param orderValues Array of order's makerAssetAmount, takerAssetAmount, makerFee, takerFee, expirationTimestampInSec, and salt.
-    /// @param takerAssetFillAmount Desired amount of takerAsset to fill.
-    /// @param v ECDSA signature parameter v.
-    /// @param r ECDSA signature parameters r.
-    /// @param s ECDSA signature parameters s.
-    /// @return Success if the transaction did not revert.
-    /// @return Total amount of takerAsset filled in trade.
-    function fillOrderNoThrow(
-        address[5] orderAddresses,
-        uint256[6] orderValues,
-        uint256 takerAssetFillAmount,
-        uint8 v,
-        bytes32 r,
-        bytes32 s)
-        public
-        returns (bool success, uint256 takerAssetFilledAmount);
-
-    /// @dev Synchronously executes multiple calls of fillOrder in a single transaction.
-    /// @param orderAddresses Array of address arrays containing individual order addresses.
-    /// @param orderValues Array of uint256 arrays containing individual order values.
-    /// @param takerAssetFillAmounts Array of desired amounts of takerAsset to fill in orders.
-    /// @param v Array ECDSA signature v parameters.
-    /// @param r Array of ECDSA signature r parameters.
-    /// @param s Array of ECDSA signature s parameters.
-    function batchFillOrders(
-        address[5][] orderAddresses,
-        uint256[6][] orderValues,
-        uint256[] takerAssetFillAmounts,
-        uint8[] v,
-        bytes32[] r,
-        bytes32[] s)
-        external;
-
-    /// @dev Synchronously executes multiple calls of fillOrKill in a single transaction.
-    /// @param orderAddresses Array of address arrays containing individual order addresses.
-    /// @param orderValues Array of uint256 arrays containing individual order values.
-    /// @param takerAssetFillAmounts Array of desired amounts of takerAsset to fill in orders.
-    /// @param v Array ECDSA signature v parameters.
-    /// @param r Array of ECDSA signature r parameters.
-    /// @param s Array of ECDSA signature s parameters.
-    function batchFillOrKillOrders(
-        address[5][] orderAddresses,
-        uint256[6][] orderValues,
-        uint256[] takerAssetFillAmounts,
-        uint8[] v,
-        bytes32[] r,
-        bytes32[] s)
-        external;
-
-    /// @dev Synchronously executes multiple calls of fillOrderNoThrow in a single transaction.
-    /// @param orderAddresses Array of address arrays containing individual order addresses.
-    /// @param orderValues Array of uint256 arrays containing individual order values.
-    /// @param takerAssetFillAmounts Array of desired amounts of takerAsset to fill in orders.
-    /// @param v Array ECDSA signature v parameters.
-    /// @param r Array of ECDSA signature r parameters.
-    /// @param s Array of ECDSA signature s parameters.
-    function batchFillOrdersNoThrow(
-        address[5][] orderAddresses,
-        uint256[6][] orderValues,
-        uint256[] takerAssetFillAmounts,
-        uint8[] v,
-        bytes32[] r,
-        bytes32[] s)
-        external;
-
-    /// @dev Synchronously executes multiple fill orders in a single transaction until total takerAssetFillAmount filled.
-    /// @param orderAddresses Array of address arrays containing individual order addresses.
-    /// @param orderValues Array of uint256 arrays containing individual order values.
-    /// @param takerAssetFillAmount Desired total amount of takerAsset to fill in orders.
-    /// @param v Array ECDSA signature v parameters.
-    /// @param r Array of ECDSA signature r parameters.
-    /// @param s Array of ECDSA signature s parameters.
-    /// @return Total amount of takerAssetFillAmount filled in orders.
-    function marketFillOrders(
-        address[5][] orderAddresses,
-        uint256[6][] orderValues,
-        uint256 takerAssetFillAmount,
-        uint8[] v,
-        bytes32[] r,
-        bytes32[] s)
-        external
-        returns (uint256 totalTakerAssetFilledAmount);
-
-    /// @dev Synchronously executes multiple calls of fillOrderNoThrow in a single transaction until total takerAssetFillAmount filled.
-    /// @param orderAddresses Array of address arrays containing individual order addresses.
-    /// @param orderValues Array of uint256 arrays containing individual order values.
-    /// @param takerAssetFillAmount Desired total amount of takerAsset to fill in orders.
-    /// @param v Array ECDSA signature v parameters.
-    /// @param r Array of ECDSA signature r parameters.
-    /// @param s Array of ECDSA signature s parameters.
-    /// @return Total amount of takerAssetFillAmount filled in orders.
-    function marketFillOrdersNoThrow(
-        address[5][] orderAddresses,
-        uint256[6][] orderValues,
-        uint256 takerAssetFillAmount,
-        uint8[] v,
-        bytes32[] r,
-        bytes32[] s)
-        external
-        returns (uint256 totalTakerAssetFilledAmount);
-
-    /// @dev Synchronously cancels multiple orders in a single transaction.
-    /// @param orderAddresses Array of address arrays containing individual order addresses.
-    /// @param orderValues Array of uint256 arrays containing individual order values.
-    /// @param takerAssetCancelAmounts Array of desired amounts of takerAsset to cancel in orders.
-    function batchCancelOrders(
-        address[5][] orderAddresses,
-        uint256[6][] orderValues,
-        uint256[] takerAssetCancelAmounts)
-        external;
-}
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol
index b73c6ca90..308dace32 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol
@@ -16,43 +16,21 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
 
 import "../../utils/Ownable/Ownable.sol";
-import "../AssetProxy/IAssetProxy.sol";
+import "../AssetProxy/interfaces/IAssetProxy.sol";
+import "./libs/LibExchangeErrors.sol";
 import "./mixins/MAssetProxyDispatcher.sol";
 
 contract MixinAssetProxyDispatcher is
+    LibExchangeErrors,
     Ownable,
     MAssetProxyDispatcher
 {
     // Mapping from Asset Proxy Id's to their respective Asset Proxy
     mapping (uint8 => IAssetProxy) public assetProxies;
 
-    /// @dev Forwards arguments to assetProxy and calls `transferFrom`. Either succeeds or throws.
-    /// @param assetMetadata Byte array encoded for the respective asset proxy.
-    /// @param from Address to transfer token from.
-    /// @param to Address to transfer token to.
-    /// @param amount Amount of token to transfer.
-    function dispatchTransferFrom(
-        bytes memory assetMetadata,
-        address from,
-        address to,
-        uint256 amount)
-        internal
-    {
-        // Do nothing if no amount should be transferred.
-        if (amount > 0) {
-            // Lookup asset proxy.
-            require(assetMetadata.length >= 1);
-            uint8 assetProxyId = uint8(assetMetadata[0]);
-            IAssetProxy assetProxy = assetProxies[assetProxyId];
-
-            // transferFrom will either succeed or throw.
-            assetProxy.transferFrom(assetMetadata, from, to, amount);
-        }
-    }
-
     /// @dev Registers an asset proxy to an asset proxy id.
     ///      An id can only be assigned to a single proxy at a given time.
     /// @param assetProxyId Id to register`newAssetProxy` under.
@@ -65,15 +43,21 @@ contract MixinAssetProxyDispatcher is
         external
         onlyOwner
     {
-        // Ensure the existing asset proxy is not unintentionally overwritten.
-        require(oldAssetProxy == address(assetProxies[assetProxyId]));
+        // Ensure the existing asset proxy is not unintentionally overwritten
+        require(
+            oldAssetProxy == address(assetProxies[assetProxyId]),
+            OLD_ASSET_PROXY_MISMATCH
+        );
 
         IAssetProxy assetProxy = IAssetProxy(newAssetProxy);
 
         // Ensure that the id of newAssetProxy matches the passed in assetProxyId, unless it is being reset to 0.
         if (newAssetProxy != address(0)) {
             uint8 newAssetProxyId = assetProxy.getProxyId();
-            require(newAssetProxyId == assetProxyId);
+            require(
+                newAssetProxyId == assetProxyId,
+                NEW_ASSET_PROXY_MISMATCH
+            );
         }
 
         // Add asset proxy and log registration.
@@ -89,7 +73,34 @@ contract MixinAssetProxyDispatcher is
         view
         returns (address)
     {
-        IAssetProxy assetProxy = assetProxies[assetProxyId];
-        return address(assetProxy);
+        address assetProxy = address(assetProxies[assetProxyId]);
+        return assetProxy;
+    }
+
+    /// @dev Forwards arguments to assetProxy and calls `transferFrom`. Either succeeds or throws.
+    /// @param assetMetadata Byte array encoded for the respective asset proxy.
+    /// @param from Address to transfer token from.
+    /// @param to Address to transfer token to.
+    /// @param amount Amount of token to transfer.
+    function dispatchTransferFrom(
+        bytes memory assetMetadata,
+        address from,
+        address to,
+        uint256 amount)
+        internal
+    {
+        // Do nothing if no amount should be transferred.
+        if (amount > 0) {
+            // Lookup asset proxy
+            require(
+                assetMetadata.length >= 1,
+                GT_ZERO_LENGTH_REQUIRED
+            );
+            uint8 assetProxyId = uint8(assetMetadata[0]);
+            IAssetProxy assetProxy = assetProxies[assetProxyId];
+
+            // transferFrom will either succeed or throw.
+            assetProxy.transferFrom(assetMetadata, from, to, amount);
+        }
     }
 }
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinExchangeCore.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinExchangeCore.sol
index 4ca271b2a..82c7a2ddc 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinExchangeCore.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinExchangeCore.sol
@@ -16,26 +16,23 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
 pragma experimental ABIEncoderV2;
 
