diff --git a/cmd/geth/main.go b/cmd/geth/main.go
index aacb588feb..3c2f37a233 100644
--- a/cmd/geth/main.go
+++ b/cmd/geth/main.go
@@ -536,7 +536,7 @@ func blockRecovery(ctx *cli.Context) {
 		glog.Fatalln("block not found. Recovery failed")
 	}
 
-	err = core.WriteHead(blockDb, block)
+	err = core.WriteHeadBlockMeta(blockDb, block)
 	if err != nil {
 		glog.Fatalln("block write err", err)
 	}
diff --git a/core/bench_test.go b/core/bench_test.go
index baae8a7a5e..cd36ee76a7 100644
--- a/core/bench_test.go
+++ b/core/bench_test.go
@@ -133,12 +133,12 @@ func genTxRing(naccounts int) func(int, *BlockGen) {
 // genUncles generates blocks with two uncle headers.
 func genUncles(i int, gen *BlockGen) {
 	if i >= 6 {
-		b2 := gen.PrevBlock(i - 6).Header()
+		b2 := gen.PrevBlock(i - 6).Header().Raw()
 		b2.Extra = []byte("foo")
-		gen.AddUncle(b2)
-		b3 := gen.PrevBlock(i - 6).Header()
+		gen.AddUncle(types.NewHeader(b2))
+		b3 := gen.PrevBlock(i - 6).Header().Raw()
 		b3.Extra = []byte("bar")
-		gen.AddUncle(b3)
+		gen.AddUncle(types.NewHeader(b3))
 	}
 }
 
diff --git a/core/block_cache_test.go b/core/block_cache_test.go
index ef826d5bda..5a08572785 100644
--- a/core/block_cache_test.go
+++ b/core/block_cache_test.go
@@ -27,8 +27,11 @@ import (
 func newChain(size int) (chain []*types.Block) {
 	var parentHash common.Hash
 	for i := 0; i < size; i++ {
-		head := &types.Header{ParentHash: parentHash, Number: big.NewInt(int64(i))}
-		block := types.NewBlock(head, nil, nil, nil)
+		header := &types.RawHeader{
+			ParentHash: parentHash,
+			Number:     big.NewInt(int64(i)),
+		}
+		block := types.NewBlock(header, nil, nil, nil)
 		chain = append(chain, block)
 		parentHash = block.Hash()
 	}
diff --git a/core/block_processor.go b/core/block_processor.go
index 1238fda7b9..9819126a8b 100644
--- a/core/block_processor.go
+++ b/core/block_processor.go
@@ -230,7 +230,7 @@ func (sm *BlockProcessor) processWithParent(block, parent *types.Block) (logs st
 	// Validate the received block's bloom with the one derived from the generated receipts.
 	// For valid blocks this should always validate to true.
 	rbloom := types.CreateBloom(receipts)
-	if rbloom != header.Bloom {
+	if rbloom != header.Bloom() {
 		err = fmt.Errorf("unable to replicate block's bloom=%x", rbloom)
 		return
 	}
@@ -238,21 +238,21 @@ func (sm *BlockProcessor) processWithParent(block, parent *types.Block) (logs st
 	// 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(txs)
-	if txSha != header.TxHash {
+	if txSha != header.TxHash() {
 		err = fmt.Errorf("invalid transaction root hash. received=%x calculated=%x", header.TxHash, txSha)
 		return
 	}
 
 	// Tre receipt Trie's root (R = (Tr [[H1, R1], ... [Hn, R1]]))
 	receiptSha := types.DeriveSha(receipts)
-	if receiptSha != header.ReceiptHash {
+	if receiptSha != header.ReceiptHash() {
 		err = fmt.Errorf("invalid receipt root hash. received=%x calculated=%x", header.ReceiptHash, receiptSha)
 		return
 	}
 
 	// Verify UncleHash before running other uncle validations
 	unclesSha := types.CalcUncleHash(uncles)
-	if unclesSha != header.UncleHash {
+	if unclesSha != header.UncleHash() {
 		err = fmt.Errorf("invalid uncles root hash. received=%x calculated=%x", header.UncleHash, unclesSha)
 		return
 	}
@@ -267,7 +267,7 @@ func (sm *BlockProcessor) processWithParent(block, parent *types.Block) (logs st
 	// Commit state objects/accounts to a temporary trie (does not save)
 	// used to calculate the state root.
 	state.SyncObjects()
-	if header.Root != state.Root() {
+	if header.Root() != state.Root() {
 		err = fmt.Errorf("invalid merkle root. received=%x got=%x", header.Root, state.Root())
 		return
 	}
@@ -291,16 +291,16 @@ func AccumulateRewards(statedb *state.StateDB, header *types.Header, uncles []*t
 	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.Add(uncle.Number(), big8)
+		r.Sub(r, header.Number())
 		r.Mul(r, BlockReward)
 		r.Div(r, big8)
-		statedb.AddBalance(uncle.Coinbase, r)
+		statedb.AddBalance(uncle.Coinbase(), r)
 
 		r.Div(BlockReward, big32)
 		reward.Add(reward, r)
 	}
-	statedb.AddBalance(header.Coinbase, reward)
+	statedb.AddBalance(header.Coinbase(), reward)
 }
 
 func (sm *BlockProcessor) VerifyUncles(statedb *state.StateDB, block, parent *types.Block) error {
@@ -333,11 +333,11 @@ func (sm *BlockProcessor) VerifyUncles(statedb *state.StateDB, block, parent *ty
 			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 uncleParent := uncle.ParentHash(); ancestors[uncleParent] == nil || uncleParent == parent.Hash() {
+			return UncleError("uncle[%d](%x)'s parent is not ancestor (%x)", i, hash[:4], uncleParent[:4])
 		}
 
-		if err := ValidateHeader(sm.Pow, uncle, ancestors[uncle.ParentHash], true, true); err != nil {
+		if err := ValidateHeader(sm.Pow, uncle, ancestors[uncle.ParentHash()], true, true); err != nil {
 			return ValidationError(fmt.Sprintf("uncle[%d](%x) header invalid: %v", i, hash[:4], err))
 		}
 	}
@@ -368,49 +368,49 @@ func (sm *BlockProcessor) GetLogs(block *types.Block) (logs state.Logs, err erro
 
