core, consensus: pluggable consensus engines (#3817)

This commit adds pluggable consensus engines to go-ethereum. In short, it
introduces a generic consensus interface, and refactors the entire codebase to
use this interface.

16 files changed, 335 insertions, 962 deletions

diff --git a/core/bench_test.go b/core/bench_test.go
index a154ccbb1..20676fc97 100644
--- a/core/bench_test.go
+++ b/core/bench_test.go
@@ -25,13 +25,13 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/math"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 func BenchmarkInsertChain_empty_memdb(b *testing.B) {
@@ -176,7 +176,7 @@ func benchInsertChain(b *testing.B, disk bool, gen func(int, *BlockGen)) {
 	// Time the insertion of the new chain.
 	// State and blocks are stored in the same DB.
 	evmux := new(event.TypeMux)
-	chainman, _ := NewBlockChain(db, gspec.Config, pow.FakePow{}, evmux, vm.Config{})
+	chainman, _ := NewBlockChain(db, gspec.Config, ethash.NewFaker(), evmux, vm.Config{})
 	defer chainman.Stop()
 	b.ReportAllocs()
 	b.ResetTimer()
@@ -286,7 +286,7 @@ func benchReadChain(b *testing.B, full bool, count uint64) {
 		if err != nil {
 			b.Fatalf("error opening database at %v: %v", dir, err)
 		}
-		chain, err := NewBlockChain(db, params.TestChainConfig, pow.FakePow{}, new(event.TypeMux), vm.Config{})
+		chain, err := NewBlockChain(db, params.TestChainConfig, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 		if err != nil {
 			b.Fatalf("error creating chain: %v", err)
 		}
diff --git a/core/block_validator.go b/core/block_validator.go
index f93a9f40b..00457dd7a 100644
--- a/core/block_validator.go
+++ b/core/block_validator.go
@@ -19,22 +19,12 @@ package core
 import (
 	"fmt"
 	"math/big"
-	"time"
 
-	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/math"
+	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
-	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
-	"gopkg.in/fatih/set.v0"
-)
-
-var (
-	ExpDiffPeriod = big.NewInt(100000)
-	big10         = big.NewInt(10)
-	bigMinus99    = big.NewInt(-99)
 )
 
 // BlockValidator is responsible for validating block headers, uncles and
@@ -44,30 +34,24 @@ var (
 type BlockValidator struct {
 	config *params.ChainConfig // Chain configuration options
 	bc     *BlockChain         // Canonical block chain
-	Pow    pow.PoW             // Proof of work used for validating
+	engine consensus.Engine    // Consensus engine used for validating
 }
 
 // NewBlockValidator returns a new block validator which is safe for re-use
-func NewBlockValidator(config *params.ChainConfig, blockchain *BlockChain, pow pow.PoW) *BlockValidator {
+func NewBlockValidator(config *params.ChainConfig, blockchain *BlockChain, engine consensus.Engine) *BlockValidator {
 	validator := &BlockValidator{
 		config: config,
-		Pow:    pow,
+		engine: engine,
 		bc:     blockchain,
 	}
 	return validator
 }
 
-// ValidateBlock validates the given block's header and uncles and verifies the
-// the block header's transaction and uncle roots.
-//
-// ValidateBlock does not validate the header's pow. The pow work validated
-// separately so we can process them in parallel.
-//
-// ValidateBlock also validates and makes sure that any previous state (or present)
-// state that might or might not be present is checked to make sure that fast
-// sync has done it's job proper. This prevents the block validator from accepting
-// false positives where a header is present but the state is not.
-func (v *BlockValidator) ValidateBlock(block *types.Block) error {
+// ValidateBody validates the given block's uncles and verifies the the block
+// header's transaction and uncle roots. The headers are assumed to be already
+// validated at this point.
+func (v *BlockValidator) ValidateBody(block *types.Block) error {
+	// Check whether the block's known, and if not, that it's linkable
 	if v.bc.HasBlock(block.Hash()) {
 		if _, err := state.New(block.Root(), v.bc.chainDb); err == nil {
 			return &KnownBlockError{block.Number(), block.Hash()}
@@ -80,30 +64,17 @@ func (v *BlockValidator) ValidateBlock(block *types.Block) error {
 	if _, err := state.New(parent.Root(), v.bc.chainDb); err != nil {
 		return ParentError(block.ParentHash())
 	}
-
+	// Header validity is known at this point, check the uncles and transactions
 	header := block.Header()
-	// validate the block header
-	if err := ValidateHeader(v.config, v.Pow, header, parent.Header(), false, false); err != nil {
+	if err := v.engine.VerifyUncles(v.bc, block); err != nil {
 		return err
 	}
-	// verify the uncles are correctly rewarded
-	if err := v.VerifyUncles(block, parent); err != nil {
-		return err
+	if hash := types.CalcUncleHash(block.Uncles()); hash != header.UncleHash {
+		return fmt.Errorf("uncle root hash mismatch: have %x, want %x", hash, header.UncleHash)
 	}
-
-	// Verify UncleHash before running other uncle validations
-	unclesSha := types.CalcUncleHash(block.Uncles())
-	if unclesSha != header.UncleHash {
-		return fmt.Errorf("invalid uncles root hash (remote: %x local: %x)", header.UncleHash, unclesSha)
-	}
-
-	// The transactions Trie's root (R = (Tr [[i, RLP(T1)], [i, RLP(T2)], ... [n, RLP(Tn)]]))
-	// can be used by light clients to make sure they've received the correct Txs
-	txSha := types.DeriveSha(block.Transactions())
-	if txSha != header.TxHash {
-		return fmt.Errorf("invalid transaction root hash (remote: %x local: %x)", header.TxHash, txSha)
+	if hash := types.DeriveSha(block.Transactions()); hash != header.TxHash {
+		return fmt.Errorf("transaction root hash mismatch: have %x, want %x", hash, header.TxHash)
 	}
-
 	return nil
 }
 
@@ -135,222 +106,6 @@ func (v *BlockValidator) ValidateState(block, parent *types.Block, statedb *stat
 	return nil
 }
 