-import "./LibFillResults.sol";
-import "./LibOrder.sol";
-import "./LibErrors.sol";
-import "./LibMath.sol";
+import "./libs/LibFillResults.sol";
+import "./libs/LibOrder.sol";
+import "./libs/LibMath.sol";
+import "./libs/LibExchangeErrors.sol";
 import "./mixins/MExchangeCore.sol";
 import "./mixins/MSettlement.sol";
 import "./mixins/MSignatureValidator.sol";
 import "./mixins/MTransactions.sol";
 
-/// @dev Provides MExchangeCore
-/// @dev Consumes MSettlement
-/// @dev Consumes MSignatureValidator
 contract MixinExchangeCore is
     LibOrder,
     LibFillResults,
-    LibErrors,
     LibMath,
+    LibExchangeErrors,
     MExchangeCore,
     MSettlement,
     MSignatureValidator,
@@ -51,35 +48,19 @@ contract MixinExchangeCore is
     // Orders with a salt less than their maker's epoch are considered cancelled
     mapping (address => uint256) public makerEpoch;
 
-    event Fill(
-        address indexed makerAddress,
-        address takerAddress,
-        address indexed feeRecipientAddress,
-        uint256 makerAssetFilledAmount,
-        uint256 takerAssetFilledAmount,
-        uint256 makerFeePaid,
-        uint256 takerFeePaid,
-        bytes32 indexed orderHash,
-        bytes makerAssetData,
-        bytes takerAssetData
-    );
-
-    event Cancel(
-        address indexed makerAddress,
-        address indexed feeRecipientAddress,
-        bytes32 indexed orderHash,
-        bytes makerAssetData,
-        bytes takerAssetData
-    );
-
-    event CancelUpTo(
-        address indexed makerAddress,
-        uint256 makerEpoch
-    );
-
-    /*
-    * Core exchange functions
-    */
+    /// @dev Cancels all orders reated by sender with a salt less than or equal to the specified salt value.
+    /// @param salt Orders created with a salt less or equal to this value will be cancelled.
+    function cancelOrdersUpTo(uint256 salt)
+        external
+    {
+        uint256 newMakerEpoch = salt + 1;  // makerEpoch is initialized to 0, so to cancelUpTo we need salt + 1
+        require(
+            newMakerEpoch > makerEpoch[msg.sender],  // epoch must be monotonically increasing
+            INVALID_NEW_MAKER_EPOCH
+        );
+        makerEpoch[msg.sender] = newMakerEpoch;
+        emit CancelUpTo(msg.sender, newMakerEpoch);
+    }
 
     /// @dev Fills the input order.
     /// @param order Order struct containing order specifications.
@@ -111,22 +92,40 @@ contract MixinExchangeCore is
         // Validate order and maker only if first time seen
         // TODO: Read filled and cancelled only once
         if (filled[orderHash] == 0) {
-            require(order.makerAssetAmount > 0);
-            require(order.takerAssetAmount > 0);
-            require(isValidSignature(orderHash, order.makerAddress, signature));
+            require(
+                order.makerAssetAmount > 0,
+                GT_ZERO_AMOUNT_REQUIRED
+            );
+            require(
+                order.takerAssetAmount > 0,
+                GT_ZERO_AMOUNT_REQUIRED
+            );
+            require(
+                isValidSignature(orderHash, order.makerAddress, signature),
+                SIGNATURE_VALIDATION_FAILED
+            );
         }
         
         // Validate sender is allowed to fill this order
         if (order.senderAddress != address(0)) {
-            require(order.senderAddress == msg.sender);
+            require(
+                order.senderAddress == msg.sender,
+                INVALID_SENDER
+            );
         }
 
         // Validate taker is allowed to fill this order
         address takerAddress = getCurrentContextAddress();
         if (order.takerAddress != address(0)) {
-            require(order.takerAddress == takerAddress);
+            require(
+                order.takerAddress == takerAddress,
+                INVALID_CONTEXT
+            );
         }
-        require(takerAssetFillAmount > 0);
+        require(
+            takerAssetFillAmount > 0,
+            GT_ZERO_AMOUNT_REQUIRED
+        );
 
         // Validate order expiration
         if (block.timestamp >= order.expirationTimeSeconds) {
@@ -173,17 +172,29 @@ contract MixinExchangeCore is
         bytes32 orderHash = getOrderHash(order);
 
         // Validate the order
-        require(order.makerAssetAmount > 0);
-        require(order.takerAssetAmount > 0);
+        require(
+            order.makerAssetAmount > 0,
+            GT_ZERO_AMOUNT_REQUIRED
+        );
+        require(
+            order.takerAssetAmount > 0,
+            GT_ZERO_AMOUNT_REQUIRED
+        );
 
         // Validate sender is allowed to cancel this order
         if (order.senderAddress != address(0)) {
-            require(order.senderAddress == msg.sender);
+            require(
+                order.senderAddress == msg.sender,
+                INVALID_SENDER
+            );
         }
         
         // Validate transaction signed by maker
         address makerAddress = getCurrentContextAddress();
-        require(order.makerAddress == makerAddress);
+        require(
+            order.makerAddress == makerAddress,
+            INVALID_CONTEXT
+        );
         
         if (block.timestamp >= order.expirationTimeSeconds) {
             emit ExchangeError(uint8(Errors.ORDER_EXPIRED), orderHash);
@@ -207,16 +218,6 @@ contract MixinExchangeCore is
         return true;
     }
 
-    /// @param salt Orders created with a salt less or equal to this value will be cancelled.
-    function cancelOrdersUpTo(uint256 salt)
-        external
-    {
-        uint256 newMakerEpoch = salt + 1;                // makerEpoch is initialized to 0, so to cancelUpTo we need salt+1
-        require(newMakerEpoch > makerEpoch[msg.sender]); // epoch must be monotonically increasing
-        makerEpoch[msg.sender] = newMakerEpoch;
-        emit CancelUpTo(msg.sender, newMakerEpoch);
-    }
-
     /// @dev Logs a Fill event with the given arguments.
     ///      The sole purpose of this function is to get around the stack variable limit.
     function emitFillEvent(
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinSettlement.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinSettlement.sol
index cab2ccfb6..30f1bb49b 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinSettlement.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinSettlement.sol
@@ -16,23 +16,24 @@
 
 */
 
-pragma solidity ^0.4.21;
-pragma experimental ABIEncoderV2;
+pragma solidity ^0.4.23;
 
 import "./mixins/MSettlement.sol";
 import "./mixins/MAssetProxyDispatcher.sol";
-import "./LibOrder.sol";
-import "./LibMath.sol";
-import "../AssetProxy/IAssetProxy.sol";
+import "./libs/LibOrder.sol";
+import "./libs/LibMath.sol";
 
-/// @dev Provides MixinSettlement
 contract MixinSettlement is
     LibMath,
     MSettlement,
     MAssetProxyDispatcher
 {
+    // ZRX metadata used for fee transfers.
+    // This will be constant throughout the life of the Exchange contract,
+    // since ZRX will always be transferred via the ERC20 AssetProxy.
     bytes internal ZRX_PROXY_DATA;
 
+    /// @dev Gets the ZRX metadata used for fee transfers.
     function zrxProxyData()
         external
         view
@@ -41,12 +42,20 @@ contract MixinSettlement is
         return ZRX_PROXY_DATA;
     }
 
-    function MixinSettlement(bytes memory _zrxProxyData)
+    /// TODO: _zrxProxyData should be a constant in production.
+    /// @dev Constructor sets the metadata that will be used for paying ZRX fees.
+    /// @param _zrxProxyData Byte array containing ERC20 proxy id concatenated with address of ZRX.
+    constructor (bytes memory _zrxProxyData)
         public
     {
         ZRX_PROXY_DATA = _zrxProxyData;
     }
 
+    /// @dev Settles an order by transferring assets between counterparties.
+    /// @param order Order struct containing order specifications.
+    /// @param takerAddress Address selling takerAsset and buying makerAsset.
+    /// @param takerAssetFilledAmount The amount of takerAsset that will be transferred to the order's maker.
+    /// @return Amount filled by maker and fees paid by maker/taker.
     function settleOrder(
         LibOrder.Order memory order,
         address takerAddress,
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol
index 690a70820..2322625d9 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol
@@ -16,29 +16,39 @@
 