 // See YP section 4.3.4. "Block Header Validity"
 // Validates a block. Returns an error if the block is invalid.
-func ValidateHeader(pow pow.PoW, block *types.Header, parent *types.Block, checkPow, uncle bool) error {
-	if big.NewInt(int64(len(block.Extra))).Cmp(params.MaximumExtraDataSize) == 1 {
-		return fmt.Errorf("Block extra data too long (%d)", len(block.Extra))
+func ValidateHeader(pow pow.PoW, header *types.Header, parent *types.Block, checkPow, uncle bool) error {
+	if big.NewInt(int64(len(header.Extra()))).Cmp(params.MaximumExtraDataSize) == 1 {
+		return fmt.Errorf("Header extra data too long (%d)", len(header.Extra()))
 	}
 
 	if uncle {
-		if block.Time.Cmp(common.MaxBig) == 1 {
+		if header.Time().Cmp(common.MaxBig) == 1 {
 			return BlockTSTooBigErr
 		}
 	} else {
-		if block.Time.Cmp(big.NewInt(time.Now().Unix())) == 1 {
+		if header.Time().Cmp(big.NewInt(time.Now().Unix())) == 1 {
 			return BlockFutureErr
 		}
 	}
-	if block.Time.Cmp(parent.Time()) != 1 {
+	if header.Time().Cmp(parent.Time()) != 1 {
 		return BlockEqualTSErr
 	}
 
-	expd := CalcDifficulty(block.Time.Uint64(), parent.Time().Uint64(), parent.Number(), parent.Difficulty())
-	if expd.Cmp(block.Difficulty) != 0 {
-		return fmt.Errorf("Difficulty check failed for block %v, %v", block.Difficulty, expd)
+	expd := CalcDifficulty(header.Time().Uint64(), parent.Time().Uint64(), parent.Number(), parent.Difficulty())
+	if expd.Cmp(header.Difficulty()) != 0 {
+		return fmt.Errorf("Difficulty check failed for header %v, %v", header.Difficulty(), expd)
 	}
 
 	var a, b *big.Int
 	a = parent.GasLimit()
-	a = a.Sub(a, block.GasLimit)
+	a = a.Sub(a, header.GasLimit())
 	a.Abs(a)
 	b = parent.GasLimit()
 	b = b.Div(b, params.GasLimitBoundDivisor)
-	if !(a.Cmp(b) < 0) || (block.GasLimit.Cmp(params.MinGasLimit) == -1) {
-		return fmt.Errorf("GasLimit check failed for block %v (%v > %v)", block.GasLimit, a, b)
+	if !(a.Cmp(b) < 0) || (header.GasLimit().Cmp(params.MinGasLimit) == -1) {
+		return fmt.Errorf("GasLimit check failed for header %v (%v > %v)", header.GasLimit(), a, b)
 	}
 
 	num := parent.Number()
-	num.Sub(block.Number, num)
+	num.Sub(header.Number(), num)
 	if num.Cmp(big.NewInt(1)) != 0 {
 		return BlockNumberErr
 	}
 
 	if checkPow {
-		// Verify the nonce of the block. Return an error if it's not valid
-		if !pow.Verify(types.NewBlockWithHeader(block)) {
-			return ValidationError("Block's nonce is invalid (= %x)", block.Nonce)
+		// Verify the nonce of the header. Return an error if it's not valid
+		if !pow.Verify(types.NewBlockWithHeader(header)) {
+			return ValidationError("Block's nonce is invalid (= %x)", header.Nonce())
 		}
 	}
 
diff --git a/core/block_processor_test.go b/core/block_processor_test.go
index e0b2d3313f..580129a247 100644
--- a/core/block_processor_test.go
+++ b/core/block_processor_test.go
@@ -48,13 +48,13 @@ func TestNumber(t *testing.T) {
 	statedb := state.New(chain.Genesis().Root(), chain.chainDb)
 	header := makeHeader(chain.Genesis(), statedb)
 	header.Number = big.NewInt(3)
-	err := ValidateHeader(pow, header, chain.Genesis(), false, false)
+	err := ValidateHeader(pow, types.NewHeader(header), chain.Genesis(), false, false)
 	if err != BlockNumberErr {
 		t.Errorf("expected block number error, got %q", err)
 	}
 
 	header = makeHeader(chain.Genesis(), statedb)
-	err = ValidateHeader(pow, header, chain.Genesis(), false, false)
+	err = ValidateHeader(pow, types.NewHeader(header), chain.Genesis(), false, false)
 	if err == BlockNumberErr {
 		t.Errorf("didn't expect block number error")
 	}
diff --git a/core/chain_makers.go b/core/chain_makers.go
index b009e0c28c..20d0511a96 100644
--- a/core/chain_makers.go
+++ b/core/chain_makers.go
@@ -49,7 +49,7 @@ type BlockGen struct {
 	i       int
 	parent  *types.Block
 	chain   []*types.Block
-	header  *types.Header
+	header  *types.RawHeader
 	statedb *state.StateDB
 
 	coinbase *state.StateObject
@@ -89,12 +89,12 @@ func (b *BlockGen) AddTx(tx *types.Transaction) {
 	if b.coinbase == nil {
 		b.SetCoinbase(common.Address{})
 	}
-	_, gas, err := ApplyMessage(NewEnv(b.statedb, nil, tx, b.header), tx, b.coinbase)
+	_, gas, err := ApplyMessage(NewEnv(b.statedb, nil, tx, types.NewHeader(b.header)), tx, b.coinbase)
 	if err != nil {
 		panic(err)
 	}
 	b.statedb.SyncIntermediate()
-	b.header.GasUsed.Add(b.header.GasUsed, gas)
+	b.header.GasUsed = new(big.Int).Add(b.header.GasUsed, gas)
 	receipt := types.NewReceipt(b.statedb.Root().Bytes(), b.header.GasUsed)
 	logs := b.statedb.GetLogs(tx.Hash())
 	receipt.SetLogs(logs)
@@ -145,12 +145,12 @@ func (b *BlockGen) PrevBlock(index int) *types.Block {
 func GenerateChain(parent *types.Block, db common.Database, n int, gen func(int, *BlockGen)) []*types.Block {
 	statedb := state.New(parent.Root(), db)
 	blocks := make(types.Blocks, n)
-	genblock := func(i int, h *types.Header) *types.Block {
+	genblock := func(i int, h *types.RawHeader) *types.Block {
 		b := &BlockGen{parent: parent, i: i, chain: blocks, header: h, statedb: statedb}
 		if gen != nil {
 			gen(i, b)
 		}
-		AccumulateRewards(statedb, h, b.uncles)
+		AccumulateRewards(statedb, types.NewHeader(h), b.uncles)
 		statedb.SyncIntermediate()
 		h.Root = statedb.Root()
 		return types.NewBlock(h, b.txs, b.uncles, b.receipts)
@@ -165,14 +165,14 @@ func GenerateChain(parent *types.Block, db common.Database, n int, gen func(int,
 	return blocks
 }
 