-// VerifyUncles verifies the given block's uncles and applies the Ethereum
-// consensus rules to the various block headers included; it will return an
-// error if any of the included uncle headers were invalid. It returns an error
-// if the validation failed.
-func (v *BlockValidator) VerifyUncles(block, parent *types.Block) error {
-	// validate that there are at most 2 uncles included in this block
-	if len(block.Uncles()) > 2 {
-		return ValidationError("Block can only contain maximum 2 uncles (contained %v)", len(block.Uncles()))
-	}
-
-	uncles := set.New()
-	ancestors := make(map[common.Hash]*types.Block)
-	for _, ancestor := range v.bc.GetBlocksFromHash(block.ParentHash(), 7) {
-		ancestors[ancestor.Hash()] = ancestor
-		// Include ancestors uncles in the uncle set. Uncles must be unique.
-		for _, uncle := range ancestor.Uncles() {
-			uncles.Add(uncle.Hash())
-		}
-	}
-	ancestors[block.Hash()] = block
-	uncles.Add(block.Hash())
-
-	for i, uncle := range block.Uncles() {
-		hash := uncle.Hash()
-		if uncles.Has(hash) {
-			// Error not unique
-			return UncleError("uncle[%d](%x) not unique", i, hash[:4])
-		}
-		uncles.Add(hash)
-
-		if ancestors[hash] != nil {
-			branch := fmt.Sprintf("  O - %x\n  |\n", block.Hash())
-			for h := range ancestors {
-				branch += fmt.Sprintf("  O - %x\n  |\n", h)
-			}
-			log.Warn(branch)
-			return UncleError("uncle[%d](%x) is ancestor", i, hash[:4])
-		}
-
-		if ancestors[uncle.ParentHash] == nil || uncle.ParentHash == parent.Hash() {
-			return UncleError("uncle[%d](%x)'s parent is not ancestor (%x)", i, hash[:4], uncle.ParentHash[0:4])
-		}
-
-		if err := ValidateHeader(v.config, v.Pow, uncle, ancestors[uncle.ParentHash].Header(), true, true); err != nil {
-			return ValidationError(fmt.Sprintf("uncle[%d](%x) header invalid: %v", i, hash[:4], err))
-		}
-	}
-
-	return nil
-}
-
-// ValidateHeader validates the given header and, depending on the pow arg,
-// checks the proof of work of the given header. Returns an error if the
-// validation failed.
-func (v *BlockValidator) ValidateHeader(header, parent *types.Header, checkPow bool) error {
-	// Short circuit if the parent is missing.
-	if parent == nil {
-		return ParentError(header.ParentHash)
-	}
-	// Short circuit if the header's already known or its parent is missing
-	if v.bc.HasHeader(header.Hash()) {
-		return nil
-	}
-	return ValidateHeader(v.config, v.Pow, header, parent, checkPow, false)
-}
-
-// Validates a header. Returns an error if the header is invalid.
-//
-// See YP section 4.3.4. "Block Header Validity"
-func ValidateHeader(config *params.ChainConfig, pow pow.PoW, header *types.Header, parent *types.Header, checkPow, uncle bool) error {
-	if uint64(len(header.Extra)) > params.MaximumExtraDataSize {
-		return fmt.Errorf("Header extra data too long (%d)", len(header.Extra))
-	}
-
-	if uncle {
-		if header.Time.Cmp(math.MaxBig256) == 1 {
-			return BlockTSTooBigErr
-		}
-	} else {
-		if header.Time.Cmp(big.NewInt(time.Now().Unix())) == 1 {
-			return BlockFutureErr
-		}
-	}
-	if header.Time.Cmp(parent.Time) != 1 {
-		return BlockEqualTSErr
-	}
-
-	expd := CalcDifficulty(config, header.Time.Uint64(), parent.Time.Uint64(), parent.Number, parent.Difficulty)
-	if expd.Cmp(header.Difficulty) != 0 {
-		return fmt.Errorf("Difficulty check failed for header (remote: %v local: %v)", header.Difficulty, expd)
-	}
-
-	a := new(big.Int).Set(parent.GasLimit)
-	a = a.Sub(a, header.GasLimit)
-	a.Abs(a)
-	b := new(big.Int).Set(parent.GasLimit)
-	b = b.Div(b, params.GasLimitBoundDivisor)
-	if !(a.Cmp(b) < 0) || (header.GasLimit.Cmp(params.MinGasLimit) == -1) {
-		return fmt.Errorf("GasLimit check failed for header (remote: %v local_max: %v)", header.GasLimit, b)
-	}
-
-	num := new(big.Int).Set(parent.Number)
-	num.Sub(header.Number, num)
-	if num.Cmp(big.NewInt(1)) != 0 {
-		return BlockNumberErr
-	}
-
-	if checkPow {
-		// Verify the nonce of the header. Return an error if it's not valid
-		if err := pow.Verify(types.NewBlockWithHeader(header)); err != nil {
-			return &BlockNonceErr{header.Number, header.Hash(), header.Nonce.Uint64()}
-		}
-	}
-	// If all checks passed, validate the extra-data field for hard forks
-	if err := ValidateDAOHeaderExtraData(config, header); err != nil {
-		return err
-	}
-	if !uncle && config.EIP150Block != nil && config.EIP150Block.Cmp(header.Number) == 0 {
-		if config.EIP150Hash != (common.Hash{}) && config.EIP150Hash != header.Hash() {
-			return ValidationError("Homestead gas reprice fork hash mismatch: have 0x%x, want 0x%x", header.Hash(), config.EIP150Hash)
-		}
-	}
-	return nil
-}
-
-// CalcDifficulty is the difficulty adjustment algorithm. It returns
-// the difficulty that a new block should have when created at time
-// given the parent block's time and difficulty.
-func CalcDifficulty(config *params.ChainConfig, time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
-	if config.IsHomestead(new(big.Int).Add(parentNumber, common.Big1)) {
-		return calcDifficultyHomestead(time, parentTime, parentNumber, parentDiff)
-	} else {
-		return calcDifficultyFrontier(time, parentTime, parentNumber, parentDiff)
-	}
-}
-
-func calcDifficultyHomestead(time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
-	// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-2.mediawiki
-	// algorithm:
-	// diff = (parent_diff +
-	//         (parent_diff / 2048 * max(1 - (block_timestamp - parent_timestamp) // 10, -99))
-	//        ) + 2^(periodCount - 2)
-
-	bigTime := new(big.Int).SetUint64(time)
-	bigParentTime := new(big.Int).SetUint64(parentTime)
-
-	// holds intermediate values to make the algo easier to read & audit
-	x := new(big.Int)
-	y := new(big.Int)
-
-	// 1 - (block_timestamp -parent_timestamp) // 10
-	x.Sub(bigTime, bigParentTime)
-	x.Div(x, big10)
-	x.Sub(common.Big1, x)
-
-	// max(1 - (block_timestamp - parent_timestamp) // 10, -99)))
-	if x.Cmp(bigMinus99) < 0 {
-		x.Set(bigMinus99)
-	}
-
-	// (parent_diff + parent_diff // 2048 * max(1 - (block_timestamp - parent_timestamp) // 10, -99))
-	y.Div(parentDiff, params.DifficultyBoundDivisor)
-	x.Mul(y, x)
-	x.Add(parentDiff, x)
-
-	// minimum difficulty can ever be (before exponential factor)
-	if x.Cmp(params.MinimumDifficulty) < 0 {
-		x.Set(params.MinimumDifficulty)
-	}
-
-	// for the exponential factor
-	periodCount := new(big.Int).Add(parentNumber, common.Big1)
-	periodCount.Div(periodCount, ExpDiffPeriod)
-
-	// the exponential factor, commonly referred to as "the bomb"
-	// diff = diff + 2^(periodCount - 2)
-	if periodCount.Cmp(common.Big1) > 0 {
-		y.Sub(periodCount, common.Big2)
-		y.Exp(common.Big2, y, nil)
-		x.Add(x, y)
-	}
-
-	return x
-}
-
-func calcDifficultyFrontier(time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
-	diff := new(big.Int)
-	adjust := new(big.Int).Div(parentDiff, params.DifficultyBoundDivisor)
-	bigTime := new(big.Int)
-	bigParentTime := new(big.Int)
-
-	bigTime.SetUint64(time)
-	bigParentTime.SetUint64(parentTime)
-
-	if bigTime.Sub(bigTime, bigParentTime).Cmp(params.DurationLimit) < 0 {
-		diff.Add(parentDiff, adjust)
-	} else {
-		diff.Sub(parentDiff, adjust)
-	}
-	if diff.Cmp(params.MinimumDifficulty) < 0 {
-		diff.Set(params.MinimumDifficulty)
-	}
-
-	periodCount := new(big.Int).Add(parentNumber, common.Big1)
-	periodCount.Div(periodCount, ExpDiffPeriod)
-	if periodCount.Cmp(common.Big1) > 0 {
-		// diff = diff + 2^(periodCount - 2)
-		expDiff := periodCount.Sub(periodCount, common.Big2)
-		expDiff.Exp(common.Big2, expDiff, nil)
-		diff.Add(diff, expDiff)
-		diff = math.BigMax(diff, params.MinimumDifficulty)
-	}
-
-	return diff
-}
-
 // CalcGasLimit computes the gas limit of the next block after parent.
 // The result may be modified by the caller.
 // This is miner strategy, not consensus protocol.
diff --git a/core/block_validator_test.go b/core/block_validator_test.go
index a07dd9e51..abe1766b4 100644
--- a/core/block_validator_test.go
+++ b/core/block_validator_test.go
@@ -17,64 +17,179 @@
 package core
 
 import (
-	"math/big"
+	"runtime"
 	"testing"
+	"time"
 
-	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/ethdb"
+	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
-func testGenesis(account common.Address, balance *big.Int) *Genesis {
-	return &Genesis{
-		Config: params.TestChainConfig,
-		Alloc:  GenesisAlloc{account: {Balance: balance}},
+// Tests that simple header verification works, for both good and bad blocks.
+func TestHeaderVerification(t *testing.T) {
+	// Create a simple chain to verify
+	var (
+		testdb, _ = ethdb.NewMemDatabase()
+		gspec     = &Genesis{Config: params.TestChainConfig}
+		genesis   = gspec.MustCommit(testdb)
+		blocks, _ = GenerateChain(params.TestChainConfig, genesis, testdb, 8, nil)
+	)
+	headers := make([]*types.Header, len(blocks))
+	for i, block := range blocks {
+		headers[i] = block.Header()
+	}
+	// Run the header checker for blocks one-by-one, checking for both valid and invalid nonces
+	chain, _ := NewBlockChain(testdb, params.TestChainConfig, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
+
+	for i := 0; i < len(blocks); i++ {
+		for j, valid := range []bool{true, false} {
+			var results <-chan error
+
+			if valid {
+				engine := ethash.NewFaker()
+				_, results = engine.VerifyHeaders(chain, []*types.Header{headers[i]}, []bool{true})
+			} else {
+				engine := ethash.NewFakeFailer(headers[i].Number.Uint64())
+				_, results = engine.VerifyHeaders(chain, []*types.Header{headers[i]}, []bool{true})
+			}
+			// Wait for the verification result
+			select {
+			case result := <-results:
+				if (result == nil) != valid {
+					t.Errorf("test %d.%d: validity mismatch: have %v, want %v", i, j, result, valid)
+				}
+			case <-time.After(time.Second):
+				t.Fatalf("test %d.%d: verification timeout", i, j)
+			}
+			// Make sure no more data is returned
+			select {
+			case result := <-results:
+				t.Fatalf("test %d.%d: unexpected result returned: %v", i, j, result)
+			case <-time.After(25 * time.Millisecond):
+			}
+		}
+		chain.InsertChain(blocks[i : i+1])
 	}
 }
 
-func TestNumber(t *testing.T) {
-	chain := newTestBlockChain()
-	statedb, _ := state.New(chain.Genesis().Root(), chain.chainDb)
-	header := makeHeader(chain.config, chain.Genesis(), statedb)
-	header.Number = big.NewInt(3)
-	err := ValidateHeader(chain.config, pow.FakePow{}, header, chain.Genesis().Header(), false, false)
-	if err != BlockNumberErr {
-		t.Errorf("expected block number error, got %q", err)
+// Tests that concurrent header verification works, for both good and bad blocks.
+func TestHeaderConcurrentVerification2(t *testing.T)  { testHeaderConcurrentVerification(t, 2) }
+func TestHeaderConcurrentVerification8(t *testing.T)  { testHeaderConcurrentVerification(t, 8) }
+func TestHeaderConcurrentVerification32(t *testing.T) { testHeaderConcurrentVerification(t, 32) }
+
+func testHeaderConcurrentVerification(t *testing.T, threads int) {
+	// Create a simple chain to verify
+	var (
+		testdb, _ = ethdb.NewMemDatabase()
+		gspec     = &Genesis{Config: params.TestChainConfig}
+		genesis   = gspec.MustCommit(testdb)
+		blocks, _ = GenerateChain(params.TestChainConfig, genesis, testdb, 8, nil)
+	)
+	headers := make([]*types.Header, len(blocks))
+	seals := make([]bool, len(blocks))
+
+	for i, block := range blocks {
+		headers[i] = block.Header()
+		seals[i] = true
 	}
+	// Set the number of threads to verify on
+	old := runtime.GOMAXPROCS(threads)
+	defer runtime.GOMAXPROCS(old)
+
+	// Run the header checker for the entire block chain at once both for a valid and
+	// also an invalid chain (enough if one arbitrary block is invalid).
+	for i, valid := range []bool{true, false} {
+		var results <-chan error
+
+		if valid {
+			chain, _ := NewBlockChain(testdb, params.TestChainConfig, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
+			_, results = chain.engine.VerifyHeaders(chain, headers, seals)
+		} else {
+			chain, _ := NewBlockChain(testdb, params.TestChainConfig, ethash.NewFakeFailer(uint64(len(headers)-1)), new(event.TypeMux), vm.Config{})
+			_, results = chain.engine.VerifyHeaders(chain, headers, seals)
+		}
+		// Wait for all the verification results
+		checks := make(map[int]error)
+		for j := 0; j < len(blocks); j++ {
+			select {
+			case result := <-results:
+				checks[j] = result
 
-	header = makeHeader(chain.config, chain.Genesis(), statedb)
-	err = ValidateHeader(chain.config, pow.FakePow{}, header, chain.Genesis().Header(), false, false)
-	if err == BlockNumberErr {
-		t.Errorf("didn't expect block number error")
+			case <-time.After(time.Second):
+				t.Fatalf("test %d.%d: verification timeout", i, j)
+			}
+		}
+		// Check nonce check validity
+		for j := 0; j < len(blocks); j++ {
+			want := valid || (j < len(blocks)-2) // We chose the last-but-one nonce in the chain to fail
+			if (checks[j] == nil) != want {
+				t.Errorf("test %d.%d: validity mismatch: have %v, want %v", i, j, checks[j], want)
+			}
+			if !want {
+				// A few blocks after the first error may pass verification due to concurrent
+				// workers. We don't care about those in this test, just that the correct block
+				// errors out.
+				break
+			}
+		}
+		// Make sure no more data is returned
+		select {
+		case result := <-results:
+			t.Fatalf("test %d: unexpected result returned: %v", i, result)
+		case <-time.After(25 * time.Millisecond):
+		}
 	}
 }
 