 */
 
-pragma solidity ^0.4.21;
-pragma experimental ABIEncoderV2;
+pragma solidity ^0.4.23;
 
 import "./mixins/MSignatureValidator.sol";
-import "./ISigner.sol";
-
-/// @dev Provides MSignatureValidator
-contract MixinSignatureValidator is MSignatureValidator {
-
-    enum SignatureType {
-        Illegal, // Default value
-        Invalid,
-        Caller,
-        Ecrecover,
-        EIP712,
-        Trezor,
-        Contract,
-        PreSigned
-    }
+import "./interfaces/ISigner.sol";
+import "./libs/LibExchangeErrors.sol";
+import "../../utils/LibBytes/LibBytes.sol";
+
+contract MixinSignatureValidator is
+    LibBytes,
+    LibExchangeErrors,
+    MSignatureValidator
+{
 
     // Mapping of hash => signer => signed
     mapping(bytes32 => mapping(address => bool)) preSigned;
 
+    /// @dev Approves a hash on-chain using any valid signature type.
+    ///      After presigning a hash, the preSign signature type will become valid for that hash and signer.
+    /// @param signer Address that should have signed the given hash.
+    /// @param signature Proof that the hash has been signed by signer.
+    function preSign(
+        bytes32 hash,
+        address signer,
+        bytes signature)
+        external
+    {
+        require(
+            isValidSignature(hash, signer, signature),
+            SIGNATURE_VALIDATION_FAILED
+        );
+        preSigned[hash][signer] = true;
+    }
+
     /// @dev Verifies that a hash has been signed by the given signer.
     /// @param hash Any 32 byte hash.
     /// @param signer Address that should have signed the given hash.
@@ -54,7 +64,10 @@ contract MixinSignatureValidator is MSignatureValidator {
     {
         // TODO: Domain separation: make hash depend on role. (Taker sig should not be valid as maker sig, etc.)
 
-        require(signature.length >= 1);
+        require(
+            signature.length >= 1,
+            INVALID_SIGNATURE_LENGTH
+        );
         SignatureType signatureType = SignatureType(uint8(signature[0]));
 
         // Variables are not scoped in Solidity
@@ -69,14 +82,18 @@ contract MixinSignatureValidator is MSignatureValidator {
         // it an explicit option. This aids testing and analysis. It is
         // also the initialization value for the enum type.
         if (signatureType == SignatureType.Illegal) {
-            revert();
+            // NOTE: Reason cannot be assigned to a variable because of https://github.com/ethereum/solidity/issues/4051
+            revert("Illegal signature type.");
 
         // Always invalid signature
         // Like Illegal, this is always implicitly available and therefore
         // offered explicitly. It can be implicitly created by providing
         // a correctly formatted but incorrect signature.
         } else if (signatureType == SignatureType.Invalid) {
-            require(signature.length == 1);
+            require(
+                signature.length == 1,
+                INVALID_SIGNATURE_LENGTH
+            );
             isValid = false;
             return isValid;
 
@@ -89,16 +106,22 @@ contract MixinSignatureValidator is MSignatureValidator {
         // `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 == 1);
+            require(
+                signature.length == 1,
+                INVALID_SIGNATURE_LENGTH
+            );
             isValid = signer == msg.sender;
             return isValid;
 
         // Signed using web3.eth_sign
         } else if (signatureType == SignatureType.Ecrecover) {
-            require(signature.length == 66);
+            require(
+                signature.length == 66,
+                INVALID_SIGNATURE_LENGTH
+            );
             v = uint8(signature[1]);
-            r = get32(signature, 2);
-            s = get32(signature, 34);
+            r = readBytes32(signature, 2);
+            s = readBytes32(signature, 34);
             recovered = ecrecover(
                 keccak256("\x19Ethereum Signed Message:\n32", hash),
                 v,
@@ -110,10 +133,13 @@ contract MixinSignatureValidator is MSignatureValidator {
 
         // Signature using EIP712
         } else if (signatureType == SignatureType.EIP712) {
-            require(signature.length == 66);
+            require(
+                signature.length == 66,
+                INVALID_SIGNATURE_LENGTH
+            );
             v = uint8(signature[1]);
-            r = get32(signature, 2);
-            s = get32(signature, 34);
+            r = readBytes32(signature, 2);
+            s = readBytes32(signature, 34);
             recovered = ecrecover(hash, v, r, s);
             isValid = signer == recovered;
             return isValid;
@@ -127,10 +153,13 @@ contract MixinSignatureValidator is MSignatureValidator {
         // 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 == 66);
+            require(
+                signature.length == 66,
+                INVALID_SIGNATURE_LENGTH
+            );
             v = uint8(signature[1]);
-            r = get32(signature, 2);
-            s = get32(signature, 34);
+            r = readBytes32(signature, 2);
+            s = readBytes32(signature, 34);
             recovered = ecrecover(
                 keccak256("\x19Ethereum Signed Message:\n\x41", hash),
                 v,
@@ -156,37 +185,7 @@ contract MixinSignatureValidator is MSignatureValidator {
         // that we currently support. In this case returning false
         // may lead the caller to incorrectly believe that the
         // signature was invalid.)
-        revert();
+        // NOTE: Reason cannot be assigned to a variable because of https://github.com/ethereum/solidity/issues/4051
+        revert("Unsupported signature type.");
     }
-
-    /// @dev Approves a hash on-chain using any valid signature type.
-    ///      After presigning a hash, the preSign signature type will become valid for that hash and signer.
-    /// @param signer Address that should have signed the given hash.
-    /// @param signature Proof that the hash has been signed by signer.
-    function preSign(
-        bytes32 hash,
-        address signer,
-        bytes signature)
-        external
-    {
-        require(isValidSignature(hash, signer, signature));
-        preSigned[hash][signer] = true;
-    }
-
-    function get32(bytes memory b, uint256 index)
-        private pure
-        returns (bytes32 result)
-    {
-        require(b.length >= index + 32);
-
-        // Arrays are prefixed by a 256 bit length parameter
-        index += 32;
-
-        // Read the bytes32 from array memory
-        assembly {
-            result := mload(add(b, index))
-        }
-        return result;
-    }
-
 }
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinTransactions.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinTransactions.sol
index 9edb1694f..7f12834a3 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinTransactions.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinTransactions.sol
@@ -16,12 +16,13 @@
 
 */
 pragma solidity ^0.4.21;
-pragma experimental ABIEncoderV2;
 
 import "./mixins/MSignatureValidator.sol";
 import "./mixins/MTransactions.sol";
+import "./libs/LibExchangeErrors.sol";
 
 contract MixinTransactions is
+    LibExchangeErrors,
     MSignatureValidator,
     MTransactions
 {
@@ -56,12 +57,18 @@ contract MixinTransactions is
         );
 
         // Validate transaction has not been executed
-        require(!transactions[transactionHash]);
+        require(
+            !transactions[transactionHash],
+            DUPLICATE_TRANSACTION_HASH
+        );
 
         // TODO: is SignatureType.Caller necessary if we make this check?
         if (signer != msg.sender) {
             // Validate signature
-            require(isValidSignature(transactionHash, signer, signature));
+            require(
+                isValidSignature(transactionHash, signer, signature),
+                SIGNATURE_VALIDATION_FAILED
+            );
 
             // Set the current transaction signer
             currentContextAddress = signer;
@@ -69,7 +76,10 @@ contract MixinTransactions is
 
         // Execute transaction
         transactions[transactionHash] = true;
-        require(address(this).delegatecall(data));
+        require(
+            address(this).delegatecall(data),
+            TRANSACTION_EXECUTION_FAILED
+        );
 
         // Reset current transaction signer
         // TODO: Check if gas is paid when currentContextAddress is already 0.
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinWrapperFunctions.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinWrapperFunctions.sol
index 105c0f0a0..42517221e 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinWrapperFunctions.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinWrapperFunctions.sol
@@ -16,21 +16,22 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
 pragma experimental ABIEncoderV2;
 
 import "../../utils/LibBytes/LibBytes.sol";
 import "./mixins/MExchangeCore.sol";
-import "./LibMath.sol";
-import "./LibOrder.sol";
-import "./LibFillResults.sol";
+import "./libs/LibMath.sol";
+import "./libs/LibOrder.sol";
+import "./libs/LibFillResults.sol";
+import "./libs/LibExchangeErrors.sol";
 
-/// @dev Consumes MExchangeCore
 contract MixinWrapperFunctions is
     LibOrder,
     LibFillResults,
     LibMath,
     LibBytes,
+    LibExchangeErrors,
     MExchangeCore
 {
     /// @dev Fills the input order. Reverts if exact takerAssetFillAmount not filled.
@@ -49,7 +50,10 @@ contract MixinWrapperFunctions is
             takerAssetFillAmount,
             signature
         );
-        require(fillResults.takerAssetFilledAmount == takerAssetFillAmount);
+        require(
+            fillResults.takerAssetFilledAmount == takerAssetFillAmount,
+            COMPLETE_FILL_FAILED
+        );
         return fillResults;
     }
 
@@ -327,7 +331,11 @@ contract MixinWrapperFunctions is
         for (uint256 i = 0; i < orders.length; i++) {
 
             // Token being sold by taker must be the same for each order
-            require(areBytesEqual(orders[i].takerAssetData, orders[0].takerAssetData));
+            // TODO: optimize by only using takerAssetData for first order.
+            require(
+                areBytesEqual(orders[i].takerAssetData, orders[0].takerAssetData),
+                ASSET_DATA_MISMATCH
+            );
 