-func makeHeader(parent *types.Block, state *state.StateDB) *types.Header {
+func makeHeader(parent *types.Block, state *state.StateDB) *types.RawHeader {
 	var time *big.Int
 	if parent.Time() == nil {
 		time = big.NewInt(10)
 	} else {
 		time = new(big.Int).Add(parent.Time(), big.NewInt(10)) // block time is fixed at 10 seconds
 	}
-	return &types.Header{
+	return &types.RawHeader{
 		Root:       state.Root(),
 		ParentHash: parent.Hash(),
 		Coinbase:   parent.Coinbase(),
diff --git a/core/chain_makers_test.go b/core/chain_makers_test.go
index 1c868624df..31e3ff29a4 100644
--- a/core/chain_makers_test.go
+++ b/core/chain_makers_test.go
@@ -66,12 +66,12 @@ func ExampleGenerateChain() {
 			gen.SetExtra([]byte("yeehaw"))
 		case 3:
 			// Block 4 includes blocks 2 and 3 as uncle headers (with modified extra data).
-			b2 := gen.PrevBlock(1).Header()
+			b2 := gen.PrevBlock(1).Header().Raw()
 			b2.Extra = []byte("foo")
-			gen.AddUncle(b2)
-			b3 := gen.PrevBlock(2).Header()
+			gen.AddUncle(types.NewHeader(b2))
+			b3 := gen.PrevBlock(2).Header().Raw()
 			b3.Extra = []byte("foo")
-			gen.AddUncle(b3)
+			gen.AddUncle(types.NewHeader(b3))
 		}
 	})
 
diff --git a/core/chain_manager.go b/core/chain_manager.go
index 745b270f7c..381d009f99 100644
--- a/core/chain_manager.go
+++ b/core/chain_manager.go
@@ -207,7 +207,7 @@ func (bc *ChainManager) recover() bool {
 	if len(data) != 0 {
 		block := bc.GetBlock(common.BytesToHash(data))
 		if block != nil {
-			if err := WriteHead(bc.chainDb, block); err != nil {
+			if err := WriteHeadBlockMeta(bc.chainDb, block); err != nil {
 				glog.Fatalf("failed to write database head: %v", err)
 			}
 			bc.currentBlock = block
@@ -219,7 +219,7 @@ func (bc *ChainManager) recover() bool {
 }
 
 func (bc *ChainManager) setLastState() error {
-	head := GetHeadHash(bc.chainDb)
+	head := GetHeadBlockHash(bc.chainDb)
 	if head != (common.Hash{}) {
 		block := bc.GetBlock(head)
 		if block != nil {
@@ -315,7 +315,7 @@ func (self *ChainManager) ExportN(w io.Writer, first uint64, last uint64) error
 // insert injects a block into the current chain block chain. Note, this function
 // assumes that the `mu` mutex is held!
 func (bc *ChainManager) insert(block *types.Block) {
-	err := WriteHead(bc.chainDb, block)
+	err := WriteHeadBlockMeta(bc.chainDb, block)
 	if err != nil {
 		glog.Fatal("db write fail:", err)
 	}
@@ -451,11 +451,11 @@ func (self *ChainManager) GetBlockHashesFromHash(hash common.Hash, max uint64) [
 	// Iterate the headers until enough is collected or the genesis reached
 	chain := make([]common.Hash, 0, max)
 	for i := uint64(0); i < max; i++ {
-		if header = self.GetHeader(header.ParentHash); header == nil {
+		if header = self.GetHeader(header.ParentHash()); header == nil {
 			break
 		}
 		chain = append(chain, header.Hash())
-		if header.Number.Cmp(common.Big0) <= 0 {
+		if header.Number().Cmp(common.Big0) <= 0 {
 			break
 		}
 	}
@@ -531,6 +531,22 @@ const (
 	SideStatTy
 )
 
+/*
+// WriteHeader inserts a potentially new header into the database, updating the
+// head-header-hash index too if greater than the previous.
+func (self *ChainManager) WriteHeader(db common.Database, header *types.Header) error {
+	self.wg.Add(1)
+	defer self.wg.Done()
+
+	// Store the header into the database
+	if err := WriteHeader(self.chainDb, header); err != nil {
+		glog.Fatalf("failed to write header: %v", err)
+		return err
+	}
+	// If the header's higher than our previous head, update
+	if header.
+}*/
+
 // WriteBlock writes the block to the chain (or pending queue)
 func (self *ChainManager) WriteBlock(block *types.Block, queued bool) (status writeStatus, err error) {
 	self.wg.Add(1)
diff --git a/core/chain_manager_test.go b/core/chain_manager_test.go
index 97e7cacdc9..8692bb97a2 100644
--- a/core/chain_manager_test.go
+++ b/core/chain_manager_test.go
@@ -369,7 +369,7 @@ func (bproc) Process(*types.Block) (state.Logs, types.Receipts, error) { return
 func makeChainWithDiff(genesis *types.Block, d []int, seed byte) []*types.Block {
 	var chain []*types.Block
 	for i, difficulty := range d {
-		header := &types.Header{
+		header := &types.RawHeader{
 			Coinbase:   common.Address{seed},
 			Number:     big.NewInt(int64(i + 1)),
 			Difficulty: big.NewInt(int64(difficulty)),
@@ -379,7 +379,7 @@ func makeChainWithDiff(genesis *types.Block, d []int, seed byte) []*types.Block
 		} else {
 			header.ParentHash = chain[i-1].Hash()
 		}
-		block := types.NewBlockWithHeader(header)
+		block := types.NewBlockWithRawHeader(header)
 		chain = append(chain, block)
 	}
 	return chain
diff --git a/core/chain_util.go b/core/chain_util.go
index c12bdda75d..185e04a135 100644
--- a/core/chain_util.go
+++ b/core/chain_util.go
@@ -29,7 +29,8 @@ import (
 )
 
 var (
-	headKey = []byte("LastBlock")
+	headHeaderKey = []byte("LastHeader")
+	headBlockKey  = []byte("LastBlock")
 
 	headerHashPre = []byte("header-hash-")
 	bodyHashPre   = []byte("body-hash-")
@@ -131,9 +132,22 @@ func GetHashByNumber(db common.Database, number uint64) common.Hash {
 	return common.BytesToHash(data)
 }
 