-func TestPutReceipt(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
-
-	var addr common.Address
-	addr[0] = 1
-	var hash common.Hash
-	hash[0] = 2
-
-	receipt := new(types.Receipt)
-	receipt.Logs = []*types.Log{{
-		Address:     addr,
-		Topics:      []common.Hash{hash},
-		Data:        []byte("hi"),
-		BlockNumber: 42,
-		TxHash:      hash,
-		TxIndex:     0,
-		BlockHash:   hash,
-		Index:       0,
-	}}
-
-	WriteReceipts(db, types.Receipts{receipt})
-	receipt = GetReceipt(db, common.Hash{})
-	if receipt == nil {
-		t.Error("expected to get 1 receipt, got none.")
+// Tests that aborting a header validation indeed prevents further checks from being
+// run, as well as checks that no left-over goroutines are leaked.
+func TestHeaderConcurrentAbortion2(t *testing.T)  { testHeaderConcurrentAbortion(t, 2) }
+func TestHeaderConcurrentAbortion8(t *testing.T)  { testHeaderConcurrentAbortion(t, 8) }
+func TestHeaderConcurrentAbortion32(t *testing.T) { testHeaderConcurrentAbortion(t, 32) }
+
+func testHeaderConcurrentAbortion(t *testing.T, threads int) {
+	// Create a simple chain to verify
+	var (
+		testdb, _ = ethdb.NewMemDatabase()
+		gspec     = &Genesis{Config: params.TestChainConfig}
+		genesis   = gspec.MustCommit(testdb)
+		blocks, _ = GenerateChain(params.TestChainConfig, genesis, testdb, 1024, nil)
+	)
+	headers := make([]*types.Header, len(blocks))
+	seals := make([]bool, len(blocks))
+
+	for i, block := range blocks {
+		headers[i] = block.Header()
+		seals[i] = true
+	}
+	// Set the number of threads to verify on
+	old := runtime.GOMAXPROCS(threads)
+	defer runtime.GOMAXPROCS(old)
+
+	// Start the verifications and immediately abort
+	chain, _ := NewBlockChain(testdb, params.TestChainConfig, ethash.NewFakeDelayer(time.Millisecond), new(event.TypeMux), vm.Config{})
+	abort, results := chain.engine.VerifyHeaders(chain, headers, seals)
+	close(abort)
+
+	// Deplete the results channel
+	verified := 0
+	for depleted := false; !depleted; {
+		select {
+		case result := <-results:
+			if result != nil {
+				t.Errorf("header %d: validation failed: %v", verified, result)
+			}
+			verified++
+		case <-time.After(50 * time.Millisecond):
+			depleted = true
+		}
+	}
+	// Check that abortion was honored by not processing too many POWs
+	if verified > 2*threads {
+		t.Errorf("verification count too large: have %d, want below %d", verified, 2*threads)
 	}
 }
diff --git a/core/blockchain.go b/core/blockchain.go
index a57832df0..4793431d8 100644
--- a/core/blockchain.go
+++ b/core/blockchain.go
@@ -30,6 +30,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/mclock"
+	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
@@ -39,7 +40,6 @@ import (
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/metrics"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/trie"
 	"github.com/hashicorp/golang-lru"
@@ -104,7 +104,7 @@ type BlockChain struct {
 	procInterrupt int32          // interrupt signaler for block processing
 	wg            sync.WaitGroup // chain processing wait group for shutting down
 
-	pow       pow.PoW
+	engine    consensus.Engine
 	processor Processor // block processor interface
 	validator Validator // block and state validator interface
 	vmConfig  vm.Config
@@ -115,7 +115,7 @@ type BlockChain struct {
 // NewBlockChain returns a fully initialised block chain using information
 // available in the database. It initialiser the default Ethereum Validator and
 // Processor.
-func NewBlockChain(chainDb ethdb.Database, config *params.ChainConfig, pow pow.PoW, mux *event.TypeMux, vmConfig vm.Config) (*BlockChain, error) {
+func NewBlockChain(chainDb ethdb.Database, config *params.ChainConfig, engine consensus.Engine, mux *event.TypeMux, vmConfig vm.Config) (*BlockChain, error) {
 	bodyCache, _ := lru.New(bodyCacheLimit)
 	bodyRLPCache, _ := lru.New(bodyCacheLimit)
 	blockCache, _ := lru.New(blockCacheLimit)
@@ -131,25 +131,22 @@ func NewBlockChain(chainDb ethdb.Database, config *params.ChainConfig, pow pow.P
 		bodyRLPCache: bodyRLPCache,
 		blockCache:   blockCache,
 		futureBlocks: futureBlocks,
-		pow:          pow,
+		engine:       engine,
 		vmConfig:     vmConfig,
 		badBlocks:    badBlocks,
 	}
-	bc.SetValidator(NewBlockValidator(config, bc, pow))
-	bc.SetProcessor(NewStateProcessor(config, bc))
+	bc.SetValidator(NewBlockValidator(config, bc, engine))
+	bc.SetProcessor(NewStateProcessor(config, bc, engine))
 
-	gv := func() HeaderValidator { return bc.Validator() }
 	var err error
-	bc.hc, err = NewHeaderChain(chainDb, config, gv, bc.getProcInterrupt)
+	bc.hc, err = NewHeaderChain(chainDb, config, engine, bc.getProcInterrupt)
 	if err != nil {
 		return nil, err
 	}
-
 	bc.genesisBlock = bc.GetBlockByNumber(0)
 	if bc.genesisBlock == nil {
 		return nil, ErrNoGenesis
 	}
-
 	if err := bc.loadLastState(); err != nil {
 		return nil, err
 	}
@@ -233,9 +230,6 @@ func (self *BlockChain) loadLastState() error {
 	log.Info("Loaded most recent local full block", "number", self.currentBlock.Number(), "hash", self.currentBlock.Hash(), "td", blockTd)
 	log.Info("Loaded most recent local fast block", "number", self.currentFastBlock.Number(), "hash", self.currentFastBlock.Hash(), "td", fastTd)
 
-	// Try to be smart and issue a pow verification for the head to pre-generate caches
-	go self.pow.Verify(types.NewBlockWithHeader(currentHeader))
-
 	return nil
 }
 
@@ -383,9 +377,6 @@ func (self *BlockChain) Processor() Processor {
 	return self.processor
 }
 
-// AuxValidator returns the auxiliary validator (Proof of work atm)
-func (self *BlockChain) AuxValidator() pow.PoW { return self.pow }
-
 // State returns a new mutable state based on the current HEAD block.
 func (self *BlockChain) State() (*state.StateDB, error) {
 	return self.StateAt(self.CurrentBlock().Root())
@@ -906,38 +897,38 @@ func (self *BlockChain) InsertChain(chain types.Blocks) (int, error) {
 		stats         = insertStats{startTime: mclock.Now()}
 		events        = make([]interface{}, 0, len(chain))
 		coalescedLogs []*types.Log
-		nonceChecked  = make([]bool, len(chain))
 	)
+	// Start the parallel header verifier
+	headers := make([]*types.Header, len(chain))
+	seals := make([]bool, len(chain))
 
-	// Start the parallel nonce verifier.
-	nonceAbort, nonceResults := verifyNoncesFromBlocks(self.pow, chain)
-	defer close(nonceAbort)
+	for i, block := range chain {
+		headers[i] = block.Header()
+		seals[i] = true
+	}
+	abort, results := self.engine.VerifyHeaders(self, headers, seals)
+	defer close(abort)
 
+	// Iterate over the blocks and insert when the verifier permits
 	for i, block := range chain {
+		// If the chain is terminating, stop processing blocks
 		if atomic.LoadInt32(&self.procInterrupt) == 1 {
 			log.Debug("Premature abort during blocks processing")
 			break
 		}
-		bstart := time.Now()
-		// Wait for block i's nonce to be verified before processing
-		// its state transition.
-		for !nonceChecked[i] {
-			r := <-nonceResults
-			nonceChecked[r.index] = true
-			if !r.valid {
-				invalid := chain[r.index]
-				return r.index, &BlockNonceErr{Hash: invalid.Hash(), Number: invalid.Number(), Nonce: invalid.Nonce()}
-			}
-		}
-
+		// If the header is a banned one, straight out abort
 		if BadHashes[block.Hash()] {
 			err := BadHashError(block.Hash())
 			self.reportBlock(block, nil, err)
 			return i, err
 		}
-		// Stage 1 validation of the block using the chain's validator
-		// interface.
-		err := self.Validator().ValidateBlock(block)
+		// Wait for the block's verification to complete
+		bstart := time.Now()
+
+		err := <-results
+		if err == nil {
+			err = self.Validator().ValidateBody(block)
+		}
 		if err != nil {
 			if IsKnownBlockErr(err) {
 				stats.ignored++
@@ -952,7 +943,6 @@ func (self *BlockChain) InsertChain(chain types.Blocks) (int, error) {
 				if block.Time().Cmp(max) == 1 {
 					return i, fmt.Errorf("%v: BlockFutureErr, %v > %v", BlockFutureErr, block.Time(), max)
 				}
-
 				self.futureBlocks.Add(block.Hash(), block)
 				stats.queued++
 				continue
diff --git a/core/blockchain_test.go b/core/blockchain_test.go
index 3da133a9e..b2fb226db 100644
--- a/core/blockchain_test.go
+++ b/core/blockchain_test.go
@@ -24,6 +24,7 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
@@ -31,18 +32,21 @@ import (
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 // newTestBlockChain creates a blockchain without validation.
-func newTestBlockChain() *BlockChain {
+func newTestBlockChain(fake bool) *BlockChain {
 	db, _ := ethdb.NewMemDatabase()
 	gspec := &Genesis{
 		Config:     params.TestChainConfig,
 		Difficulty: big.NewInt(1),
 	}
 	gspec.MustCommit(db)
-	blockchain, err := NewBlockChain(db, gspec.Config, pow.FakePow{}, new(event.TypeMux), vm.Config{})
+	engine := ethash.NewFullFaker()
+	if !fake {
+		engine = ethash.NewTester()
+	}
+	blockchain, err := NewBlockChain(db, gspec.Config, engine, new(event.TypeMux), vm.Config{})
 	if err != nil {
 		panic(err)
 	}
@@ -117,7 +121,10 @@ func printChain(bc *BlockChain) {
 func testBlockChainImport(chain types.Blocks, blockchain *BlockChain) error {
 	for _, block := range chain {
 		// Try and process the block
-		err := blockchain.Validator().ValidateBlock(block)
+		err := blockchain.engine.VerifyHeader(blockchain, block.Header(), true)
+		if err == nil {
+			err = blockchain.validator.ValidateBody(block)
+		}
 		if err != nil {
 			if IsKnownBlockErr(err) {
 				continue
@@ -133,7 +140,7 @@ func testBlockChainImport(chain types.Blocks, blockchain *BlockChain) error {
 			blockchain.reportBlock(block, receipts, err)
 			return err
 		}
-		err = blockchain.Validator().ValidateState(block, blockchain.GetBlockByHash(block.ParentHash()), statedb, receipts, usedGas)
+		err = blockchain.validator.ValidateState(block, blockchain.GetBlockByHash(block.ParentHash()), statedb, receipts, usedGas)
 		if err != nil {
 			blockchain.reportBlock(block, receipts, err)
 			return err
@@ -152,7 +159,7 @@ func testBlockChainImport(chain types.Blocks, blockchain *BlockChain) error {
 func testHeaderChainImport(chain []*types.Header, blockchain *BlockChain) error {
 	for _, header := range chain {
 		// Try and validate the header
-		if err := blockchain.Validator().ValidateHeader(header, blockchain.GetHeaderByHash(header.ParentHash), false); err != nil {
+		if err := blockchain.engine.VerifyHeader(blockchain, header, false); err != nil {
 			return err
 		}
 		// Manually insert the header into the database, but don't reorganise (allows subsequent testing)
@@ -174,7 +181,7 @@ func insertChain(done chan bool, blockchain *BlockChain, chain types.Blocks, t *
 }
 