             // Calculate the remaining amount of takerAsset to sell
             uint256 remainingTakerAssetFillAmount = safeSub(takerAssetFillAmount, totalFillResults.takerAssetFilledAmount);
@@ -366,7 +374,11 @@ contract MixinWrapperFunctions is
         for (uint256 i = 0; i < orders.length; i++) {
 
             // Token being sold by taker must be the same for each order
-            require(areBytesEqual(orders[i].takerAssetData, orders[0].takerAssetData));
+            // TODO: optimize by only using takerAssetData for first order.
+            require(
+                areBytesEqual(orders[i].takerAssetData, orders[0].takerAssetData),
+                ASSET_DATA_MISMATCH
+            );
 
             // Calculate the remaining amount of takerAsset to sell
             uint256 remainingTakerAssetFillAmount = safeSub(takerAssetFillAmount, totalFillResults.takerAssetFilledAmount);
@@ -404,7 +416,11 @@ contract MixinWrapperFunctions is
         for (uint256 i = 0; i < orders.length; i++) {
 
             // Token being bought by taker must be the same for each order
-            require(areBytesEqual(orders[i].makerAssetData, orders[0].makerAssetData));
+            // TODO: optimize by only using makerAssetData for first order.
+            require(
+                areBytesEqual(orders[i].makerAssetData, orders[0].makerAssetData),
+                ASSET_DATA_MISMATCH
+            );
 
             // Calculate the remaining amount of makerAsset to buy
             uint256 remainingMakerAssetFillAmount = safeSub(makerAssetFillAmount, totalFillResults.makerAssetFilledAmount);
@@ -451,7 +467,11 @@ contract MixinWrapperFunctions is
         for (uint256 i = 0; i < orders.length; i++) {
 
             // Token being bought by taker must be the same for each order
-            require(areBytesEqual(orders[i].makerAssetData, orders[0].makerAssetData));
+            // TODO: optimize by only using makerAssetData for first order.
+            require(
+                areBytesEqual(orders[i].makerAssetData, orders[0].makerAssetData),
+                ASSET_DATA_MISMATCH
+            );
 
             // Calculate the remaining amount of makerAsset to buy
             uint256 remainingMakerAssetFillAmount = safeSub(makerAssetFillAmount, totalFillResults.makerAssetFilledAmount);
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IAssetProxyDispatcher.sol b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IAssetProxyDispatcher.sol
new file mode 100644
index 000000000..4e4ed6be8
--- /dev/null
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IAssetProxyDispatcher.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 ^0.4.23;
+
+contract IAssetProxyDispatcher {
+
+    /// @dev Registers an asset proxy to an asset proxy id.
+    ///      An id can only be assigned to a single proxy at a given time.
+    /// @param assetProxyId Id to register`newAssetProxy` under.
+    /// @param newAssetProxy Address of new asset proxy to register, or 0x0 to unset assetProxyId.
+    /// @param oldAssetProxy Existing asset proxy to overwrite, or 0x0 if assetProxyId is currently unused.
+    function registerAssetProxy(
+        uint8 assetProxyId,
+        address newAssetProxy,
+        address oldAssetProxy)
+        external;
+
+    /// @dev Gets an asset proxy.
+    /// @param assetProxyId Id of the asset proxy.
+    /// @return The asset proxy registered to assetProxyId. Returns 0x0 if no proxy is registered.
+    function getAssetProxy(uint8 assetProxyId)
+        external
+        view
+        returns (address);
+}
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IExchange.sol b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IExchange.sol
new file mode 100644
index 000000000..9fba3491b
--- /dev/null
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IExchange.sol
@@ -0,0 +1,34 @@
+/*
+
+  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 ^0.4.23;
+pragma experimental ABIEncoderV2;
+
+import "./IExchangeCore.sol";
+import "./ISignatureValidator.sol";
+import "./IAssetProxyDispatcher.sol";
+import "./ITransactions.sol";
+import "./IWrapperFunctions.sol";
+
+contract IExchange is
+    IWrapperFunctions,
+    IExchangeCore,
+    ISignatureValidator,
+    ITransactions,
+    IAssetProxyDispatcher
+{}
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IExchangeCore.sol b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IExchangeCore.sol
new file mode 100644
index 000000000..0f19525ca
--- /dev/null
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IExchangeCore.sol
@@ -0,0 +1,51 @@
+/*
+
+  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 ^0.4.23;
+pragma experimental ABIEncoderV2;
+
+import "../libs/LibOrder.sol";
+import "../libs/LibFillResults.sol";
+
+contract IExchangeCore {
+
+    /// @dev Cancels all orders reated by sender with a salt less than or equal to the specified salt value.
+    /// @param salt Orders created with a salt less or equal to this value will be cancelled.
+    function cancelOrdersUpTo(uint256 salt)
+        external;
+
+    /// @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 fillOrder(
+        LibOrder.Order memory order,
+        uint256 takerAssetFillAmount,
+        bytes memory signature)
+        public
+        returns (LibFillResults.FillResults memory fillResults);
+
+    /// @dev After calling, the order can not be filled anymore.
+    /// @param order Order struct containing order specifications.
+    /// @return True if the order state changed to cancelled.
+    ///         False if the transaction was already cancelled or expired.
+    function cancelOrder(LibOrder.Order memory order)
+        public
+        returns (bool);
+}
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/ISignatureValidator.sol b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/ISignatureValidator.sol
new file mode 100644
index 000000000..b4a238472
--- /dev/null
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/ISignatureValidator.sol
@@ -0,0 +1,32 @@
+/*
+
+  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 ^0.4.23;
+
+contract ISignatureValidator {
+
+    /// @dev Approves a hash on-chain using any valid signature type.
+    ///      After presigning a hash, the preSign signature type will become valid for that hash and signer.
+    /// @param signer Address that should have signed the given hash.
+    /// @param signature Proof that the hash has been signed by signer.
+    function preSign(
+        bytes32 hash,
+        address signer,
+        bytes signature)
+        external;
+}
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/ISigner.sol b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/ISigner.sol
index d5641a09f..e065cfd8a 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/ISigner.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/ISigner.sol
@@ -16,11 +16,14 @@
 
 */
 
-pragma solidity ^0.4.21;
-pragma experimental ABIEncoderV2;
+pragma solidity ^0.4.23;
 
