diff --git a/core/block_processor.go b/core/block_processor.go
index 8974cd94b..a6632fca7 100644
--- a/core/block_processor.go
+++ b/core/block_processor.go
@@ -277,7 +277,7 @@ func (sm *BlockProcessor) ValidateBlock(block, parent *types.Block) error {
 
 	// Verify the nonce of the block. Return an error if it's not valid
 	if !sm.Pow.Verify(block) {
-		return ValidationError("Block's nonce is invalid (= %v)", ethutil.Bytes2Hex(block.Header().Nonce))
+		return ValidationError("Block's nonce is invalid (= %x)", block.Header().Nonce)
 	}
 
 	return nil
@@ -305,7 +305,7 @@ func (sm *BlockProcessor) AccumulateRewards(statedb *state.StateDB, block, paren
 		}
 
 		if !sm.Pow.Verify(types.NewBlockWithHeader(uncle)) {
-			return ValidationError("Uncle's nonce is invalid (= %v)", ethutil.Bytes2Hex(uncle.Nonce))
+			return ValidationError("Uncle's nonce is invalid (= %x)", uncle.Nonce)
 		}
 
 		r := new(big.Int)
diff --git a/core/chain_makers.go b/core/chain_makers.go
index 7afdfde0d..3248975e1 100644
--- a/core/chain_makers.go
+++ b/core/chain_makers.go
@@ -14,8 +14,8 @@ import (
 // So we can generate blocks easily
 type FakePow struct{}
 
-func (f FakePow) Search(block pow.Block, stop <-chan struct{}) ([]byte, []byte, []byte) {
-	return nil, nil, nil
+func (f FakePow) Search(block pow.Block, stop <-chan struct{}) (uint64, []byte, []byte) {
+	return 0, nil, nil
 }
 func (f FakePow) Verify(block pow.Block) bool { return true }
 func (f FakePow) GetHashrate() int64          { return 0 }
@@ -55,7 +55,7 @@ func NewCanonical(n int, db ethutil.Database) (*BlockProcessor, error) {
 
 // block time is fixed at 10 seconds
 func newBlockFromParent(addr []byte, parent *types.Block) *types.Block {
-	block := types.NewBlock(parent.Hash(), addr, parent.Root(), ethutil.BigPow(2, 32), nil, "")
+	block := types.NewBlock(parent.Hash(), addr, parent.Root(), ethutil.BigPow(2, 32), 0, "")
 	block.SetUncles(nil)
 	block.SetTransactions(nil)
 	block.SetReceipts(nil)
diff --git a/core/chain_manager.go b/core/chain_manager.go
index 13edeea95..6212fb842 100644
--- a/core/chain_manager.go
+++ b/core/chain_manager.go
@@ -197,7 +197,7 @@ func (bc *ChainManager) NewBlock(coinbase []byte) *types.Block {
 		coinbase,
 		root,
 		ethutil.BigPow(2, 32),
-		nil,
+		0,
 		"")
 	block.SetUncles(nil)
 	block.SetTransactions(nil)
diff --git a/core/genesis.go b/core/genesis.go
index decffc541..3e90aa91d 100644
--- a/core/genesis.go
+++ b/core/genesis.go
@@ -23,7 +23,7 @@ var EmptyShaList = crypto.Sha3(ethutil.Encode([]interface{}{}))
 var EmptyListRoot = crypto.Sha3(ethutil.Encode(""))
 
 func GenesisBlock(db ethutil.Database) *types.Block {
-	genesis := types.NewBlock(ZeroHash256, ZeroHash160, nil, big.NewInt(131072), crypto.Sha3(big.NewInt(42).Bytes()), "")
+	genesis := types.NewBlock(ZeroHash256, ZeroHash160, nil, big.NewInt(131072), 42, "")
 	genesis.Header().Number = ethutil.Big0
 	genesis.Header().GasLimit = big.NewInt(1000000)
 	genesis.Header().GasUsed = ethutil.Big0
diff --git a/core/types/block.go b/core/types/block.go
index 673c72003..358d0bc2d 100644
--- a/core/types/block.go
+++ b/core/types/block.go
@@ -39,8 +39,8 @@ type Header struct {
 	Time uint64
 	// Extra data
 	Extra string
-	// Block Nonce for verification
-	Nonce ethutil.Bytes
+	// Nonce
+	Nonce uint64
 	// Mix digest for quick checking to prevent DOS
 	MixDigest ethutil.Bytes
 	// SeedHash used for light client verification
@@ -94,7 +94,7 @@ type Block struct {
 	Reward   *big.Int
 }
 
-func NewBlock(parentHash []byte, coinbase []byte, root []byte, difficulty *big.Int, nonce []byte, extra string) *Block {
+func NewBlock(parentHash []byte, coinbase []byte, root []byte, difficulty *big.Int, nonce uint64, extra string) *Block {
 	header := &Header{
 		Root:       root,
 		ParentHash: parentHash,
@@ -195,7 +195,7 @@ func (self *Block) Number() *big.Int          { return self.header.Number }
 func (self *Block) NumberU64() uint64         { return self.header.Number.Uint64() }
 func (self *Block) MixDigest() []byte         { return self.header.MixDigest }
 func (self *Block) SeedHash() []byte          { return self.header.SeedHash }
-func (self *Block) Nonce() []byte             { return self.header.Nonce }
+func (self *Block) Nonce() uint64             { return self.header.Nonce }
 func (self *Block) Bloom() []byte             { return self.header.Bloom }
 func (self *Block) Coinbase() []byte          { return self.header.Coinbase }
 func (self *Block) Time() int64               { return int64(self.header.Time) }
@@ -267,7 +267,7 @@ func (self *Header) String() string {
 	GasUsed:	    %v
 	Time:		    %v
 	Extra:		    %v
-	Nonce:		    %x
+	Nonce:		    %d
 	MixDigest:          %x
 	SeedHash:           %x
 