 func TestLastBlock(t *testing.T) {
-	bchain := newTestBlockChain()
+	bchain := newTestBlockChain(false)
 	block := makeBlockChain(bchain.CurrentBlock(), 1, bchain.chainDb, 0)[0]
 	bchain.insert(block)
 	if block.Hash() != GetHeadBlockHash(bchain.chainDb) {
@@ -318,8 +325,7 @@ func testBrokenChain(t *testing.T, full bool) {
 
 type bproc struct{}
 
-func (bproc) ValidateBlock(*types.Block) error                        { return nil }
-func (bproc) ValidateHeader(*types.Header, *types.Header, bool) error { return nil }
+func (bproc) ValidateBody(*types.Block) error { return nil }
 func (bproc) ValidateState(block, parent *types.Block, state *state.StateDB, receipts types.Receipts, usedGas *big.Int) error {
 	return nil
 }
@@ -378,7 +384,7 @@ func testReorgShort(t *testing.T, full bool) {
 }
 
 func testReorg(t *testing.T, first, second []int, td int64, full bool) {
-	bc := newTestBlockChain()
+	bc := newTestBlockChain(true)
 
 	// Insert an easy and a difficult chain afterwards
 	if full {
@@ -422,7 +428,7 @@ func TestBadHeaderHashes(t *testing.T) { testBadHashes(t, false) }
 func TestBadBlockHashes(t *testing.T)  { testBadHashes(t, true) }
 
 func testBadHashes(t *testing.T, full bool) {
-	bc := newTestBlockChain()
+	bc := newTestBlockChain(true)
 
 	// Create a chain, ban a hash and try to import
 	var err error
@@ -446,7 +452,7 @@ func TestReorgBadHeaderHashes(t *testing.T) { testReorgBadHashes(t, false) }
 func TestReorgBadBlockHashes(t *testing.T)  { testReorgBadHashes(t, true) }
 
 func testReorgBadHashes(t *testing.T, full bool) {
-	bc := newTestBlockChain()
+	bc := newTestBlockChain(true)
 
 	// Create a chain, import and ban afterwards
 	headers := makeHeaderChainWithDiff(bc.genesisBlock, []int{1, 2, 3, 4}, 10)
@@ -473,7 +479,7 @@ func testReorgBadHashes(t *testing.T, full bool) {
 	}
 
 	// Create a new BlockChain and check that it rolled back the state.
-	ncm, err := NewBlockChain(bc.chainDb, bc.config, pow.FakePow{}, new(event.TypeMux), vm.Config{})
+	ncm, err := NewBlockChain(bc.chainDb, bc.config, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 	if err != nil {
 		t.Fatalf("failed to create new chain manager: %v", err)
 	}
@@ -504,46 +510,34 @@ func testInsertNonceError(t *testing.T, full bool) {
 		}
 		// Create and insert a chain with a failing nonce
 		var (
-			failAt   int
-			failRes  int
-			failNum  uint64
-			failHash common.Hash
+			failAt  int
+			failRes int
+			failNum uint64
 		)
 		if full {
 			blocks := makeBlockChain(blockchain.CurrentBlock(), i, db, 0)
 
 			failAt = rand.Int() % len(blocks)
 			failNum = blocks[failAt].NumberU64()
-			failHash = blocks[failAt].Hash()
-
-			blockchain.pow = failPow{failNum}
 
+			blockchain.engine = ethash.NewFakeFailer(failNum)
 			failRes, err = blockchain.InsertChain(blocks)
 		} else {
 			headers := makeHeaderChain(blockchain.CurrentHeader(), i, db, 0)
 
 			failAt = rand.Int() % len(headers)
 			failNum = headers[failAt].Number.Uint64()
-			failHash = headers[failAt].Hash()
-
-			blockchain.pow = failPow{failNum}
-			blockchain.validator = NewBlockValidator(params.TestChainConfig, blockchain, failPow{failNum})
 
+			blockchain.engine = ethash.NewFakeFailer(failNum)
+			blockchain.hc.engine = blockchain.engine
 			failRes, err = blockchain.InsertHeaderChain(headers, 1)
 		}
 		// Check that the returned error indicates the nonce failure.
 		if failRes != failAt {
 			t.Errorf("test %d: failure index mismatch: have %d, want %d", i, failRes, failAt)
 		}
-		if !IsBlockNonceErr(err) {
-			t.Fatalf("test %d: error mismatch: have %v, want nonce error %T", i, err, err)
-		}
-		nerr := err.(*BlockNonceErr)
-		if nerr.Number.Uint64() != failNum {
-			t.Errorf("test %d: number mismatch: have %v, want %v", i, nerr.Number, failNum)
-		}
-		if nerr.Hash != failHash {
-			t.Errorf("test %d: hash mismatch: have %x, want %x", i, nerr.Hash[:4], failHash[:4])
+		if err != ethash.ErrInvalidPoW {
+			t.Fatalf("test %d: error mismatch: have %v, want %v", i, err, ethash.ErrInvalidPoW)
 		}
 		// Check that all no blocks after the failing block have been inserted.
 		for j := 0; j < i-failAt; j++ {
@@ -569,9 +563,12 @@ func TestFastVsFullChains(t *testing.T) {
 		key, _   = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 		address  = crypto.PubkeyToAddress(key.PublicKey)
 		funds    = big.NewInt(1000000000)
-		gspec    = testGenesis(address, funds)
-		genesis  = gspec.MustCommit(gendb)
-		signer   = types.NewEIP155Signer(gspec.Config.ChainId)
+		gspec    = &Genesis{
+			Config: params.TestChainConfig,
+			Alloc:  GenesisAlloc{address: {Balance: funds}},
+		}
+		genesis = gspec.MustCommit(gendb)
+		signer  = types.NewEIP155Signer(gspec.Config.ChainId)
 	)
 	blocks, receipts := GenerateChain(gspec.Config, genesis, gendb, 1024, func(i int, block *BlockGen) {
 		block.SetCoinbase(common.Address{0x00})
@@ -594,7 +591,7 @@ func TestFastVsFullChains(t *testing.T) {
 	// Import the chain as an archive node for the comparison baseline
 	archiveDb, _ := ethdb.NewMemDatabase()
 	gspec.MustCommit(archiveDb)
-	archive, _ := NewBlockChain(archiveDb, gspec.Config, pow.FakePow{}, new(event.TypeMux), vm.Config{})
+	archive, _ := NewBlockChain(archiveDb, gspec.Config, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 
 	if n, err := archive.InsertChain(blocks); err != nil {
 		t.Fatalf("failed to process block %d: %v", n, err)
@@ -603,7 +600,7 @@ func TestFastVsFullChains(t *testing.T) {
 	// Fast import the chain as a non-archive node to test
 	fastDb, _ := ethdb.NewMemDatabase()
 	gspec.MustCommit(fastDb)
-	fast, _ := NewBlockChain(fastDb, gspec.Config, pow.FakePow{}, new(event.TypeMux), vm.Config{})
+	fast, _ := NewBlockChain(fastDb, gspec.Config, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 
 	headers := make([]*types.Header, len(blocks))
 	for i, block := range blocks {
@@ -680,8 +677,7 @@ func TestLightVsFastVsFullChainHeads(t *testing.T) {
 	archiveDb, _ := ethdb.NewMemDatabase()
 	gspec.MustCommit(archiveDb)
 
-	archive, _ := NewBlockChain(archiveDb, gspec.Config, pow.FakePow{}, new(event.TypeMux), vm.Config{})
-
+	archive, _ := NewBlockChain(archiveDb, gspec.Config, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 	if n, err := archive.InsertChain(blocks); err != nil {
 		t.Fatalf("failed to process block %d: %v", n, err)
 	}
@@ -692,7 +688,7 @@ func TestLightVsFastVsFullChainHeads(t *testing.T) {
 	// Import the chain as a non-archive node and ensure all pointers are updated
 	fastDb, _ := ethdb.NewMemDatabase()
 	gspec.MustCommit(fastDb)
-	fast, _ := NewBlockChain(fastDb, gspec.Config, pow.FakePow{}, new(event.TypeMux), vm.Config{})
+	fast, _ := NewBlockChain(fastDb, gspec.Config, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 
 	headers := make([]*types.Header, len(blocks))
 	for i, block := range blocks {
@@ -711,8 +707,8 @@ func TestLightVsFastVsFullChainHeads(t *testing.T) {
 	// Import the chain as a light node and ensure all pointers are updated
 	lightDb, _ := ethdb.NewMemDatabase()
 	gspec.MustCommit(lightDb)
-	light, _ := NewBlockChain(lightDb, gspec.Config, pow.FakePow{}, new(event.TypeMux), vm.Config{})
 