-// GetHeadHash retrieves the hash of the current canonical head block.
-func GetHeadHash(db common.Database) common.Hash {
-	data, _ := db.Get(headKey)
+// GetHeadHeaderHash retrieves the hash of the current canonical head block's
+// header. The different between this and GetHeadBlockHash is that whereas the
+// last block hash is only updated upon a full block import, the last header
+// hash is updated already at header import, allowing head tracking for the
+// fast synchronization mechanism.
+func GetHeadHeaderHash(db common.Database) common.Hash {
+	data, _ := db.Get(headHeaderKey)
+	if len(data) == 0 {
+		return common.Hash{}
+	}
+	return common.BytesToHash(data)
+}
+
+// GetHeadBlockHash retrieves the hash of the current canonical head block.
+func GetHeadBlockHash(db common.Database) common.Hash {
+	data, _ := db.Get(headBlockKey)
 	if len(data) == 0 {
 		return common.Hash{}
 	}
@@ -232,14 +246,23 @@ func WriteCanonNumber(db common.Database, hash common.Hash, number uint64) error
 	return nil
 }
 
-// WriteHead updates the head block of the chain database.
-func WriteHead(db common.Database, block *types.Block) error {
-	if err := WriteCanonNumber(db, block.Hash(), block.NumberU64()); err != nil {
-		glog.Fatalf("failed to store canonical number into database: %v", err)
+// WriteHeadBlockMeta stores the head header's hash.
+func WriteHeadHeaderHash(db common.Database, header *types.Header) error {
+	if err := db.Put(headHeaderKey, header.Hash().Bytes()); err != nil {
+		glog.Fatalf("failed to store last header's hash into database: %v", err)
 		return err
 	}
-	if err := db.Put(headKey, block.Hash().Bytes()); err != nil {
-		glog.Fatalf("failed to store last block into database: %v", err)
+	return nil
+}
+
+// WriteHeadBlockMeta stores the head block's metadata (number and hash).
+func WriteHeadBlockMeta(db common.Database, block *types.Block) error {
+	if err := WriteCanonNumber(db, block.Hash(), block.NumberU64()); err != nil {
+		glog.Fatalf("failed to store last block's canonical number into database: %v", err)
+		return err
+	}
+	if err := db.Put(headBlockKey, block.Hash().Bytes()); err != nil {
+		glog.Fatalf("failed to store last block's hash into database: %v", err)
 		return err
 	}
 	return nil
diff --git a/core/genesis.go b/core/genesis.go
index 6fbc671b06..5ba09e477b 100644
--- a/core/genesis.go
+++ b/core/genesis.go
@@ -71,7 +71,8 @@ func WriteGenesisBlock(chainDb common.Database, reader io.Reader) (*types.Block,
 	statedb.SyncObjects()
 
 	difficulty := common.String2Big(genesis.Difficulty)
-	block := types.NewBlock(&types.Header{
+
+	header := &types.RawHeader{
 		Nonce:      types.EncodeNonce(common.String2Big(genesis.Nonce).Uint64()),
 		Time:       common.String2Big(genesis.Timestamp),
 		ParentHash: common.HexToHash(genesis.ParentHash),
@@ -81,7 +82,8 @@ func WriteGenesisBlock(chainDb common.Database, reader io.Reader) (*types.Block,
 		MixDigest:  common.HexToHash(genesis.Mixhash),
 		Coinbase:   common.HexToAddress(genesis.Coinbase),
 		Root:       statedb.Root(),
-	}, nil, nil, nil)
+	}
+	block := types.NewBlock(header, nil, nil, nil)
 	block.Td = difficulty
 
 	if block := GetBlockByHash(chainDb, block.Hash()); block != nil {
@@ -99,7 +101,7 @@ func WriteGenesisBlock(chainDb common.Database, reader io.Reader) (*types.Block,
 	if err != nil {
 		return nil, err
 	}
-	err = WriteHead(chainDb, block)
+	err = WriteHeadBlockMeta(chainDb, block)
 	if err != nil {
 		return nil, err
 	}
@@ -115,11 +117,13 @@ func GenesisBlockForTesting(db common.Database, addr common.Address, balance *bi
 	obj.SetBalance(balance)
 	statedb.SyncObjects()
 	statedb.Sync()
-	block := types.NewBlock(&types.Header{
+
+	header := &types.RawHeader{
 		Difficulty: params.GenesisDifficulty,
 		GasLimit:   params.GenesisGasLimit,
 		Root:       statedb.Root(),
-	}, nil, nil, nil)
+	}
+	block := types.NewBlock(header, nil, nil, nil)
 	block.Td = params.GenesisDifficulty
 	return block
 }
diff --git a/core/types/block.go b/core/types/block.go
index 558b46e010..6dd3718820 100644
--- a/core/types/block.go
+++ b/core/types/block.go
@@ -18,9 +18,6 @@
 package types
 
 import (
-	"bytes"
-	"encoding/binary"
-	"encoding/json"
 	"fmt"
 	"io"
 	"math/big"
@@ -29,94 +26,11 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/crypto/sha3"
 	"github.com/ethereum/go-ethereum/rlp"
 )
 