 contract ISigner {
 
+    /// @dev Verifies that a signature is valid.
+    /// @param hash Message hash that is signed.
+    /// @param signature Proof of signing.
+    /// @return Validity of order signature.
     function isValidSignature(
         bytes32 hash,
         bytes signature)
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/ITransactions.sol b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/ITransactions.sol
new file mode 100644
index 000000000..76e4cf2fe
--- /dev/null
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/ITransactions.sol
@@ -0,0 +1,33 @@
+/*
+
+  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 ^0.4.23;
+
+contract ITransactions {
+
+    /// @dev Executes an exchange method call in the context of signer.
+    /// @param salt Arbitrary number to ensure uniqueness of transaction hash.
+    /// @param signer Address of transaction signer.
+    /// @param data AbiV2 encoded calldata.
+    /// @param signature Proof of signer transaction by signer.
+    function executeTransaction(
+        uint256 salt,
+        address signer,
+        bytes data,
+        bytes signature)
+        external;
+}
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IWrapperFunctions.sol b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IWrapperFunctions.sol
new file mode 100644
index 000000000..d23170b1c
--- /dev/null
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IWrapperFunctions.sol
@@ -0,0 +1,142 @@
+/*
+
+  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 ^0.4.23;
+pragma experimental ABIEncoderV2;
+
+import "./libs/LibOrder.sol";
+import "./libs/LibFillResults.sol";
+
+contract IWrapperFunctions is
+    LibOrder,
+    LibFillResults,
+    LibMath,
+    LibBytes,
+    LibExchangeErrors,
+    MExchangeCore
+{
+    /// @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 fillOrKillOrder(
+        LibOrder.LibOrder.Order memory order,
+        uint256 takerAssetFillAmount,
+        bytes memory signature)
+        public
+        returns (LibFillResults.LibFillResults.FillResults memory fillResults);
+
+    /// @dev Fills an order with specified parameters and ECDSA signature.
+    ///      Returns false if the transaction would otherwise revert.
+    /// @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.
+    /// @return Amounts filled and fees paid by maker and taker.
+    function fillOrderNoThrow(
+        LibOrder.Order memory order,
+        uint256 takerAssetFillAmount,
+        bytes memory signature)
+        public
+        returns (LibFillResults.FillResults memory fillResults);
+
+    /// @dev Synchronously executes multiple calls of fillOrder.
+    /// @param orders Array of order specifications.
+    /// @param takerAssetFillAmounts Array of desired amounts of takerAsset to sell in orders.
+    /// @param signatures Proofs that orders have been created by makers.
+    function batchFillOrders(
+        LibOrder.Order[] memory orders,
+        uint256[] memory takerAssetFillAmounts,
+        bytes[] memory signatures)
+        public;
+
+    /// @dev Synchronously executes multiple calls of fillOrKill.
+    /// @param orders Array of order specifications.
+    /// @param takerAssetFillAmounts Array of desired amounts of takerAsset to sell in orders.
+    /// @param signatures Proofs that orders have been created by makers.
+    function batchFillOrKillOrders(
+        LibOrder.Order[] memory orders,
+        uint256[] memory takerAssetFillAmounts,
+        bytes[] memory signatures)
+        public;
+
+    /// @dev Fills an order with specified parameters and ECDSA signature.
+    ///      Returns false if the transaction would otherwise revert.
+    /// @param orders Array of order specifications.
+    /// @param takerAssetFillAmounts Array of desired amounts of takerAsset to sell in orders.
+    /// @param signatures Proofs that orders have been created by makers.
+    function batchFillOrdersNoThrow(
+        LibOrder.Order[] memory orders,
+        uint256[] memory takerAssetFillAmounts,
+        bytes[] memory signatures)
+        public;
+
+    /// @dev Synchronously executes multiple calls of fillOrder until total amount of takerAsset is sold by taker.
+    /// @param orders Array of order specifications.
+    /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
+    /// @param signatures Proofs that orders have been created by makers.
+    /// @return Amounts filled and fees paid by makers and taker.
+    function marketSellOrders(
+        LibOrder.Order[] memory orders,
+        uint256 takerAssetFillAmount,
+        bytes[] memory signatures)
+        public
+        returns (LibFillResults.FillResults memory totalFillResults);
+
+    /// @dev Synchronously executes multiple calls of fillOrder until total amount of takerAsset is sold by taker.
+    ///      Returns false if the transaction would otherwise revert.
+    /// @param orders Array of order specifications.
+    /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
+    /// @param signatures Proofs that orders have been signed by makers.
+    /// @return Amounts filled and fees paid by makers and taker.
+    function marketSellOrdersNoThrow(
+        LibOrder.Order[] memory orders,
+        uint256 takerAssetFillAmount,
+        bytes[] memory signatures)
+        public
+        returns (LibFillResults.FillResults memory totalFillResults);
+
+    /// @dev Synchronously executes multiple calls of fillOrder until total amount of makerAsset is bought by taker.
+    /// @param orders Array of order specifications.
+    /// @param makerAssetFillAmount Desired amount of makerAsset to buy.
+    /// @param signatures Proofs that orders have been signed by makers.
+    /// @return Amounts filled and fees paid by makers and taker.
+    function marketBuyOrders(
+        LibOrder.Order[] memory orders,
+        uint256 makerAssetFillAmount,
+        bytes[] memory signatures)
+        public
+        returns (LibFillResults.FillResults memory totalFillResults);
+
+    /// @dev Synchronously executes multiple fill orders in a single transaction until total amount is bought by taker.
+    ///      Returns false if the transaction would otherwise revert.
+    /// @param orders Array of order specifications.
+    /// @param makerAssetFillAmount Desired amount of makerAsset to buy.
+    /// @param signatures Proofs that orders have been signed by makers.
+    /// @return Amounts filled and fees paid by makers and taker.
+    function marketBuyOrdersNoThrow(
+        LibOrder.Order[] memory orders,
+        uint256 makerAssetFillAmount,
+        bytes[] memory signatures)
+        public
+        returns (LibFillResults.FillResults memory totalFillResults);
+
+    /// @dev Synchronously cancels multiple orders in a single transaction.
+    /// @param orders Array of order specifications.
+    function batchCancelOrders(LibOrder.Order[] memory orders)
+        public;
+}
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibExchangeErrors.sol b/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibExchangeErrors.sol
new file mode 100644
index 000000000..6ffbdfdca
--- /dev/null
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibExchangeErrors.sol
@@ -0,0 +1,58 @@
+/*
+
+  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 ^0.4.23;
+
+contract LibExchangeErrors {
+
+    // Error Codes
+    enum Errors {
+        ORDER_EXPIRED,                     // Order has already expired
+        ORDER_FULLY_FILLED,                // Order has already been fully filled
+        ORDER_CANCELLED,                   // Order has already been cancelled
+        ROUNDING_ERROR_TOO_LARGE,          // Rounding error too large
+        INSUFFICIENT_BALANCE_OR_ALLOWANCE  // Insufficient balance or allowance for token transfer
+    }
+
+    event ExchangeError(uint8 indexed errorId, bytes32 indexed orderHash);
+
+    // Core revert reasons
+    string constant GT_ZERO_AMOUNT_REQUIRED = "Amount must be greater than 0.";
+    string constant SIGNATURE_VALIDATION_FAILED = "Signature validation failed.";
+    string constant INVALID_SENDER = "Invalid `msg.sender`.";
+    string constant INVALID_CONTEXT = "Function called in an invalid context.";
+    string constant INVALID_NEW_MAKER_EPOCH = "Specified salt must be greater than or equal to existing makerEpoch.";
+
+    // Transaction revert reasons
+    string constant DUPLICATE_TRANSACTION_HASH = "Transaction has already been executed.";
+    string constant TRANSACTION_EXECUTION_FAILED = "Transaction execution failed.";
+
+    // Wrapper revert reasons
+    string constant COMPLETE_FILL_FAILED = "Desired fill amount could not be completely filled.";
+    string constant ASSET_DATA_MISMATCH = "Asset data must be the same for each order.";
+
+    // Asset proxy dispatcher revert reasons
+    string constant GT_ZERO_LENGTH_REQUIRED = "Length must be greater than 0.";
+    string constant OLD_ASSET_PROXY_MISMATCH = "Old asset proxy does not match asset proxy at given id.";
+    string constant NEW_ASSET_PROXY_MISMATCH = "New asset proxy id does not match given id.";
+
+    // Signature validator revert reasons
+    string constant INVALID_SIGNATURE_LENGTH = "Invalid signature length.";
+    string constant ILLEGAL_SIGNATURE_TYPE = "Illegal signature type.";
+    string constant UNSUPPORTED_SIGNATURE_TYPE = "Unsupported signature type.";
+}
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/LibFillResults.sol b/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibFillResults.sol
index 41096f448..3b8f2acf9 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/LibFillResults.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibFillResults.sol
@@ -16,12 +16,13 @@
 
 */
 
-pragma solidity ^0.4.21;
-pragma experimental ABIEncoderV2;
+pragma solidity ^0.4.23;
 
-import "../../utils/SafeMath/SafeMath.sol";
+import "../../../utils/SafeMath/SafeMath.sol";
 
-contract LibFillResults is SafeMath {
+contract LibFillResults is
+    SafeMath
+{
 
     struct FillResults {
         uint256 makerAssetFilledAmount;
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/LibMath.sol b/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibMath.sol
index 3b553ebbc..b48602d19 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/LibMath.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibMath.sol
@@ -16,12 +16,13 @@
 
 */
 
-pragma solidity ^0.4.21;
-pragma experimental ABIEncoderV2;
+pragma solidity ^0.4.23;
 
-import "../../utils/SafeMath/SafeMath.sol";
+import "../../../utils/SafeMath/SafeMath.sol";
 
-contract LibMath is SafeMath {
+contract LibMath is
+    SafeMath
+{
 
     /// @dev Calculates partial value given a numerator and denominator.
     /// @param numerator Numerator.
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/LibOrder.sol b/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibOrder.sol
index df974e177..0fe8c8c96 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/LibOrder.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibOrder.sol
@@ -16,8 +16,7 @@
 
 */
 
-pragma solidity ^0.4.21;
-pragma experimental ABIEncoderV2;
+pragma solidity ^0.4.23;
 
 contract LibOrder {
 
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MAssetProxyDispatcher.sol b/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
index 0cf750d7d..77ee77797 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
@@ -16,9 +16,13 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
 
-contract MAssetProxyDispatcher {
+import "../interfaces/IAssetProxyDispatcher.sol";
+
+contract MAssetProxyDispatcher is
+    IAssetProxyDispatcher
+{
 
     // Logs registration of new asset proxy
     event AssetProxySet(
@@ -38,23 +42,4 @@ contract MAssetProxyDispatcher {
         address to,
         uint256 amount)
         internal;
-
-    /// @dev Registers an asset proxy to an asset proxy id.
-    ///      An id can only be assigned to a single proxy at a given time.
-    /// @param assetProxyId Id to register`newAssetProxy` under.
-    /// @param newAssetProxy Address of new asset proxy to register, or 0x0 to unset assetProxyId.
-    /// @param oldAssetProxy Existing asset proxy to overwrite, or 0x0 if assetProxyId is currently unused.
-    function registerAssetProxy(
-        uint8 assetProxyId,
-        address newAssetProxy,
-        address oldAssetProxy)
-        external;
-
-    /// @dev Gets an asset proxy.
-    /// @param assetProxyId Id of the asset proxy.
-    /// @return The asset proxy registered to assetProxyId. Returns 0x0 if no proxy is registered.
-    function getAssetProxy(uint8 assetProxyId)
-        external
-        view
-        returns (address);
 }
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MExchangeCore.sol b/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MExchangeCore.sol
index 656df079e..5b78e70da 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MExchangeCore.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MExchangeCore.sol
@@ -16,25 +16,51 @@
 