+	light, _ := NewBlockChain(lightDb, gspec.Config, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 	if n, err := light.InsertHeaderChain(headers, 1); err != nil {
 		t.Fatalf("failed to insert header %d: %v", n, err)
 	}
@@ -780,7 +776,7 @@ func TestChainTxReorgs(t *testing.T) {
 	})
 	// Import the chain. This runs all block validation rules.
 	evmux := &event.TypeMux{}
-	blockchain, _ := NewBlockChain(db, gspec.Config, pow.FakePow{}, evmux, vm.Config{})
+	blockchain, _ := NewBlockChain(db, gspec.Config, ethash.NewFaker(), evmux, vm.Config{})
 	if i, err := blockchain.InsertChain(chain); err != nil {
 		t.Fatalf("failed to insert original chain[%d]: %v", i, err)
 	}
@@ -851,7 +847,7 @@ func TestLogReorgs(t *testing.T) {
 	)
 
 	var evmux event.TypeMux
-	blockchain, _ := NewBlockChain(db, gspec.Config, pow.FakePow{}, &evmux, vm.Config{})
+	blockchain, _ := NewBlockChain(db, gspec.Config, ethash.NewFaker(), &evmux, vm.Config{})
 
 	subs := evmux.Subscribe(RemovedLogsEvent{})
 	chain, _ := GenerateChain(params.TestChainConfig, genesis, db, 2, func(i int, gen *BlockGen) {
@@ -883,13 +879,16 @@ func TestReorgSideEvent(t *testing.T) {
 		db, _   = ethdb.NewMemDatabase()
 		key1, _ = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 		addr1   = crypto.PubkeyToAddress(key1.PublicKey)
-		gspec   = testGenesis(addr1, big.NewInt(10000000000000))
+		gspec   = &Genesis{
+			Config: params.TestChainConfig,
+			Alloc:  GenesisAlloc{addr1: {Balance: big.NewInt(10000000000000)}},
+		}
 		genesis = gspec.MustCommit(db)
 		signer  = types.NewEIP155Signer(gspec.Config.ChainId)
 	)
 
 	evmux := &event.TypeMux{}
-	blockchain, _ := NewBlockChain(db, gspec.Config, pow.FakePow{}, evmux, vm.Config{})
+	blockchain, _ := NewBlockChain(db, gspec.Config, ethash.NewFaker(), evmux, vm.Config{})
 
 	chain, _ := GenerateChain(gspec.Config, genesis, db, 3, func(i int, gen *BlockGen) {})
 	if _, err := blockchain.InsertChain(chain); err != nil {
@@ -959,7 +958,7 @@ done:
 
 // Tests if the canonical block can be fetched from the database during chain insertion.
 func TestCanonicalBlockRetrieval(t *testing.T) {
-	bc := newTestBlockChain()
+	bc := newTestBlockChain(false)
 	chain, _ := GenerateChain(bc.config, bc.genesisBlock, bc.chainDb, 10, func(i int, gen *BlockGen) {})
 
 	for i := range chain {
@@ -1004,7 +1003,7 @@ func TestEIP155Transition(t *testing.T) {
 		mux     event.TypeMux
 	)
 
-	blockchain, _ := NewBlockChain(db, gspec.Config, pow.FakePow{}, &mux, vm.Config{})
+	blockchain, _ := NewBlockChain(db, gspec.Config, ethash.NewFaker(), &mux, vm.Config{})
 	blocks, _ := GenerateChain(gspec.Config, genesis, db, 4, func(i int, block *BlockGen) {
 		var (
 			tx      *types.Transaction
@@ -1110,7 +1109,7 @@ func TestEIP161AccountRemoval(t *testing.T) {
 		}
 		genesis       = gspec.MustCommit(db)
 		mux           event.TypeMux
-		blockchain, _ = NewBlockChain(db, gspec.Config, pow.FakePow{}, &mux, vm.Config{})
+		blockchain, _ = NewBlockChain(db, gspec.Config, ethash.NewFaker(), &mux, vm.Config{})
 	)
 	blocks, _ := GenerateChain(gspec.Config, genesis, db, 3, func(i int, block *BlockGen) {
 		var (
diff --git a/core/chain_makers.go b/core/chain_makers.go
index 5bf1ece25..c47c719f6 100644
--- a/core/chain_makers.go
+++ b/core/chain_makers.go
@@ -21,13 +21,14 @@ import (
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
+	"github.com/ethereum/go-ethereum/consensus/misc"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 // So we can deterministically seed different blockchains
@@ -141,7 +142,7 @@ func (b *BlockGen) OffsetTime(seconds int64) {
 	if b.header.Time.Cmp(b.parent.Header().Time) <= 0 {
 		panic("block time out of range")
 	}
-	b.header.Difficulty = CalcDifficulty(b.config, b.header.Time.Uint64(), b.parent.Time().Uint64(), b.parent.Number(), b.parent.Difficulty())
+	b.header.Difficulty = ethash.CalcDifficulty(b.config, b.header.Time.Uint64(), b.parent.Time().Uint64(), b.parent.Number(), b.parent.Difficulty())
 }
 
 // GenerateChain creates a chain of n blocks. The first block's
@@ -173,13 +174,13 @@ func GenerateChain(config *params.ChainConfig, parent *types.Block, db ethdb.Dat
 			}
 		}
 		if config.DAOForkSupport && config.DAOForkBlock != nil && config.DAOForkBlock.Cmp(h.Number) == 0 {
-			ApplyDAOHardFork(statedb)
+			misc.ApplyDAOHardFork(statedb)
 		}
 		// Execute any user modifications to the block and finalize it
 		if gen != nil {
 			gen(i, b)
 		}
-		AccumulateRewards(statedb, h, b.uncles)
+		ethash.AccumulateRewards(statedb, h, b.uncles)
 		root, err := statedb.Commit(config.IsEIP158(h.Number))
 		if err != nil {
 			panic(fmt.Sprintf("state write error: %v", err))
@@ -212,7 +213,7 @@ func makeHeader(config *params.ChainConfig, parent *types.Block, state *state.St
 		Root:       state.IntermediateRoot(config.IsEIP158(parent.Number())),
 		ParentHash: parent.Hash(),
 		Coinbase:   parent.Coinbase(),
-		Difficulty: CalcDifficulty(config, time.Uint64(), new(big.Int).Sub(time, big.NewInt(10)).Uint64(), parent.Number(), parent.Difficulty()),
+		Difficulty: ethash.CalcDifficulty(config, time.Uint64(), new(big.Int).Sub(time, big.NewInt(10)).Uint64(), parent.Number(), parent.Difficulty()),
 		GasLimit:   CalcGasLimit(parent),
 		GasUsed:    new(big.Int),
 		Number:     new(big.Int).Add(parent.Number(), common.Big1),
@@ -229,7 +230,7 @@ func newCanonical(n int, full bool) (ethdb.Database, *BlockChain, error) {
 	db, _ := ethdb.NewMemDatabase()
 	genesis := gspec.MustCommit(db)
 
-	blockchain, _ := NewBlockChain(db, params.AllProtocolChanges, pow.FakePow{}, new(event.TypeMux), vm.Config{})
+	blockchain, _ := NewBlockChain(db, params.AllProtocolChanges, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 	// Create and inject the requested chain
 	if n == 0 {
 		return db, blockchain, nil
diff --git a/core/chain_makers_test.go b/core/chain_makers_test.go
index a8f77cdf3..3a7c62396 100644
--- a/core/chain_makers_test.go
+++ b/core/chain_makers_test.go
@@ -20,13 +20,13 @@ import (
 	"fmt"
 	"math/big"
 
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 func ExampleGenerateChain() {
@@ -81,7 +81,7 @@ func ExampleGenerateChain() {
 