-// A BlockNonce is a 64-bit hash which proves (combined with the
-// mix-hash) that a suffcient amount of computation has been carried
-// out on a block.
-type BlockNonce [8]byte
-
-func EncodeNonce(i uint64) BlockNonce {
-	var n BlockNonce
-	binary.BigEndian.PutUint64(n[:], i)
-	return n
-}
-
-func (n BlockNonce) Uint64() uint64 {
-	return binary.BigEndian.Uint64(n[:])
-}
-
-type Header struct {
-	ParentHash  common.Hash    // Hash to the previous block
-	UncleHash   common.Hash    // Uncles of this block
-	Coinbase    common.Address // The coin base address
-	Root        common.Hash    // Block Trie state
-	TxHash      common.Hash    // Tx sha
-	ReceiptHash common.Hash    // Receipt sha
-	Bloom       Bloom          // Bloom
-	Difficulty  *big.Int       // Difficulty for the current block
-	Number      *big.Int       // The block number
-	GasLimit    *big.Int       // Gas limit
-	GasUsed     *big.Int       // Gas used
-	Time        *big.Int       // Creation time
-	Extra       []byte         // Extra data
-	MixDigest   common.Hash    // for quick difficulty verification
-	Nonce       BlockNonce
-}
-
-func (h *Header) Hash() common.Hash {
-	return rlpHash(h)
-}
-
-func (h *Header) HashNoNonce() common.Hash {
-	return rlpHash([]interface{}{
-		h.ParentHash,
-		h.UncleHash,
-		h.Coinbase,
-		h.Root,
-		h.TxHash,
-		h.ReceiptHash,
-		h.Bloom,
-		h.Difficulty,
-		h.Number,
-		h.GasLimit,
-		h.GasUsed,
-		h.Time,
-		h.Extra,
-	})
-}
-
-func (h *Header) UnmarshalJSON(data []byte) error {
-	var ext struct {
-		ParentHash string
-		Coinbase   string
-		Difficulty string
-		GasLimit   string
-		Time       *big.Int
-		Extra      string
-	}
-	dec := json.NewDecoder(bytes.NewReader(data))
-	if err := dec.Decode(&ext); err != nil {
-		return err
-	}
-
-	h.ParentHash = common.HexToHash(ext.ParentHash)
-	h.Coinbase = common.HexToAddress(ext.Coinbase)
-	h.Difficulty = common.String2Big(ext.Difficulty)
-	h.Time = ext.Time
-	h.Extra = []byte(ext.Extra)
-	return nil
-}
-
-func rlpHash(x interface{}) (h common.Hash) {
-	hw := sha3.NewKeccak256()
-	rlp.Encode(hw, x)
-	hw.Sum(h[:0])
-	return h
-}
-
+// Header is the main Ethereum block, containing all of the block data belonging
+// to the consensus protocol, as well as a few added fields for the implementation.
 type Block struct {
 	header       *Header
 	uncles       []*Header
@@ -124,7 +38,6 @@ type Block struct {
 	receipts     Receipts
 
 	// caches
-	hash atomic.Value
 	size atomic.Value
 
 	// Td is used by package core to store the total difficulty
@@ -169,69 +82,56 @@ var (
 // The values of TxHash, UncleHash, ReceiptHash and Bloom in header
 // are ignored and set to values derived from the given txs, uncles
 // and receipts.
-func NewBlock(header *Header, txs []*Transaction, uncles []*Header, receipts []*Receipt) *Block {
-	b := &Block{header: copyHeader(header), Td: new(big.Int)}
+func NewBlock(header *RawHeader, txs []*Transaction, uncles []*Header, receipts []*Receipt) *Block {
+	head := header.Copy()
 
 	// TODO: panic if len(txs) != len(receipts)
 	if len(txs) == 0 {
-		b.header.TxHash = emptyRootHash
+		head.TxHash = emptyRootHash
 	} else {
-		b.header.TxHash = DeriveSha(Transactions(txs))
-		b.transactions = make(Transactions, len(txs))
-		copy(b.transactions, txs)
+		head.TxHash = DeriveSha(Transactions(txs))
 	}
+	txsCopy := make(Transactions, len(txs))
+	copy(txsCopy, txs)
 
 	if len(receipts) == 0 {
-		b.header.ReceiptHash = emptyRootHash
+		head.ReceiptHash = emptyRootHash
 	} else {
-		b.header.ReceiptHash = DeriveSha(Receipts(receipts))
-		b.header.Bloom = CreateBloom(receipts)
-		b.receipts = make([]*Receipt, len(receipts))
-		copy(b.receipts, receipts)
+		head.ReceiptHash = DeriveSha(Receipts(receipts))
+		head.Bloom = CreateBloom(receipts)
 	}
+	receiptsCopy := make([]*Receipt, len(receipts))
+	copy(receiptsCopy, receipts)
 
 	if len(uncles) == 0 {
-		b.header.UncleHash = emptyUncleHash
+		head.UncleHash = emptyUncleHash
 	} else {
-		b.header.UncleHash = CalcUncleHash(uncles)
-		b.uncles = make([]*Header, len(uncles))
-		for i := range uncles {
-			b.uncles[i] = copyHeader(uncles[i])
-		}
+		head.UncleHash = CalcUncleHash(uncles)
+	}
+	unclesCopy := make([]*Header, len(uncles))
+	for i := range uncles {
+		unclesCopy[i] = uncles[i].Copy()
+	}
+	// Assemble and return an immutable block
+	return &Block{
+		header:       &Header{rawHeader: *head},
+		transactions: txsCopy,
+		receipts:     receiptsCopy,
+		uncles:       unclesCopy,
+		Td:           new(big.Int),
 	}
-
-	return b
 }
 
-// NewBlockWithHeader creates a block with the given header data. The
-// header data is copied, changes to header and to the field values
-// will not affect the block.
+// NewBlockWithRawHeader creates a block with the given header data. The header
+// data is copied, changes to header and to the field values will not affect
+// the block.
+func NewBlockWithRawHeader(raw *RawHeader) *Block {
+	return &Block{header: NewHeader(raw)}
+}
+
+// NewBlockWithHeader creates a block with the given immutable header.
 func NewBlockWithHeader(header *Header) *Block {
-	return &Block{header: copyHeader(header)}
-}
-
-func copyHeader(h *Header) *Header {
-	cpy := *h
-	if cpy.Time = new(big.Int); h.Time != nil {
-		cpy.Time.Set(h.Time)
-	}
-	if cpy.Difficulty = new(big.Int); h.Difficulty != nil {
-		cpy.Difficulty.Set(h.Difficulty)
-	}
-	if cpy.Number = new(big.Int); h.Number != nil {
-		cpy.Number.Set(h.Number)
-	}
-	if cpy.GasLimit = new(big.Int); h.GasLimit != nil {
-		cpy.GasLimit.Set(h.GasLimit)
-	}
-	if cpy.GasUsed = new(big.Int); h.GasUsed != nil {
-		cpy.GasUsed.Set(h.GasUsed)
-	}
-	if len(h.Extra) > 0 {
-		cpy.Extra = make([]byte, len(h.Extra))
-		copy(cpy.Extra, h.Extra)
-	}
-	return &cpy
+	return &Block{header: header}
 }
 
 func (b *Block) ValidateFields() error {
@@ -304,29 +204,28 @@ func (b *Block) Transaction(hash common.Hash) *Transaction {
 	return nil
 }
 