diff --git a/miner/agent.go b/miner/agent.go
index 6c21d8015..6865d5a08 100644
--- a/miner/agent.go
+++ b/miner/agent.go
@@ -75,7 +75,7 @@ done:
 func (self *CpuMiner) mine(block *types.Block) {
 	minerlogger.Infof("(re)started agent[%d]. mining...\n", self.index)
 	nonce, mixDigest, seedHash := self.pow.Search(block, self.quitCurrentOp)
-	if nonce != nil {
+	if nonce != 0 {
 		self.returnCh <- Work{block.Number().Uint64(), nonce, mixDigest, seedHash}
 	}
 }
diff --git a/miner/worker.go b/miner/worker.go
index 1388b22b0..8904c9973 100644
--- a/miner/worker.go
+++ b/miner/worker.go
@@ -47,7 +47,7 @@ func env(block *types.Block, eth core.Backend) *environment {
 
 type Work struct {
 	Number    uint64
-	Nonce     []byte
+	Nonce     uint64
 	MixDigest []byte
 	SeedHash  []byte
 }
@@ -150,7 +150,7 @@ func (self *worker) wait() {
 		for work := range self.recv {
 			// Someone Successfully Mined!
 			block := self.current.block
-			if block.Number().Uint64() == work.Number && block.Nonce() == nil {
+			if block.Number().Uint64() == work.Number && block.Nonce() == 0 {
 				self.current.block.Header().Nonce = work.Nonce
 				self.current.block.Header().MixDigest = work.MixDigest
 				self.current.block.Header().SeedHash = work.SeedHash
@@ -242,7 +242,7 @@ func (self *worker) commitUncle(uncle *types.Header) error {
 	}
 
 	if !self.pow.Verify(types.NewBlockWithHeader(uncle)) {
-		return core.ValidationError("Uncle's nonce is invalid (= %v)", ethutil.Bytes2Hex(uncle.Nonce))
+		return core.ValidationError("Uncle's nonce is invalid (= %x)", uncle.Nonce)
 	}
 
 	uncleAccount := self.current.state.GetAccount(uncle.Coinbase)
diff --git a/pow/block.go b/pow/block.go
index eb07bc86e..3bc63978b 100644
--- a/pow/block.go
+++ b/pow/block.go
@@ -1,14 +1,15 @@
 package pow
 
 import (
-	"github.com/ethereum/go-ethereum/core/types"
 	"math/big"
+
+	"github.com/ethereum/go-ethereum/core/types"
 )
 
 type Block interface {
 	Difficulty() *big.Int
 	HashNoNonce() []byte
-	Nonce() []byte
+	Nonce() uint64
 	MixDigest() []byte
 	SeedHash() []byte
 	NumberU64() uint64
diff --git a/pow/ezp/pow.go b/pow/ezp/pow.go
index 49854c3d0..3ca502d06 100644
--- a/pow/ezp/pow.go
+++ b/pow/ezp/pow.go
@@ -1,11 +1,11 @@
 package ezp
 
 import (
+	"encoding/binary"
 	"math/big"
 	"math/rand"
 	"time"
 
-	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/crypto/sha3"
 	"github.com/ethereum/go-ethereum/ethutil"
 	"github.com/ethereum/go-ethereum/logger"
@@ -32,7 +32,7 @@ func (pow *EasyPow) Turbo(on bool) {
 	pow.turbo = on
 }
 
-func (pow *EasyPow) Search(block pow.Block, stop <-chan struct{}) ([]byte, []byte, []byte) {
+func (pow *EasyPow) Search(block pow.Block, stop <-chan struct{}) (uint64, []byte, []byte) {
 	r := rand.New(rand.NewSource(time.Now().UnixNano()))
 	hash := block.HashNoNonce()
 	diff := block.Difficulty()
@@ -57,7 +57,7 @@ empty:
 	for {
 		select {
 		case <-stop:
-			return nil, nil, nil
+			return 0, nil, nil
 		default:
 			i++
 
@@ -65,7 +65,7 @@ empty:
 			hashes := ((float64(1e9) / float64(elapsed)) * float64(i-starti)) / 1000
 			pow.HashRate = int64(hashes)
 
-			sha := crypto.Sha3(big.NewInt(r.Int63()).Bytes())
+			sha := uint64(r.Int63())
 			if verify(hash, diff, sha) {
 				return sha, nil, nil
 			}
@@ -75,16 +75,20 @@ empty:
 			time.Sleep(20 * time.Microsecond)
 		}
 	}
+
+	return 0, nil, nil
 }
 
 func (pow *EasyPow) Verify(block pow.Block) bool {
 	return Verify(block)
 }
 
-func verify(hash []byte, diff *big.Int, nonce []byte) bool {
+func verify(hash []byte, diff *big.Int, nonce uint64) bool {
 	sha := sha3.NewKeccak256()
 
-	d := append(hash, nonce...)
+	n := make([]byte, 8)
+	binary.PutUvarint(n, nonce)
+	d := append(hash, n...)
 	sha.Write(d)
 
 	verification := new(big.Int).Div(ethutil.BigPow(2, 256), diff)
diff --git a/pow/pow.go b/pow/pow.go
index 11aecbd6b..3908e5f76 100644
--- a/pow/pow.go
+++ b/pow/pow.go
@@ -1,7 +1,7 @@
 package pow
 
 type PoW interface {
-	Search(block Block, stop <-chan struct{}) ([]byte, []byte, []byte)
+	Search(block Block, stop <-chan struct{}) (uint64, []byte, []byte)
 	Verify(block Block) bool
 	GetHashrate() int64
 	Turbo(bool)