 	// Import the chain. This runs all block validation rules.
 	evmux := &event.TypeMux{}
-	blockchain, _ := NewBlockChain(db, gspec.Config, pow.FakePow{}, evmux, vm.Config{})
+	blockchain, _ := NewBlockChain(db, gspec.Config, ethash.NewFaker(), evmux, vm.Config{})
 	if i, err := blockchain.InsertChain(chain); err != nil {
 		fmt.Printf("insert error (block %d): %v\n", chain[i].NumberU64(), err)
 		return
diff --git a/core/chain_pow.go b/core/chain_pow.go
deleted file mode 100644
index e5ccd87e2..000000000
--- a/core/chain_pow.go
+++ /dev/null
@@ -1,87 +0,0 @@
-// Copyright 2015 The go-ethereum Authors
-// This file is part of the go-ethereum library.
-//
-// The go-ethereum library is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Lesser General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// The go-ethereum library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU Lesser General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
-
-package core
-
-import (
-	"runtime"
-
-	"github.com/ethereum/go-ethereum/core/types"
-	"github.com/ethereum/go-ethereum/pow"
-)
-
-// nonceCheckResult contains the result of a nonce verification.
-type nonceCheckResult struct {
-	index int  // Index of the item verified from an input array
-	valid bool // Result of the nonce verification
-}
-
-// verifyNoncesFromHeaders starts a concurrent header nonce verification,
-// returning a quit channel to abort the operations and a results channel
-// to retrieve the async verifications.
-func verifyNoncesFromHeaders(checker pow.PoW, headers []*types.Header) (chan<- struct{}, <-chan nonceCheckResult) {
-	items := make([]pow.Block, len(headers))
-	for i, header := range headers {
-		items[i] = types.NewBlockWithHeader(header)
-	}
-	return verifyNonces(checker, items)
-}
-
-// verifyNoncesFromBlocks starts a concurrent block nonce verification,
-// returning a quit channel to abort the operations and a results channel
-// to retrieve the async verifications.
-func verifyNoncesFromBlocks(checker pow.PoW, blocks []*types.Block) (chan<- struct{}, <-chan nonceCheckResult) {
-	items := make([]pow.Block, len(blocks))
-	for i, block := range blocks {
-		items[i] = block
-	}
-	return verifyNonces(checker, items)
-}
-
-// verifyNonces starts a concurrent nonce verification, returning a quit channel
-// to abort the operations and a results channel to retrieve the async checks.
-func verifyNonces(checker pow.PoW, items []pow.Block) (chan<- struct{}, <-chan nonceCheckResult) {
-	// Spawn as many workers as allowed threads
-	workers := runtime.GOMAXPROCS(0)
-	if len(items) < workers {
-		workers = len(items)
-	}
-	// Create a task channel and spawn the verifiers
-	tasks := make(chan int, workers)
-	results := make(chan nonceCheckResult, len(items)) // Buffered to make sure all workers stop
-	for i := 0; i < workers; i++ {
-		go func() {
-			for index := range tasks {
-				results <- nonceCheckResult{index: index, valid: checker.Verify(items[index]) == nil}
-			}
-		}()
-	}
-	// Feed item indices to the workers until done or aborted
-	abort := make(chan struct{})
-	go func() {
-		defer close(tasks)
-
-		for i := range items {
-			select {
-			case tasks <- i:
-				continue
-			case <-abort:
-				return
-			}
-		}
-	}()
-	return abort, results
-}
diff --git a/core/chain_pow_test.go b/core/chain_pow_test.go
deleted file mode 100644
index 311ca128e..000000000
--- a/core/chain_pow_test.go
+++ /dev/null
@@ -1,238 +0,0 @@
-// Copyright 2015 The go-ethereum Authors
-// This file is part of the go-ethereum library.
-//
-// The go-ethereum library is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Lesser General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// The go-ethereum library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU Lesser General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
-
-package core
-
-import (
-	"errors"
-	"math/big"
-	"runtime"
-	"testing"
-	"time"
-
-	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/core/types"
-	"github.com/ethereum/go-ethereum/ethdb"
-	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
-)
-
-// failPow is a non-validating proof of work implementation, that returns true
-// from Verify for all but one block.
-type failPow struct {
-	failing uint64
-}
-
-func (pow failPow) Search(pow.Block, <-chan struct{}) (uint64, []byte) {
-	return 0, nil
-}
-func (pow failPow) Verify(block pow.Block) error {
-	if block.NumberU64() == pow.failing {
-		return errors.New("failed")
-	}
-	return nil
-}
-func (pow failPow) Hashrate() float64 { return 0 }
-
-// delayedPow is a non-validating proof of work implementation, that returns true
-// from Verify for all blocks, but delays them the configured amount of time.
-type delayedPow struct {
-	delay time.Duration
-}
-
-func (pow delayedPow) Search(pow.Block, <-chan struct{}) (uint64, []byte) {
-	return 0, nil
-}
-func (pow delayedPow) Verify(block pow.Block) error { time.Sleep(pow.delay); return nil }
-func (pow delayedPow) Hashrate() float64            { return 0 }
-
-// Tests that simple POW verification works, for both good and bad blocks.
-func TestPowVerification(t *testing.T) {
-	// Create a simple chain to verify
-	var (
-		testdb, _ = ethdb.NewMemDatabase()
-		genesis   = GenesisBlockForTesting(testdb, common.Address{}, new(big.Int))
-		blocks, _ = GenerateChain(params.TestChainConfig, genesis, testdb, 8, nil)
-	)
-	headers := make([]*types.Header, len(blocks))
-	for i, block := range blocks {
-		headers[i] = block.Header()
-	}
-	// Run the POW checker for blocks one-by-one, checking for both valid and invalid nonces
-	for i := 0; i < len(blocks); i++ {
-		for j, full := range []bool{true, false} {
-			for k, valid := range []bool{true, false} {
-				var results <-chan nonceCheckResult
-
-				switch {
-				case full && valid:
-					_, results = verifyNoncesFromBlocks(pow.FakePow{}, []*types.Block{blocks[i]})
-				case full && !valid:
-					_, results = verifyNoncesFromBlocks(failPow{blocks[i].NumberU64()}, []*types.Block{blocks[i]})
-				case !full && valid:
-					_, results = verifyNoncesFromHeaders(pow.FakePow{}, []*types.Header{headers[i]})
-				case !full && !valid:
-					_, results = verifyNoncesFromHeaders(failPow{headers[i].Number.Uint64()}, []*types.Header{headers[i]})
-				}
-				// Wait for the verification result
-				select {
-				case result := <-results:
-					if result.index != 0 {
-						t.Errorf("test %d.%d.%d: invalid index: have %d, want 0", i, j, k, result.index)
-					}
-					if result.valid != valid {
-						t.Errorf("test %d.%d.%d: validity mismatch: have %v, want %v", i, j, k, result.valid, valid)
-					}
-				case <-time.After(time.Second):
-					t.Fatalf("test %d.%d.%d: verification timeout", i, j, k)
-				}
-				// Make sure no more data is returned
-				select {
-				case result := <-results:
-					t.Fatalf("test %d.%d.%d: unexpected result returned: %v", i, j, k, result)
-				case <-time.After(25 * time.Millisecond):
-				}
-			}
-		}
-	}
-}
-
-// Tests that concurrent POW verification works, for both good and bad blocks.
-func TestPowConcurrentVerification2(t *testing.T)  { testPowConcurrentVerification(t, 2) }
-func TestPowConcurrentVerification8(t *testing.T)  { testPowConcurrentVerification(t, 8) }
-func TestPowConcurrentVerification32(t *testing.T) { testPowConcurrentVerification(t, 32) }
-
-func testPowConcurrentVerification(t *testing.T, threads int) {
-	// Create a simple chain to verify
-	var (
-		testdb, _ = ethdb.NewMemDatabase()
-		genesis   = GenesisBlockForTesting(testdb, common.Address{}, new(big.Int))
-		blocks, _ = GenerateChain(params.TestChainConfig, genesis, testdb, 8, nil)
-	)
-	headers := make([]*types.Header, len(blocks))
-	for i, block := range blocks {
-		headers[i] = block.Header()
-	}
-	// Set the number of threads to verify on
-	old := runtime.GOMAXPROCS(threads)
-	defer runtime.GOMAXPROCS(old)
-
-	// Run the POW checker for the entire block chain at once both for a valid and
-	// also an invalid chain (enough if one is invalid, last but one (arbitrary)).
-	for i, full := range []bool{true, false} {
-		for j, valid := range []bool{true, false} {
-			var results <-chan nonceCheckResult
-
-			switch {
-			case full && valid:
-				_, results = verifyNoncesFromBlocks(pow.FakePow{}, blocks)
-			case full && !valid:
-				_, results = verifyNoncesFromBlocks(failPow{uint64(len(blocks) - 1)}, blocks)
-			case !full && valid:
-				_, results = verifyNoncesFromHeaders(pow.FakePow{}, headers)
-			case !full && !valid:
-				_, results = verifyNoncesFromHeaders(failPow{uint64(len(headers) - 1)}, headers)
-			}
-			// Wait for all the verification results
-			checks := make(map[int]bool)
-			for k := 0; k < len(blocks); k++ {
-				select {
-				case result := <-results:
-					if _, ok := checks[result.index]; ok {
-						t.Fatalf("test %d.%d.%d: duplicate results for %d", i, j, k, result.index)
-					}
-					if result.index < 0 || result.index >= len(blocks) {
-						t.Fatalf("test %d.%d.%d: result %d out of bounds [%d, %d]", i, j, k, result.index, 0, len(blocks)-1)
-					}
-					checks[result.index] = result.valid
-
-				case <-time.After(time.Second):
-					t.Fatalf("test %d.%d.%d: verification timeout", i, j, k)
-				}
-			}
-			// Check nonce check validity
-			for k := 0; k < len(blocks); k++ {
-				want := valid || (k != len(blocks)-2) // We chose the last but one nonce in the chain to fail
-				if checks[k] != want {
-					t.Errorf("test %d.%d.%d: validity mismatch: have %v, want %v", i, j, k, checks[k], want)
-				}
-			}
-			// Make sure no more data is returned
-			select {
-			case result := <-results:
-				t.Fatalf("test %d.%d: unexpected result returned: %v", i, j, result)
-			case <-time.After(25 * time.Millisecond):
-			}
-		}
-	}
-}
-
-// Tests that aborting a POW validation indeed prevents further checks from being
-// run, as well as checks that no left-over goroutines are leaked.
-func TestPowConcurrentAbortion2(t *testing.T)  { testPowConcurrentAbortion(t, 2) }
-func TestPowConcurrentAbortion8(t *testing.T)  { testPowConcurrentAbortion(t, 8) }
-func TestPowConcurrentAbortion32(t *testing.T) { testPowConcurrentAbortion(t, 32) }
-
-func testPowConcurrentAbortion(t *testing.T, threads int) {
-	// Create a simple chain to verify
-	var (
-		testdb, _ = ethdb.NewMemDatabase()
-		genesis   = GenesisBlockForTesting(testdb, common.Address{}, new(big.Int))
-		blocks, _ = GenerateChain(params.TestChainConfig, genesis, testdb, 1024, nil)
-	)
-	headers := make([]*types.Header, len(blocks))
-	for i, block := range blocks {
-		headers[i] = block.Header()
-	}
-	// Set the number of threads to verify on
-	old := runtime.GOMAXPROCS(threads)
-	defer runtime.GOMAXPROCS(old)
-
-	// Run the POW checker for the entire block chain at once
-	for i, full := range []bool{true, false} {
-		var abort chan<- struct{}
-		var results <-chan nonceCheckResult
-
-		// Start the verifications and immediately abort
-		if full {
-			abort, results = verifyNoncesFromBlocks(delayedPow{time.Millisecond}, blocks)
-		} else {
-			abort, results = verifyNoncesFromHeaders(delayedPow{time.Millisecond}, headers)
-		}
-		close(abort)
-
-		// Deplete the results channel
-		verified := make(map[int]struct{})
-		for depleted := false; !depleted; {
-			select {
-			case result := <-results:
-				verified[result.index] = struct{}{}
-			case <-time.After(50 * time.Millisecond):
-				depleted = true
-			}
-		}
-		// Check that abortion was honored by not processing too many POWs
-		if len(verified) > 2*threads {
-			t.Errorf("test %d: verification count too large: have %d, want below %d", i, len(verified), 2*threads)
-		}
-		// Check that there are no gaps in the results
-		for j := 0; j < len(verified); j++ {
-			if _, ok := verified[j]; !ok {
-				t.Errorf("test %d.%d: gap found in verification results", i, j)
-			}
-		}
-	}
-}
diff --git a/core/dao_test.go b/core/dao_test.go
index c0d482630..cb6e54f8f 100644
--- a/core/dao_test.go
+++ b/core/dao_test.go
@@ -20,11 +20,11 @@ import (
 	"math/big"
 	"testing"
 