-func (b *Block) Number() *big.Int     { return new(big.Int).Set(b.header.Number) }
-func (b *Block) GasLimit() *big.Int   { return new(big.Int).Set(b.header.GasLimit) }
-func (b *Block) GasUsed() *big.Int    { return new(big.Int).Set(b.header.GasUsed) }
-func (b *Block) Difficulty() *big.Int { return new(big.Int).Set(b.header.Difficulty) }
-func (b *Block) Time() *big.Int       { return new(big.Int).Set(b.header.Time) }
+func (b *Block) Number() *big.Int     { return b.header.Number() }
+func (b *Block) GasLimit() *big.Int   { return b.header.GasLimit() }
+func (b *Block) GasUsed() *big.Int    { return b.header.GasUsed() }
+func (b *Block) Difficulty() *big.Int { return b.header.Difficulty() }
+func (b *Block) Time() *big.Int       { return b.header.Time() }
 
-func (b *Block) NumberU64() uint64        { return b.header.Number.Uint64() }
-func (b *Block) MixDigest() common.Hash   { return b.header.MixDigest }
-func (b *Block) Nonce() uint64            { return binary.BigEndian.Uint64(b.header.Nonce[:]) }
-func (b *Block) Bloom() Bloom             { return b.header.Bloom }
-func (b *Block) Coinbase() common.Address { return b.header.Coinbase }
-func (b *Block) Root() common.Hash        { return b.header.Root }
-func (b *Block) ParentHash() common.Hash  { return b.header.ParentHash }
-func (b *Block) TxHash() common.Hash      { return b.header.TxHash }
-func (b *Block) ReceiptHash() common.Hash { return b.header.ReceiptHash }
-func (b *Block) UncleHash() common.Hash   { return b.header.UncleHash }
-func (b *Block) Extra() []byte            { return common.CopyBytes(b.header.Extra) }
+func (b *Block) NumberU64() uint64        { return b.header.Number().Uint64() }
+func (b *Block) MixDigest() common.Hash   { return b.header.MixDigest() }
+func (b *Block) Nonce() uint64            { return b.header.Nonce().Uint64() }
+func (b *Block) Bloom() Bloom             { return b.header.Bloom() }
+func (b *Block) Coinbase() common.Address { return b.header.Coinbase() }
+func (b *Block) Root() common.Hash        { return b.header.Root() }
+func (b *Block) ParentHash() common.Hash  { return b.header.ParentHash() }
+func (b *Block) TxHash() common.Hash      { return b.header.TxHash() }
+func (b *Block) ReceiptHash() common.Hash { return b.header.ReceiptHash() }
+func (b *Block) UncleHash() common.Hash   { return b.header.UncleHash() }
+func (b *Block) Extra() []byte            { return b.header.Extra() }
 
-func (b *Block) Header() *Header { return copyHeader(b.header) }
+func (b *Block) Header() *Header { return b.header }
 
-func (b *Block) HashNoNonce() common.Hash {
-	return b.header.HashNoNonce()
-}
+func (b *Block) HashNoNonce() common.Hash { return b.header.HashNoNonce() }
+func (b *Block) Hash() common.Hash        { return b.header.Hash() }
 
 func (b *Block) Size() common.StorageSize {
 	if size := b.size.Load(); size != nil {
@@ -352,11 +251,11 @@ func CalcUncleHash(uncles []*Header) common.Hash {
 // 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 uint64, mixDigest common.Hash) *Block {
-	cpy := *b.header
-	binary.BigEndian.PutUint64(cpy.Nonce[:], nonce)
-	cpy.MixDigest = mixDigest
+	header := b.header.Raw()
+	header.Nonce = EncodeNonce(nonce)
+	header.MixDigest = mixDigest
 	return &Block{
-		header:       &cpy,
+		header:       &Header{rawHeader: *header},
 		transactions: b.transactions,
 		receipts:     b.receipts,
 		uncles:       b.uncles,
@@ -367,28 +266,19 @@ func (b *Block) WithMiningResult(nonce uint64, mixDigest common.Hash) *Block {
 // WithBody returns a new block with the given transaction and uncle contents.
 func (b *Block) WithBody(transactions []*Transaction, uncles []*Header) *Block {
 	block := &Block{
-		header:       copyHeader(b.header),
+		header:       b.header.Copy(),
 		transactions: make([]*Transaction, len(transactions)),
 		uncles:       make([]*Header, len(uncles)),
 	}
 	copy(block.transactions, transactions)
 	for i := range uncles {
-		block.uncles[i] = copyHeader(uncles[i])
+		block.uncles[i] = uncles[i].Copy()
 	}
 	return block
 }
 
 // Implement pow.Block
 
-func (b *Block) Hash() common.Hash {
-	if hash := b.hash.Load(); hash != nil {
-		return hash.(common.Hash)
-	}
-	v := rlpHash(b.header)
-	b.hash.Store(v)
-	return v
-}
-
 func (b *Block) String() string {
 	str := fmt.Sprintf(`Block(#%v): Size: %v TD: %v {
 MinerHash: %x
@@ -402,27 +292,6 @@ Uncles:
 	return str
 }
 
-func (h *Header) String() string {
-	return fmt.Sprintf(`Header(%x):
-[
-	ParentHash:	    %x
-	UncleHash:	    %x
-	Coinbase:	    %x
-	Root:		    %x
-	TxSha		    %x
-	ReceiptSha:	    %x
-	Bloom:		    %x
-	Difficulty:	    %v
-	Number:		    %v
-	GasLimit:	    %v
-	GasUsed:	    %v
-	Time:		    %v
-	Extra:		    %s
-	MixDigest:      %x
-	Nonce:		    %x
-]`, h.Hash(), h.ParentHash, h.UncleHash, h.Coinbase, h.Root, h.TxHash, h.ReceiptHash, h.Bloom, h.Difficulty, h.Number, h.GasLimit, h.GasUsed, h.Time, h.Extra, h.MixDigest, h.Nonce)
-}
-
 type Blocks []*Block
 
 type BlockBy func(b1, b2 *Block) bool
@@ -446,4 +315,4 @@ func (self blockSorter) Swap(i, j int) {
 }
 func (self blockSorter) Less(i, j int) bool { return self.by(self.blocks[i], self.blocks[j]) }
 