 */
 
-pragma solidity ^0.4.21;
-pragma experimental ABIEncoderV2;
+pragma solidity ^0.4.23;
 
-import "../LibOrder.sol";
-import "../LibFillResults.sol";
+import "../libs/LibOrder.sol";
+import "../libs/LibFillResults.sol";
+import "../interfaces/IExchangeCore.sol";
 
-contract MExchangeCore {
+contract MExchangeCore is
+    IExchangeCore
+{
 
-    function fillOrder(
-        LibOrder.Order memory order,
-        uint256 takerAssetFillAmount,
-        bytes memory signature)
-        public
-        returns (LibFillResults.FillResults memory fillResults);
+    // Fill event is emitted whenever an order is filled.
+    event Fill(
+        address indexed makerAddress,
+        address takerAddress,
+        address indexed feeRecipientAddress,
+        uint256 makerAssetFilledAmount,
+        uint256 takerAssetFilledAmount,
+        uint256 makerFeePaid,
+        uint256 takerFeePaid,
+        bytes32 indexed orderHash,
+        bytes makerAssetData,
+        bytes takerAssetData
+    );
+
+    // Cancel event is emitted whenever an individual order is cancelled.
+    event Cancel(
+        address indexed makerAddress,
+        address indexed feeRecipientAddress,
+        bytes32 indexed orderHash,
+        bytes makerAssetData,
+        bytes takerAssetData
+    );
 
-    function cancelOrder(LibOrder.Order memory order)
-        public
-        returns (bool);
+    // CancelUpTo event is emitted whenever `cancelOrdersUpTo` is executed succesfully.
+    event CancelUpTo(
+        address indexed makerAddress,
+        uint256 makerEpoch
+    );
 
-    function cancelOrdersUpTo(uint256 salt)
-        external;
+    /// @dev Logs a Fill event with the given arguments.
+    ///      The sole purpose of this function is to get around the stack variable limit.
+    function emitFillEvent(
+        LibOrder.Order memory order,
+        address takerAddress,
+        bytes32 orderHash,
+        LibFillResults.FillResults memory fillResults)
+        internal;
 }
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MSettlement.sol b/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MSettlement.sol
index 0d7e59a9a..5e2edbf99 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MSettlement.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MSettlement.sol
@@ -16,13 +16,17 @@
 
 */
 
-pragma solidity ^0.4.21;
-pragma experimental ABIEncoderV2;
+pragma solidity ^0.4.23;
 
-import "../LibOrder.sol";
+import "../libs/LibOrder.sol";
 
 contract MSettlement {
 
+    /// @dev Settles an order by transfering assets between counterparties.
+    /// @param order Order struct containing order specifications.
+    /// @param takerAddress Address selling takerAsset and buying makerAsset.
+    /// @param takerAssetFilledAmount The amount of takerAsset that will be transfered to the order's maker.
+    /// @return Amount filled by maker and fees paid by maker/taker.
     function settleOrder(
         LibOrder.Order memory order,
         address takerAddress,
@@ -33,5 +37,5 @@ contract MSettlement {
             uint256 makerFeePaid,
             uint256 takerFeePaid
         );
-
 }
+
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MSignatureValidator.sol b/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MSignatureValidator.sol
index 043a7da9c..ba26c07f6 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MSignatureValidator.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MSignatureValidator.sol
@@ -16,10 +16,24 @@
 
 */
 
-pragma solidity ^0.4.21;
-pragma experimental ABIEncoderV2;
-
-contract MSignatureValidator {
+pragma solidity ^0.4.23;
+
+import "../interfaces/ISignatureValidator.sol";
+
+contract MSignatureValidator is
+    ISignatureValidator
+{
+    // Allowed signature types.
+    enum SignatureType {
+        Illegal,  // Default value
+        Invalid,
+        Caller,
+        Ecrecover,
+        EIP712,
+        Trezor,
+        Contract,
+        PreSigned
+    }
 
     /// @dev Verifies that a signature is valid.
     /// @param hash Message hash that is signed.
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MTransactions.sol b/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MTransactions.sol
index 10bfcb035..159ed1527 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MTransactions.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MTransactions.sol
@@ -15,24 +15,13 @@
   limitations under the License.
 
 */
-pragma solidity ^0.4.21;
-pragma experimental ABIEncoderV2;
-
-import "./MSignatureValidator.sol";
-
-contract MTransactions is MSignatureValidator {
-
-    /// @dev Executes an exchange method call in the context of signer.
-    /// @param salt Arbitrary number to ensure uniqueness of transaction hash.
-    /// @param signer Address of transaction signer.
-    /// @param data AbiV2 encoded calldata.
-    /// @param signature Proof of signer transaction by signer.
-    function executeTransaction(
-        uint256 salt,
-        address signer,
-        bytes data,
-        bytes signature)
-        external;
+pragma solidity ^0.4.23;
+
+import "../interfaces/ITransactions.sol";
+
+contract MTransactions is
+    ITransactions
+{
 
     /// @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/contracts/current/test/DummyERC20Token/DummyERC20Token.sol b/packages/contracts/src/contracts/current/test/DummyERC20Token/DummyERC20Token.sol
index 2626399c2..ab5311e0c 100644
--- a/packages/contracts/src/contracts/current/test/DummyERC20Token/DummyERC20Token.sol
+++ b/packages/contracts/src/contracts/current/test/DummyERC20Token/DummyERC20Token.sol
@@ -16,7 +16,8 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
+pragma experimental ABIEncoderV2;
 
 import "../Mintable/Mintable.sol";
 import "../../utils/Ownable/Ownable.sol";
@@ -26,7 +27,7 @@ contract DummyERC20Token is Mintable, Ownable {
     string public symbol;
     uint256 public decimals;
 
-    function DummyERC20Token(
+    constructor (
         string _name,
         string _symbol,
         uint256 _decimals,
diff --git a/packages/contracts/src/contracts/current/test/DummyERC721Token/DummyERC721Token.sol b/packages/contracts/src/contracts/current/test/DummyERC721Token/DummyERC721Token.sol
index 4fbaa6b74..22ebbd3c1 100644
--- a/packages/contracts/src/contracts/current/test/DummyERC721Token/DummyERC721Token.sol
+++ b/packages/contracts/src/contracts/current/test/DummyERC721Token/DummyERC721Token.sol
@@ -16,7 +16,9 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
+pragma experimental ABIEncoderV2;
+
 import "../../tokens/ERC721Token/ERC721Token.sol";
 import "../../utils/Ownable/Ownable.sol";
 
@@ -30,7 +32,7 @@ contract DummyERC721Token is
     * @param name of token
     * @param symbol of token
     */
-    function DummyERC721Token(
+    constructor (
         string name,
         string symbol)
         public
@@ -47,7 +49,10 @@ contract DummyERC721Token is
         public
         onlyOwner
     {
-        require(!exists(tokenId));
+        require(
+            !exists(tokenId),
+            "Token with tokenId already exists."
+        );
         _mint(to, tokenId);
     }
 }
diff --git a/packages/contracts/src/contracts/current/test/Mintable/Mintable.sol b/packages/contracts/src/contracts/current/test/Mintable/Mintable.sol
index 305737b72..fd944f244 100644
--- a/packages/contracts/src/contracts/current/test/Mintable/Mintable.sol
+++ b/packages/contracts/src/contracts/current/test/Mintable/Mintable.sol
@@ -16,7 +16,8 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
+pragma experimental ABIEncoderV2;
 
 import "../../tokens/UnlimitedAllowanceToken/UnlimitedAllowanceToken.sol";
 import "../../utils/SafeMath/SafeMath.sol";
@@ -29,7 +30,10 @@ contract Mintable is UnlimitedAllowanceToken, SafeMath {
     function mint(uint256 _value)
         public
     {
-        require(_value <= 100000000000000000000);
+        require(
+            _value <= 100000000000000000000,
+            "Minting more than 100000000000000000000 is not allowed."
+        );
         balances[msg.sender] = safeAdd(_value, balances[msg.sender]);
         totalSupply = safeAdd(totalSupply, _value);
     }
diff --git a/packages/contracts/src/contracts/current/test/TestAssetProxyDispatcher/TestAssetProxyDispatcher.sol b/packages/contracts/src/contracts/current/test/TestAssetProxyDispatcher/TestAssetProxyDispatcher.sol
index 8206b84bd..93ec3cef3 100644
--- a/packages/contracts/src/contracts/current/test/TestAssetProxyDispatcher/TestAssetProxyDispatcher.sol
+++ b/packages/contracts/src/contracts/current/test/TestAssetProxyDispatcher/TestAssetProxyDispatcher.sol
@@ -16,7 +16,8 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
+pragma experimental ABIEncoderV2;
 
 import "../../protocol/Exchange/MixinAssetProxyDispatcher.sol";
 