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 // Tests that DAO-fork enabled clients can properly filter out fork-commencing
@@ -42,12 +42,12 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 	proDb, _ := ethdb.NewMemDatabase()
 	gspec.MustCommit(proDb)
 	proConf := &params.ChainConfig{HomesteadBlock: big.NewInt(0), DAOForkBlock: forkBlock, DAOForkSupport: true}
-	proBc, _ := NewBlockChain(proDb, proConf, new(pow.FakePow), new(event.TypeMux), vm.Config{})
+	proBc, _ := NewBlockChain(proDb, proConf, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 
 	conDb, _ := ethdb.NewMemDatabase()
 	gspec.MustCommit(conDb)
 	conConf := &params.ChainConfig{HomesteadBlock: big.NewInt(0), DAOForkBlock: forkBlock, DAOForkSupport: false}
-	conBc, _ := NewBlockChain(conDb, conConf, new(pow.FakePow), new(event.TypeMux), vm.Config{})
+	conBc, _ := NewBlockChain(conDb, conConf, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 
 	if _, err := proBc.InsertChain(prefix); err != nil {
 		t.Fatalf("pro-fork: failed to import chain prefix: %v", err)
@@ -60,7 +60,7 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 		// Create a pro-fork block, and try to feed into the no-fork chain
 		db, _ = ethdb.NewMemDatabase()
 		gspec.MustCommit(db)
-		bc, _ := NewBlockChain(db, conConf, new(pow.FakePow), new(event.TypeMux), vm.Config{})
+		bc, _ := NewBlockChain(db, conConf, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 
 		blocks := conBc.GetBlocksFromHash(conBc.CurrentBlock().Hash(), int(conBc.CurrentBlock().NumberU64()+1))
 		for j := 0; j < len(blocks)/2; j++ {
@@ -81,7 +81,7 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 		// Create a no-fork block, and try to feed into the pro-fork chain
 		db, _ = ethdb.NewMemDatabase()
 		gspec.MustCommit(db)
-		bc, _ = NewBlockChain(db, proConf, new(pow.FakePow), new(event.TypeMux), vm.Config{})
+		bc, _ = NewBlockChain(db, proConf, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 
 		blocks = proBc.GetBlocksFromHash(proBc.CurrentBlock().Hash(), int(proBc.CurrentBlock().NumberU64()+1))
 		for j := 0; j < len(blocks)/2; j++ {
@@ -103,7 +103,7 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 	// Verify that contra-forkers accept pro-fork extra-datas after forking finishes
 	db, _ = ethdb.NewMemDatabase()
 	gspec.MustCommit(db)
-	bc, _ := NewBlockChain(db, conConf, new(pow.FakePow), new(event.TypeMux), vm.Config{})
+	bc, _ := NewBlockChain(db, conConf, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 
 	blocks := conBc.GetBlocksFromHash(conBc.CurrentBlock().Hash(), int(conBc.CurrentBlock().NumberU64()+1))
 	for j := 0; j < len(blocks)/2; j++ {
@@ -119,7 +119,7 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 	// Verify that pro-forkers accept contra-fork extra-datas after forking finishes
 	db, _ = ethdb.NewMemDatabase()
 	gspec.MustCommit(db)
-	bc, _ = NewBlockChain(db, proConf, new(pow.FakePow), new(event.TypeMux), vm.Config{})
+	bc, _ = NewBlockChain(db, proConf, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 
 	blocks = proBc.GetBlocksFromHash(proBc.CurrentBlock().Hash(), int(proBc.CurrentBlock().NumberU64()+1))
 	for j := 0; j < len(blocks)/2; j++ {
diff --git a/core/database_util_test.go b/core/database_util_test.go
index e6be06093..9f16b660a 100644
--- a/core/database_util_test.go
+++ b/core/database_util_test.go
@@ -18,14 +18,12 @@ package core
 
 import (
 	"bytes"
-	"encoding/json"
 	"io/ioutil"
 	"math/big"
 	"os"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/common/math"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/crypto/sha3"
@@ -34,58 +32,6 @@ import (
 	"github.com/ethereum/go-ethereum/rlp"
 )
 
-type diffTest struct {
-	ParentTimestamp    uint64
-	ParentDifficulty   *big.Int
-	CurrentTimestamp   uint64
-	CurrentBlocknumber *big.Int
-	CurrentDifficulty  *big.Int
-}
-
-func (d *diffTest) UnmarshalJSON(b []byte) (err error) {
-	var ext struct {
-		ParentTimestamp    string
-		ParentDifficulty   string
-		CurrentTimestamp   string
-		CurrentBlocknumber string
-		CurrentDifficulty  string
-	}
-	if err := json.Unmarshal(b, &ext); err != nil {
-		return err
-	}
-
-	d.ParentTimestamp = math.MustParseUint64(ext.ParentTimestamp)
-	d.ParentDifficulty = math.MustParseBig256(ext.ParentDifficulty)
-	d.CurrentTimestamp = math.MustParseUint64(ext.CurrentTimestamp)
-	d.CurrentBlocknumber = math.MustParseBig256(ext.CurrentBlocknumber)
-	d.CurrentDifficulty = math.MustParseBig256(ext.CurrentDifficulty)
-
-	return nil
-}
-
-func TestCalcDifficulty(t *testing.T) {
-	file, err := os.Open("../tests/files/BasicTests/difficulty.json")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer file.Close()
-
-	tests := make(map[string]diffTest)
-	err = json.NewDecoder(file).Decode(&tests)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	config := &params.ChainConfig{HomesteadBlock: big.NewInt(1150000)}
-	for name, test := range tests {
-		number := new(big.Int).Sub(test.CurrentBlocknumber, big.NewInt(1))
-		diff := CalcDifficulty(config, test.CurrentTimestamp, test.ParentTimestamp, number, test.ParentDifficulty)
-		if diff.Cmp(test.CurrentDifficulty) != 0 {
-			t.Error(name, "failed. Expected", test.CurrentDifficulty, "and calculated", diff)
-		}
-	}
-}
-
 // Tests block header storage and retrieval operations.
 func TestHeaderStorage(t *testing.T) {
 	db, _ := ethdb.NewMemDatabase()
@@ -562,7 +508,11 @@ func TestMipmapChain(t *testing.T) {
 	)
 	defer db.Close()
 
-	genesis := testGenesis(addr, big.NewInt(1000000)).MustCommit(db)
+	gspec := &Genesis{
+		Config: params.TestChainConfig,
+		Alloc:  GenesisAlloc{addr: {Balance: big.NewInt(1000000)}},
+	}
+	genesis := gspec.MustCommit(db)
 	chain, receipts := GenerateChain(params.TestChainConfig, genesis, db, 1010, func(i int, gen *BlockGen) {
 		var receipts types.Receipts
 		switch i {
diff --git a/core/genesis_test.go b/core/genesis_test.go
index b73dd776f..4312a80b8 100644
--- a/core/genesis_test.go
+++ b/core/genesis_test.go
@@ -23,11 +23,11 @@ import (
 
 	"github.com/davecgh/go-spew/spew"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 func TestDefaultGenesisBlock(t *testing.T) {
@@ -119,7 +119,7 @@ func TestSetupGenesis(t *testing.T) {
 				// Commit the 'old' genesis block with Homestead transition at #2.
 				// Advance to block #4, past the homestead transition block of customg.
 				genesis := oldcustomg.MustCommit(db)
-				bc, _ := NewBlockChain(db, oldcustomg.Config, pow.FakePow{}, new(event.TypeMux), vm.Config{})
+				bc, _ := NewBlockChain(db, oldcustomg.Config, ethash.NewFullFaker(), new(event.TypeMux), vm.Config{})
 				bc.SetValidator(bproc{})
 				bc.InsertChain(makeBlockChainWithDiff(genesis, []int{2, 3, 4, 5}, 0))
 				bc.CurrentBlock()
diff --git a/core/headerchain.go b/core/headerchain.go
index e7660cc60..e2d0ff5b1 100644
--- a/core/headerchain.go
+++ b/core/headerchain.go
@@ -18,21 +18,19 @@ package core
 
 import (
 	crand "crypto/rand"
+	"errors"
 	"fmt"
 	"math"
 	"math/big"
 	mrand "math/rand"
-	"runtime"
-	"sync"
-	"sync/atomic"
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 	"github.com/hashicorp/golang-lru"
 )
 
@@ -62,18 +60,15 @@ type HeaderChain struct {
 
 	procInterrupt func() bool
 
-	rand         *mrand.Rand
-	getValidator getHeaderValidatorFn
+	rand   *mrand.Rand
+	engine consensus.Engine
 }
 
-// getHeaderValidatorFn returns a HeaderValidator interface
-type getHeaderValidatorFn func() HeaderValidator
-
 // NewHeaderChain creates a new HeaderChain structure.
 //  getValidator should return the parent's validator
 //  procInterrupt points to the parent's interrupt semaphore
 //  wg points to the parent's shutdown wait group
-func NewHeaderChain(chainDb ethdb.Database, config *params.ChainConfig, getValidator getHeaderValidatorFn, procInterrupt func() bool) (*HeaderChain, error) {
+func NewHeaderChain(chainDb ethdb.Database, config *params.ChainConfig, engine consensus.Engine, procInterrupt func() bool) (*HeaderChain, error) {
 	headerCache, _ := lru.New(headerCacheLimit)
 	tdCache, _ := lru.New(tdCacheLimit)
 	numberCache, _ := lru.New(numberCacheLimit)
@@ -92,7 +87,7 @@ func NewHeaderChain(chainDb ethdb.Database, config *params.ChainConfig, getValid
 		numberCache:   numberCache,
 		procInterrupt: procInterrupt,
 		rand:          mrand.New(mrand.NewSource(seed.Int64())),
-		getValidator:  getValidator,
+		engine:        engine,
 	}
 
 	hc.genesisHeader = hc.GetHeaderByNumber(0)
@@ -228,78 +223,34 @@ func (hc *HeaderChain) ValidateHeaderChain(chain []*types.Header, checkFreq int)
 		}
 	}
 
-	// Generate the list of headers that should be POW verified
-	verify := make([]bool, len(chain))
-	for i := 0; i < len(verify)/checkFreq; i++ {
+	// Generate the list of seal verification requests, and start the parallel verifier
+	seals := make([]bool, len(chain))
+	for i := 0; i < len(seals)/checkFreq; i++ {
 		index := i*checkFreq + hc.rand.Intn(checkFreq)
-		if index >= len(verify) {
-			index = len(verify) - 1
+		if index >= len(seals) {
+			index = len(seals) - 1
 		}
-		verify[index] = true
-	}
-	verify[len(verify)-1] = true // Last should always be verified to avoid junk
-
-	// Create the header verification task queue and worker functions
-	tasks := make(chan int, len(chain))
-	for i := 0; i < len(chain); i++ {
-		tasks <- i
+		seals[index] = true
 	}
-	close(tasks)
+	seals[len(seals)-1] = true // Last should always be verified to avoid junk
 
-	errs, failed := make([]error, len(tasks)), int32(0)
-	process := func(worker int) {
-		for index := range tasks {
-			header, hash := chain[index], chain[index].Hash()
+	abort, results := hc.engine.VerifyHeaders(hc, chain, seals)
+	defer close(abort)
 