-func Number(b1, b2 *Block) bool { return b1.header.Number.Cmp(b2.header.Number) < 0 }
+func Number(b1, b2 *Block) bool { return b1.header.Number().Cmp(b2.header.Number()) < 0 }
diff --git a/core/types/header.go b/core/types/header.go
new file mode 100644
index 0000000000..2dddeadd58
--- /dev/null
+++ b/core/types/header.go
@@ -0,0 +1,309 @@
+// 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/>.
+
+// Contains the block header type and related methods.
+
+package types
+
+import (
+	"bytes"
+	"encoding/binary"
+	"encoding/json"
+	"fmt"
+	"io"
+	"math/big"
+	"sync/atomic"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto/sha3"
+	"github.com/ethereum/go-ethereum/rlp"
+)
+
+// A BlockNonce is a 64-bit hash which proves (combined with the
+// mix-hash) that a suffcient amount of computation has been carried
+// out on a block.
+type BlockNonce [8]byte
+
+func EncodeNonce(i uint64) BlockNonce {
+	var n BlockNonce
+	binary.BigEndian.PutUint64(n[:], i)
+	return n
+}
+
+func (n BlockNonce) Uint64() uint64 {
+	return binary.BigEndian.Uint64(n[:])
+}
+
+// RawHeader is the base consensus header used by the Ethereum system, which
+// contains only the bare essential fields defined by the consensus protocol.
+//
+// This structure is mutable, and can be used to create an immutable header
+// used throughout the codebase. Do not pass this structure around, only use
+// to aid in new header construction or data query from an existing header.
+type RawHeader struct {
+	ParentHash  common.Hash    // Hash of the previous block in the chain
+	UncleHash   common.Hash    // Hash of the uncles contained in this block
+	Coinbase    common.Address // Owner address of the block (miner)
+	Root        common.Hash    // Merkle-Patricia state trie root hash
+	TxHash      common.Hash    // Hash of the transactions contained in this block
+	ReceiptHash common.Hash    // Hash of the transactions receipts contained in this block
+	Bloom       Bloom          // Bloom filter for the event logs in the block
+	Difficulty  *big.Int       // Proof-of-work difficulty of this block
+	Number      *big.Int       // Index number of the block within the chain
+	GasLimit    *big.Int       // Maximum gas allowance for this block
+	GasUsed     *big.Int       // Amount of gas actually used in this block
+	Time        *big.Int       // Creation timestamp of this block
+	Extra       []byte         // Extra data inserted into the block by the miner
+	MixDigest   common.Hash    // Miner mix digest for quick difficulty verification
+	Nonce       BlockNonce     // Proof-of-work nonce of the block
+}
+
+// hash calculates the nonce-inclusive hash of the header. As the raw header is
+// mutable, this hasher cannot cache its expensive operation, hence it's private
+// and users are required to use the immutable Header's Hash method.
+func (h *RawHeader) hash() common.Hash {
+	return rlpHash(h)
+}
+
+// hashNoNonce calculates the miner hash of the header (no mix digest or nonce).
+// Similarly to the hash method, as the raw header is mutable, this hasher also
+// cannot cache its expensive operation, hence it's private and users are asked
+// to use the immutable Header's HashNoNonce method.
+func (h *RawHeader) hashNoNonce() common.Hash {
+	return rlpHash([]interface{}{
+		h.ParentHash,
+		h.UncleHash,
+		h.Coinbase,
+		h.Root,
+		h.TxHash,
+		h.ReceiptHash,
+		h.Bloom,
+		h.Difficulty,
+		h.Number,
+		h.GasLimit,
+		h.GasUsed,
+		h.Time,
+		h.Extra,
+	})
+}
+
+// Copy creates a deep copy of a raw header.
+func (h *RawHeader) Copy() *RawHeader {
+	cpy := *h
+	if cpy.Difficulty = new(big.Int); h.Difficulty != nil {
+		cpy.Difficulty.Set(h.Difficulty)
+	}
+	if cpy.Number = new(big.Int); h.Number != nil {
+		cpy.Number.Set(h.Number)
+	}
+	if cpy.GasLimit = new(big.Int); h.GasLimit != nil {
+		cpy.GasLimit.Set(h.GasLimit)
+	}
+	if cpy.GasUsed = new(big.Int); h.GasUsed != nil {
+		cpy.GasUsed.Set(h.GasUsed)
+	}
+	if cpy.Time = new(big.Int); h.Time != nil {
+		cpy.Time.Set(h.Time)
+	}
+	if len(h.Extra) > 0 {
+		cpy.Extra = common.CopyBytes(h.Extra)
+	}
+	return &cpy
+}
+
+// Header is the immutable Ethereum block header, containing all of the metadata
+// related to a chain block, and some additional helper fields, caches.
+type Header struct {
+	rawHeader RawHeader // Base header fields part of the consensus protocol
+
+	hashNoNonce   atomic.Value // Cached hash of the header without the nonce
+	hashWithNonce atomic.Value // Cached hash of the header with the nonce
+	rlpSize       atomic.Value // Size of the header in RLP encoded format
+}
+
+// NewHeader creates an immutable header from a mutable raw header.
+func NewHeader(raw *RawHeader) *Header {
+	return &Header{
+		rawHeader: *raw.Copy(),
+	}
+}
+
+// Raw creates and returns a mutable deep copy of the raw consensus header.
+func (h *Header) Raw() *RawHeader {
+	return h.rawHeader.Copy()
+}
+
+// ParentHash retrieves the hash of this block's parent in the blockchain.
+func (h *Header) ParentHash() common.Hash { return h.rawHeader.ParentHash }
+
+// UncleHash retrieves the hash of the uncle blocks contained within this block.
+func (h *Header) UncleHash() common.Hash { return h.rawHeader.UncleHash }
+
+// Coinbase retrieves the account owning this block (i.e. miner).
+func (h *Header) Coinbase() common.Address { return h.rawHeader.Coinbase }
+
+// Root retrieves the root hash of the Merkle-Patricia state trie formed.
+func (h *Header) Root() common.Hash { return h.rawHeader.Root }
+
+// TxHash retrieves the hash of the transactions contained within this block.
+func (h *Header) TxHash() common.Hash { return h.rawHeader.TxHash }
+