diff --git a/packages/contracts/src/contracts/current/test/TestLibBytes/TestLibBytes.sol b/packages/contracts/src/contracts/current/test/TestLibBytes/TestLibBytes.sol
new file mode 100644
index 000000000..1597ff8d5
--- /dev/null
+++ b/packages/contracts/src/contracts/current/test/TestLibBytes/TestLibBytes.sol
@@ -0,0 +1,133 @@
+/*
+
+  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 ^0.4.23;
+pragma experimental ABIEncoderV2;
+
+import "../../utils/LibBytes/LibBytes.sol";
+
+contract TestLibBytes is
+    LibBytes
+{
+
+    /// @dev Tests equality of two byte arrays.
+    /// @param lhs First byte array to compare.
+    /// @param rhs Second byte array to compare.
+    /// @return True if arrays are the same. False otherwise.
+    function publicAreBytesEqual(bytes memory lhs, bytes memory rhs)
+        public
+        pure
+        returns (bool equal)
+    {
+        equal = areBytesEqual(lhs, rhs);
+        return equal;
+    }
+
+    /// @dev Reads an address from a position in a byte array.
+    /// @param b Byte array containing an address.
+    /// @param index Index in byte array of address.
+    /// @return address from byte array.
+    function publicReadAddress(
+        bytes memory b,
+        uint256 index)
+        public
+        pure
+        returns (address result)
+    {
+        result = readAddress(b, index);
+        return result;
+    }
+
+    /// @dev Writes an address into a specific position in a byte array.
+    /// @param b Byte array to insert address into.
+    /// @param index Index in byte array of address.
+    /// @param input Address to put into byte array.
+    function publicWriteAddress(
+        bytes memory b,
+        uint256 index,
+        address input)
+        public
+        pure
+        returns (bytes memory)
+    {
+        writeAddress(b, index, input);
+        return b;
+    }
+
+    /// @dev Reads a bytes32 value from a position in a byte array.
+    /// @param b Byte array containing a bytes32 value.
+    /// @param index Index in byte array of bytes32 value.
+    /// @return bytes32 value from byte array.
+    function publicReadBytes32(
+        bytes memory b,
+        uint256 index)
+        public
+        pure
+        returns (bytes32 result)
+    {
+        result = readBytes32(b, index);
+        return result;
+    }
+
+    /// @dev Writes a bytes32 into a specific position in a byte array.
+    /// @param b Byte array to insert <input> into.
+    /// @param index Index in byte array of <input>.
+    /// @param input bytes32 to put into byte array.
+    function publicWriteBytes32(
+        bytes memory b,
+        uint256 index,
+        bytes32 input)
+        public
+        pure
+        returns (bytes memory)
+    {
+        writeBytes32(b, index, input);
+        return b;
+    }
+
+    /// @dev Reads a uint256 value from a position in a byte array.
+    /// @param b Byte array containing a uint256 value.
+    /// @param index Index in byte array of uint256 value.
+    /// @return uint256 value from byte array.
+    function publicReadUint256(
+        bytes memory b,
+        uint256 index)
+        public
+        pure
+        returns (uint256 result)
+    {
+        result = readUint256(b, index);
+        return result;
+    }
+
+    /// @dev Writes a uint256 into a specific position in a byte array.
+    /// @param b Byte array to insert <input> into.
+    /// @param index Index in byte array of <input>.
+    /// @param input uint256 to put into byte array.
+    function publicWriteUint256(
+        bytes memory b,
+        uint256 index,
+        uint256 input)
+        public
+        pure
+        returns (bytes memory)
+    {
+        writeUint256(b, index, input);
+        return b;
+    }
+}
diff --git a/packages/contracts/src/contracts/current/test/TestLibs/TestLibs.sol b/packages/contracts/src/contracts/current/test/TestLibs/TestLibs.sol
index a5b327a90..0dc7785b2 100644
--- a/packages/contracts/src/contracts/current/test/TestLibs/TestLibs.sol
+++ b/packages/contracts/src/contracts/current/test/TestLibs/TestLibs.sol
@@ -16,12 +16,12 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
 pragma experimental ABIEncoderV2;
 
-import "../../protocol/Exchange/LibMath.sol";
-import "../../protocol/Exchange/LibOrder.sol";
-import "../../protocol/Exchange/LibFillResults.sol";
+import "../../protocol/Exchange/libs/LibMath.sol";
+import "../../protocol/Exchange/libs/LibOrder.sol";
+import "../../protocol/Exchange/libs/LibFillResults.sol";
 
 contract TestLibs is 
     LibMath,
diff --git a/packages/contracts/src/contracts/current/test/TestSignatureValidator/TestSignatureValidator.sol b/packages/contracts/src/contracts/current/test/TestSignatureValidator/TestSignatureValidator.sol
index 4ba04b64e..20202cd7b 100644
--- a/packages/contracts/src/contracts/current/test/TestSignatureValidator/TestSignatureValidator.sol
+++ b/packages/contracts/src/contracts/current/test/TestSignatureValidator/TestSignatureValidator.sol
@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
 pragma experimental ABIEncoderV2;
 
 import "../../protocol/Exchange/MixinSignatureValidator.sol";
diff --git a/packages/contracts/src/contracts/current/tokens/ERC20Token/ERC20Token.sol b/packages/contracts/src/contracts/current/tokens/ERC20Token/ERC20Token.sol
index 13ceeb2c6..6497d3c7a 100644
--- a/packages/contracts/src/contracts/current/tokens/ERC20Token/ERC20Token.sol
+++ b/packages/contracts/src/contracts/current/tokens/ERC20Token/ERC20Token.sol
@@ -16,17 +16,34 @@
 
 */
 
-pragma solidity ^0.4.18;
+pragma solidity ^0.4.23;
+pragma experimental ABIEncoderV2;
 
 import "./IERC20Token.sol";
 
 contract ERC20Token is IERC20Token {
 
+    string constant INSUFFICIENT_BALANCE = "Insufficient balance to complete transfer.";
+    string constant INSUFFICIENT_ALLOWANCE = "Insufficient allowance to complete transfer.";
+    string constant OVERFLOW = "Transfer would result in an overflow.";
+
+    mapping (address => uint256) balances;
+    mapping (address => mapping (address => uint256)) allowed;
+
+    uint256 public totalSupply;
+
     function transfer(address _to, uint256 _value)
         public
         returns (bool)
     {
-        require(balances[msg.sender] >= _value && balances[_to] + _value >= balances[_to]);
+        require(
+            balances[msg.sender] >= _value,
+            INSUFFICIENT_BALANCE
+        );
+        require(
+            balances[_to] + _value >= balances[_to],
+            OVERFLOW
+        );
         balances[msg.sender] -= _value;
         balances[_to] += _value;
         emit Transfer(msg.sender, _to, _value);
@@ -37,7 +54,18 @@ contract ERC20Token is IERC20Token {
         public
         returns (bool)
     {
-        require(balances[_from] >= _value && allowed[_from][msg.sender] >= _value && balances[_to] + _value >= balances[_to]);
+        require(
+            balances[_from] >= _value,
+            INSUFFICIENT_BALANCE
+        );
+        require(
+            allowed[_from][msg.sender] >= _value,
+            INSUFFICIENT_ALLOWANCE
+        );
+        require(
+            balances[_to] + _value >= balances[_to],
+            OVERFLOW
+        );
         balances[_to] += _value;
         balances[_from] -= _value;
         allowed[_from][msg.sender] -= _value;
@@ -68,8 +96,5 @@ contract ERC20Token is IERC20Token {
     {
         return allowed[_owner][_spender];
     }
-
-    mapping (address => uint256) balances;
-    mapping (address => mapping (address => uint256)) allowed;
-    uint256 public totalSupply;
 }
+
diff --git a/packages/contracts/src/contracts/current/tokens/ERC20Token/IERC20Token.sol b/packages/contracts/src/contracts/current/tokens/ERC20Token/IERC20Token.sol
index 0159b31e8..537f5a83d 100644
--- a/packages/contracts/src/contracts/current/tokens/ERC20Token/IERC20Token.sol
+++ b/packages/contracts/src/contracts/current/tokens/ERC20Token/IERC20Token.sol
@@ -16,11 +16,12 @@
 
 */
 
-pragma solidity ^0.4.18;
+pragma solidity ^0.4.23;
+pragma experimental ABIEncoderV2;
 
 contract IERC20Token {
 
-    /// @notice send `_value` token to `_to` from `msg.sender`
+    /// @notice 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
@@ -28,7 +29,7 @@ contract IERC20Token {
         public
         returns (bool);
 