-			// Short circuit insertion if shutting down or processing failed
-			if hc.procInterrupt() {
-				return
-			}
-			if atomic.LoadInt32(&failed) > 0 {
-				return
-			}
-			// Short circuit if the header is bad or already known
-			if BadHashes[hash] {
-				errs[index] = BadHashError(hash)
-				atomic.AddInt32(&failed, 1)
-				return
-			}
-			if hc.HasHeader(hash) {
-				continue
-			}
-			// Verify that the header honors the chain parameters
-			checkPow := verify[index]
-
-			var err error
-			if index == 0 {
-				err = hc.getValidator().ValidateHeader(header, hc.GetHeader(header.ParentHash, header.Number.Uint64()-1), checkPow)
-			} else {
-				err = hc.getValidator().ValidateHeader(header, chain[index-1], checkPow)
-			}
-			if err != nil {
-				errs[index] = err
-				atomic.AddInt32(&failed, 1)
-				return
-			}
+	// Iterate over the headers and ensure they all check out
+	for i, header := range chain {
+		// If the chain is terminating, stop processing blocks
+		if hc.procInterrupt() {
+			log.Debug("Premature abort during headers verification")
+			return 0, errors.New("aborted")
 		}
-	}
-	// Start as many worker threads as goroutines allowed
-	pending := new(sync.WaitGroup)
-	for i := 0; i < runtime.GOMAXPROCS(0); i++ {
-		pending.Add(1)
-		go func(id int) {
-			defer pending.Done()
-			process(id)
-		}(i)
-	}
-	pending.Wait()
-
-	// If anything failed, report
-	if failed > 0 {
-		for i, err := range errs {
-			if err != nil {
-				return i, err
-			}
+		// If the header is a banned one, straight out abort
+		if BadHashes[header.Hash()] {
+			return i, BadHashError(header.Hash())
+		}
+		// Otherwise wait for headers checks and ensure they pass
+		if err := <-results; err != nil {
+			return i, err
 		}
 	}
 
@@ -313,13 +264,11 @@ func (hc *HeaderChain) InsertHeaderChain(chain []*types.Header, writeHeader WhCa
 	for i, header := range chain {
 		// Short circuit insertion if shutting down
 		if hc.procInterrupt() {
-			log.Debug("Premature abort during headers processing")
-			break
+			log.Debug("Premature abort during headers import")
+			return i, errors.New("aborted")
 		}
-		hash := header.Hash()
-
 		// If the header's already known, skip it, otherwise store
-		if hc.HasHeader(hash) {
+		if hc.GetHeader(header.Hash(), header.Number.Uint64()) != nil {
 			stats.ignored++
 			continue
 		}
@@ -490,35 +439,11 @@ func (hc *HeaderChain) SetGenesis(head *types.Header) {
 	hc.genesisHeader = head
 }
 
-// headerValidator is responsible for validating block headers
-//
-// headerValidator implements HeaderValidator.
-type headerValidator struct {
-	config *params.ChainConfig
-	hc     *HeaderChain // Canonical header chain
-	Pow    pow.PoW      // Proof of work used for validating
-}
-
-// NewBlockValidator returns a new block validator which is safe for re-use
-func NewHeaderValidator(config *params.ChainConfig, chain *HeaderChain, pow pow.PoW) HeaderValidator {
-	return &headerValidator{
-		config: config,
-		Pow:    pow,
-		hc:     chain,
-	}
-}
+// Config retrieves the header chain's chain configuration.
+func (hc *HeaderChain) Config() *params.ChainConfig { return hc.config }
 
-// ValidateHeader validates the given header and, depending on the pow arg,
-// checks the proof of work of the given header. Returns an error if the
-// validation failed.
-func (v *headerValidator) ValidateHeader(header, parent *types.Header, checkPow bool) error {
-	// Short circuit if the parent is missing.
-	if parent == nil {
-		return ParentError(header.ParentHash)
-	}
-	// Short circuit if the header's already known or its parent missing
-	if v.hc.HasHeader(header.Hash()) {
-		return nil
-	}
-	return ValidateHeader(v.config, v.Pow, header, parent, checkPow, false)
+// GetBlock implements consensus.ChainReader, and returns nil for every input as
+// a header chain does not have blocks available for retrieval.
+func (hc *HeaderChain) GetBlock(hash common.Hash, number uint64) *types.Block {
+	return nil
 }
diff --git a/core/state_processor.go b/core/state_processor.go
index 3edc042a3..aca2929eb 100644
--- a/core/state_processor.go
+++ b/core/state_processor.go
@@ -19,6 +19,8 @@ package core
 import (
 	"math/big"
 
+	"github.com/ethereum/go-ethereum/consensus"
+	"github.com/ethereum/go-ethereum/consensus/misc"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
@@ -26,25 +28,22 @@ import (
 	"github.com/ethereum/go-ethereum/params"
 )
 
-var (
-	big8  = big.NewInt(8)
-	big32 = big.NewInt(32)
-)
-
 // StateProcessor is a basic Processor, which takes care of transitioning
 // state from one point to another.
 //
 // StateProcessor implements Processor.
 type StateProcessor struct {
-	config *params.ChainConfig
-	bc     *BlockChain
+	config *params.ChainConfig // Chain configuration options
+	bc     *BlockChain         // Canonical block chain
+	engine consensus.Engine    // Consensus engine used for block rewards
 }
 
 // NewStateProcessor initialises a new StateProcessor.
-func NewStateProcessor(config *params.ChainConfig, bc *BlockChain) *StateProcessor {
+func NewStateProcessor(config *params.ChainConfig, bc *BlockChain, engine consensus.Engine) *StateProcessor {
 	return &StateProcessor{
 		config: config,
 		bc:     bc,
+		engine: engine,
 	}
 }
 
@@ -59,18 +58,16 @@ func (p *StateProcessor) Process(block *types.Block, statedb *state.StateDB, cfg
 	var (
 		receipts     types.Receipts
 		totalUsedGas = big.NewInt(0)
-		err          error
 		header       = block.Header()
 		allLogs      []*types.Log
 		gp           = new(GasPool).AddGas(block.GasLimit())
 	)
 	// Mutate the the block and state according to any hard-fork specs
 	if p.config.DAOForkSupport && p.config.DAOForkBlock != nil && p.config.DAOForkBlock.Cmp(block.Number()) == 0 {
-		ApplyDAOHardFork(statedb)
+		misc.ApplyDAOHardFork(statedb)
 	}
 	// Iterate over and process the individual transactions
 	for i, tx := range block.Transactions() {
-		//fmt.Println("tx:", i)
 		statedb.StartRecord(tx.Hash(), block.Hash(), i)
 		receipt, _, err := ApplyTransaction(p.config, p.bc, gp, statedb, header, tx, totalUsedGas, cfg)
 		if err != nil {
@@ -79,9 +76,10 @@ func (p *StateProcessor) Process(block *types.Block, statedb *state.StateDB, cfg
 		receipts = append(receipts, receipt)
 		allLogs = append(allLogs, receipt.Logs...)
 	}
-	AccumulateRewards(statedb, header, block.Uncles())
+	// Finalize the block, applying any consensus engine specific extras (e.g. block rewards)
+	p.engine.Finalize(p.bc, header, statedb, block.Transactions(), block.Uncles(), receipts)
 
-	return receipts, allLogs, totalUsedGas, err
+	return receipts, allLogs, totalUsedGas, nil
 }
 
 // ApplyTransaction attempts to apply a transaction to the given state database
@@ -122,23 +120,3 @@ func ApplyTransaction(config *params.ChainConfig, bc *BlockChain, gp *GasPool, s
 
 	return receipt, gas, err
 }
-
-// AccumulateRewards credits the coinbase of the given block with the
-// mining reward. The total reward consists of the static block reward
-// and rewards for included uncles. The coinbase of each uncle block is
-// also rewarded.
-func AccumulateRewards(statedb *state.StateDB, header *types.Header, uncles []*types.Header) {
-	reward := new(big.Int).Set(BlockReward)
-	r := new(big.Int)
-	for _, uncle := range uncles {
-		r.Add(uncle.Number, big8)
-		r.Sub(r, header.Number)
-		r.Mul(r, BlockReward)
-		r.Div(r, big8)
-		statedb.AddBalance(uncle.Coinbase, r)
-
-		r.Div(BlockReward, big32)
-		reward.Add(reward, r)
-	}
-	statedb.AddBalance(header.Coinbase, reward)
-}
diff --git a/core/types.go b/core/types.go
index 7fd658979..1cfbbab29 100644
--- a/core/types.go
+++ b/core/types.go
@@ -24,31 +24,17 @@ import (
 	"github.com/ethereum/go-ethereum/core/vm"
 )
 
-// Validator is an interface which defines the standard for block validation.
+// Validator is an interface which defines the standard for block validation. It
+// is only responsible for validating block contents, as the header validation is
+// done by the specific consensus engines.
 //
-// The validator is responsible for validating incoming block or, if desired,
-// validates headers for fast validation.
-//
-// ValidateBlock validates the given block and should return an error if it
-// failed to do so and should be used for "full" validation.
-//
-// ValidateHeader validates the given header and parent and returns an error
-// if it failed to do so.
-//
-// ValidateState validates the given statedb and optionally the receipts and
-// gas used. The implementer should decide what to do with the given input.
 type Validator interface {
-	HeaderValidator
-	ValidateBlock(block *types.Block) error
-	ValidateState(block, parent *types.Block, state *state.StateDB, receipts types.Receipts, usedGas *big.Int) error
-}
+	// ValidateBody validates the given block's content.
+	ValidateBody(block *types.Block) error
 
-// HeaderValidator is an interface for validating headers only
-//
-// ValidateHeader validates the given header and parent and returns an error
-// if it failed to do so.
-type HeaderValidator interface {
-	ValidateHeader(header, parent *types.Header, checkPow bool) error
+	// ValidateState validates the given statedb and optionally the receipts and
+	// gas used.
+	ValidateState(block, parent *types.Block, state *state.StateDB, receipts types.Receipts, usedGas *big.Int) error
 }
 
 // Processor is an interface for processing blocks using a given initial state.
diff --git a/core/types/block.go b/core/types/block.go
index b699ba686..278594d50 100644
--- a/core/types/block.go
+++ b/core/types/block.go
@@ -348,12 +348,11 @@ func CalcUncleHash(uncles []*Header) common.Hash {
 	return rlpHash(uncles)
 }
 
-// WithMiningResult returns a new block with the data from b
-// where nonce and mix digest are set to the provided values.
-func (b *Block) WithMiningResult(nonce BlockNonce, mixDigest common.Hash) *Block {
-	cpy := *b.header
-	cpy.Nonce = nonce
-	cpy.MixDigest = mixDigest
+// WithSeal returns a new block with the data from b but the header replaced with
+// the sealed one.
+func (b *Block) WithSeal(header *Header) *Block {
+	cpy := *header
+
 	return &Block{
 		header:       &cpy,
 		transactions: b.transactions,