-    /// @notice send `_value` token to `_to` from `_from` on the condition it is approved by `_from`
+    /// @notice 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
@@ -61,10 +62,12 @@ contract IERC20Token {
     event Transfer(
         address indexed _from,
         address indexed _to,
-        uint256 _value);
+        uint256 _value
+    );
     
     event Approval(
         address indexed _owner,
         address indexed _spender,
-        uint256 _value);
+        uint256 _value
+    );
 }
diff --git a/packages/contracts/src/contracts/current/tokens/ERC721Token/ERC721Token.sol b/packages/contracts/src/contracts/current/tokens/ERC721Token/ERC721Token.sol
index 3bf064c3f..b3493bc99 100644
--- a/packages/contracts/src/contracts/current/tokens/ERC721Token/ERC721Token.sol
+++ b/packages/contracts/src/contracts/current/tokens/ERC721Token/ERC721Token.sol
@@ -23,7 +23,7 @@ TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
 
 import "./IERC721Token.sol";
 import "./IERC721Receiver.sol";
diff --git a/packages/contracts/src/contracts/current/tokens/ERC721Token/IERC721Receiver.sol b/packages/contracts/src/contracts/current/tokens/ERC721Token/IERC721Receiver.sol
index 26871cc89..3484bf824 100644
--- a/packages/contracts/src/contracts/current/tokens/ERC721Token/IERC721Receiver.sol
+++ b/packages/contracts/src/contracts/current/tokens/ERC721Token/IERC721Receiver.sol
@@ -23,7 +23,7 @@ TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
 
 /**
  * @title ERC721 token receiver interface
diff --git a/packages/contracts/src/contracts/current/tokens/ERC721Token/IERC721Token.sol b/packages/contracts/src/contracts/current/tokens/ERC721Token/IERC721Token.sol
index 73741ed53..81e1b97af 100644
--- a/packages/contracts/src/contracts/current/tokens/ERC721Token/IERC721Token.sol
+++ b/packages/contracts/src/contracts/current/tokens/ERC721Token/IERC721Token.sol
@@ -23,7 +23,7 @@ TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
 
 /**
  * @title ERC721 Non-Fungible Token Standard basic interface
diff --git a/packages/contracts/src/contracts/current/tokens/UnlimitedAllowanceToken/UnlimitedAllowanceToken.sol b/packages/contracts/src/contracts/current/tokens/UnlimitedAllowanceToken/UnlimitedAllowanceToken.sol
index be774e374..395e5d356 100644
--- a/packages/contracts/src/contracts/current/tokens/UnlimitedAllowanceToken/UnlimitedAllowanceToken.sol
+++ b/packages/contracts/src/contracts/current/tokens/UnlimitedAllowanceToken/UnlimitedAllowanceToken.sol
@@ -16,9 +16,10 @@
 
 */
 
-pragma solidity ^0.4.18;
+pragma solidity ^0.4.23;
+pragma experimental ABIEncoderV2;
 
-import { ERC20Token } from "../ERC20Token/ERC20Token.sol";
+import "../ERC20Token/ERC20Token.sol";
 
 contract UnlimitedAllowanceToken is ERC20Token {
 
@@ -34,7 +35,18 @@ contract UnlimitedAllowanceToken is ERC20Token {
         returns (bool)
     {
         uint256 allowance = allowed[_from][msg.sender];
-        require(balances[_from] >= _value && allowance >= _value && balances[_to] + _value >= balances[_to]);
+        require(
+            balances[_from] >= _value,
+            INSUFFICIENT_BALANCE
+        );
+        require(
+            allowance >= _value,
+            INSUFFICIENT_ALLOWANCE
+        );
+        require(
+            balances[_to] + _value >= balances[_to],
+            OVERFLOW
+        );
         balances[_to] += _value;
         balances[_from] -= _value;
         if (allowance < MAX_UINT) {
diff --git a/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol b/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol
index ce107f306..3c5531e35 100644
--- a/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol
+++ b/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol
@@ -16,16 +16,21 @@
 
 */
 
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
 
 contract LibBytes {
 
+    // Revert reasons
+    string constant GTE_20_LENGTH_REQUIRED = "Length must be greater than or equal to 20.";
+    string constant GTE_32_LENGTH_REQUIRED = "Length must be greater than or equal to 32.";
+
     /// @dev Tests equality of two byte arrays.
     /// @param lhs First byte array to compare.
     /// @param rhs Second byte array to compare.
     /// @return True if arrays are the same. False otherwise.
     function areBytesEqual(bytes memory lhs, bytes memory rhs)
-        public pure
+        internal
+        pure
         returns (bool equal)
     {
         assembly {
@@ -58,10 +63,14 @@ contract LibBytes {
     function readAddress(
         bytes memory b,
         uint256 index)
-        public pure
+        internal
+        pure
         returns (address result)
     {
-        require(b.length >= index + 20); // 20 is length of address
+        require(
+            b.length >= index + 20,  // 20 is length of address
+            GTE_20_LENGTH_REQUIRED
+        ); 
 
         // Add offset to index:
         // 1. Arrays are prefixed by 32-byte length parameter (add 32 to index)
@@ -86,9 +95,13 @@ contract LibBytes {
         bytes memory b,
         uint256 index,
         address input)
-        public pure
+        internal
+        pure
     {
-        require(b.length >= index + 20); // 20 is length of address
+        require(
+            b.length >= index + 20,  // 20 is length of address
+            GTE_20_LENGTH_REQUIRED
+        ); 
 
         // Add offset to index:
         // 1. Arrays are prefixed by 32-byte length parameter (add 32 to index)
@@ -119,10 +132,14 @@ contract LibBytes {
     function readBytes32(
         bytes memory b,
         uint256 index)
-        public pure
+        internal
+        pure
         returns (bytes32 result)
     {
-        require(b.length >= index + 32);
+        require(
+            b.length >= index + 32,
+            GTE_32_LENGTH_REQUIRED
+        );
 
         // Arrays are prefixed by a 256 bit length parameter
         index += 32;
@@ -142,9 +159,13 @@ contract LibBytes {
         bytes memory b,
         uint256 index,
         bytes32 input)
-        public pure
+        internal
+        pure
     {
-        require(b.length >= index + 32);
+        require(
+            b.length >= index + 32,
+            GTE_32_LENGTH_REQUIRED
+        );
 
         // Arrays are prefixed by a 256 bit length parameter
         index += 32;
@@ -162,7 +183,8 @@ contract LibBytes {
     function readUint256(
         bytes memory b,
         uint256 index)
-        public pure
+        internal
+        pure
         returns (uint256 result)
     {
         return uint256(readBytes32(b, index));
@@ -176,7 +198,8 @@ contract LibBytes {
         bytes memory b,
         uint256 index,
         uint256 input)
-        public pure
+        internal
+        pure
     {
         writeBytes32(b, index, bytes32(input));
     }
diff --git a/packages/contracts/src/contracts/current/utils/Ownable/IOwnable.sol b/packages/contracts/src/contracts/current/utils/Ownable/IOwnable.sol
index 7784a7ba9..63b04945f 100644
--- a/packages/contracts/src/contracts/current/utils/Ownable/IOwnable.sol
+++ b/packages/contracts/src/contracts/current/utils/Ownable/IOwnable.sol
@@ -1,4 +1,5 @@
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
+pragma experimental ABIEncoderV2;
 
 /*
  * Ownable
diff --git a/packages/contracts/src/contracts/current/utils/Ownable/Ownable.sol b/packages/contracts/src/contracts/current/utils/Ownable/Ownable.sol
index 91a5cb7ae..933aa168a 100644
--- a/packages/contracts/src/contracts/current/utils/Ownable/Ownable.sol
+++ b/packages/contracts/src/contracts/current/utils/Ownable/Ownable.sol
@@ -1,4 +1,5 @@
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
+pragma experimental ABIEncoderV2;
 
 /*
  * Ownable
@@ -7,19 +8,22 @@ pragma solidity ^0.4.21;
  * Provides onlyOwner modifier, which prevents function from running if it is called by anyone other than the owner.
  */
 
-import "../Ownable/IOwnable.sol";
+import "./IOwnable.sol";
 
 contract Ownable is IOwnable {
     address public owner;
 
-    function Ownable()
+    constructor ()
         public
     {
         owner = msg.sender;
     }
 
     modifier onlyOwner() {
-        require(msg.sender == owner);
+        require(
+            msg.sender == owner,
+            "Only contract owner is allowed to call this method."
+        );
         _;
     }
 
diff --git a/packages/contracts/src/contracts/current/utils/SafeMath/SafeMath.sol b/packages/contracts/src/contracts/current/utils/SafeMath/SafeMath.sol
index 7bd9c2122..1ab27eebc 100644
--- a/packages/contracts/src/contracts/current/utils/SafeMath/SafeMath.sol
+++ b/packages/contracts/src/contracts/current/utils/SafeMath/SafeMath.sol
@@ -1,4 +1,5 @@
-pragma solidity ^0.4.21;
+pragma solidity ^0.4.23;
+pragma experimental ABIEncoderV2;
 
 contract SafeMath {
     function safeMul(uint a, uint b)
diff --git a/packages/contracts/src/utils/types.ts b/packages/contracts/src/utils/types.ts
index 6f9aeda94..2200e09f3 100644
--- a/packages/contracts/src/utils/types.ts
+++ b/packages/contracts/src/utils/types.ts
@@ -99,7 +99,7 @@ export enum ContractName {
     ERC20Proxy = 'ERC20Proxy',
     ERC721Proxy = 'ERC721Proxy',
     DummyERC721Token = 'DummyERC721Token',
-    LibBytes = 'LibBytes',
+    TestLibBytes = 'TestLibBytes',
     Authorizable = 'Authorizable',
 }