+// ReceiptHash retrieves the hash of the transaction receipts contained within.
+func (h *Header) ReceiptHash() common.Hash { return h.rawHeader.ReceiptHash }
+
+// Bloom retrieves the bloom filter of the event logs contained within.
+func (h *Header) Bloom() Bloom { return h.rawHeader.Bloom }
+
+// Difficulty retrieves the proof-of-work difficulty of this block.
+func (h *Header) Difficulty() *big.Int { return new(big.Int).Set(h.rawHeader.Difficulty) }
+
+// Number retrieves the index/number of the block within the chain.
+func (h *Header) Number() *big.Int { return new(big.Int).Set(h.rawHeader.Number) }
+
+// GasLimit retrieves the maximum gas allowance for this block.
+func (h *Header) GasLimit() *big.Int { return new(big.Int).Set(h.rawHeader.GasLimit) }
+
+// GasUsed retrieves the amount of gas actually used in this block.
+func (h *Header) GasUsed() *big.Int { return new(big.Int).Set(h.rawHeader.GasUsed) }
+
+// Time retrieves the creation timestamp of this block.
+func (h *Header) Time() *big.Int { return new(big.Int).Set(h.rawHeader.Time) }
+
+// Extra retrieves the extra data inserted into the block by the miner.
+func (h *Header) Extra() []byte {
+	return common.CopyBytes(h.rawHeader.Extra)
+}
+
+// MixDigest retrieves the miner mix digest for quick difficulty verification.
+func (h *Header) MixDigest() common.Hash { return h.rawHeader.MixDigest }
+
+// Nonce retrieves the proof-of-work nonce of the block.
+func (h *Header) Nonce() BlockNonce { return h.rawHeader.Nonce }
+
+// RlpSize retrieves the RLP encoded size of the header, calculating and caching
+// if it unknown.
+func (h *Header) RlpSize() common.StorageSize {
+	if size := h.rlpSize.Load(); size != nil && size.(common.StorageSize).Int64() != 0 {
+		return size.(common.StorageSize)
+	}
+	counter := writeCounter(0)
+	rlp.Encode(&counter, h.rawHeader)
+
+	h.rlpSize.Store(common.StorageSize(counter))
+	return common.StorageSize(counter)
+}
+
+// Hash retrieves the nonce-inclusive hash of the header, calculating and caching
+// it if unknown.
+func (h *Header) Hash() common.Hash {
+	if hash := h.hashWithNonce.Load(); hash != nil && hash.(common.Hash) != (common.Hash{}) {
+		return hash.(common.Hash)
+	}
+	hash := h.rawHeader.hash()
+	h.hashWithNonce.Store(hash)
+	return hash
+}
+
+// HashNoNonce retrieves the miner hash of the header (no mix digest or nonce),
+// calculating and caching it if unknown.
+func (h *Header) HashNoNonce() common.Hash {
+	if hash := h.hashNoNonce.Load(); hash != nil && hash.(common.Hash) != (common.Hash{}) {
+		return hash.(common.Hash)
+	}
+	hash := h.rawHeader.hashNoNonce()
+	h.hashNoNonce.Store(hash)
+	return hash
+}
+
+// DecodeRLP implements the rlp.Decoder interface, deserializing a raw header
+// from an RLP Data stream.
+func (h *Header) DecodeRLP(s *rlp.Stream) error {
+	// Reset any previously cached fields
+	h.hashNoNonce.Store(common.Hash{})
+	h.hashWithNonce.Store(common.Hash{})
+	h.rlpSize.Store(common.StorageSize(0))
+
+	// Fill in the real RLP encoded size of the header
+	_, size, _ := s.Kind()
+	h.rlpSize.Store(common.StorageSize(rlp.ListSize(size)))
+
+	// Decode the RLP encoded raw header
+	return s.Decode(&h.rawHeader)
+}
+
+// EncodeRLP implements the rlp.Encoder interface, serializing a raw header into
+// and RLP data stream.
+func (h *Header) EncodeRLP(w io.Writer) error {
+	return rlp.Encode(w, h.rawHeader)
+}
+
+func (h *Header) UnmarshalJSON(data []byte) error {
+	var ext struct {
+		ParentHash string
+		Coinbase   string
+		Difficulty string
+		GasLimit   string
+		Time       *big.Int
+		Extra      string
+	}
+	dec := json.NewDecoder(bytes.NewReader(data))
+	if err := dec.Decode(&ext); err != nil {
+		return err
+	}
+	h.rawHeader.ParentHash = common.HexToHash(ext.ParentHash)
+	h.rawHeader.Coinbase = common.HexToAddress(ext.Coinbase)
+	h.rawHeader.Difficulty = common.String2Big(ext.Difficulty)
+	h.rawHeader.Time = ext.Time
+	h.rawHeader.Extra = []byte(ext.Extra)
+
+	return nil
+}
+
+// Copy creates a deep copy of a header.
+func (h *Header) Copy() *Header {
+	cpy := new(Header)
+	cpy.rawHeader = *h.rawHeader.Copy()
+	return cpy
+}
+
+// String implements the fmt.Stringer interface, formatting a header into a string.
+func (h *Header) String() string {
+	return fmt.Sprintf(`Header(%x):
+[
+	ParentHash:	    %x
+	UncleHash:	    %x
+	Coinbase:	    %x
+	Root:		    %x
+	TxSha:		    %x
+	ReceiptSha:	    %x
+	Bloom:		    %x
+	Difficulty:	    %v
+	Number:		    %v
+	GasLimit:	    %v
+	GasUsed:	    %v
+	Time:		    %v
+	Extra:		    %s
+	MixDigest:	    %x
+	Nonce:		    %x
+]`, h.Hash(), h.ParentHash(), h.UncleHash(), h.Coinbase(), h.Root(), h.TxHash(), h.ReceiptHash(), h.Bloom(), h.Difficulty(), h.Number(), h.GasLimit(), h.GasUsed(), h.Time(), h.Extra(), h.MixDigest(), h.Nonce())
+}
+
+func rlpHash(x interface{}) (h common.Hash) {
+	hw := sha3.NewKeccak256()
+	rlp.Encode(hw, x)
+	hw.Sum(h[:0])
+	return h
+}
diff --git a/core/vm_env.go b/core/vm_env.go
index a08f024fe7..fb373ccc23 100644
--- a/core/vm_env.go
+++ b/core/vm_env.go
@@ -27,7 +27,7 @@ import (
 
 type VMEnv struct {
 	state  *state.StateDB
-	header *types.Header
+	header *types.RawHeader
 	msg    Message
 	depth  int
 	chain  *ChainManager
@@ -40,7 +40,7 @@ func NewEnv(state *state.StateDB, chain *ChainManager, msg Message, header *type
 	return &VMEnv{
 		chain:  chain,
 		state:  state,
-		header: header,
+		header: header.Raw(),
 		msg:    msg,
 		typ:    vm.StdVmTy,
 	}
diff --git a/eth/backend.go b/eth/backend.go
index 7bafcbc83e..d911ae6438 100644
--- a/eth/backend.go
+++ b/eth/backend.go
@@ -315,7 +315,7 @@ func New(config *Config) (*Ethereum, error) {
 	// This is for testing only.
 	if config.GenesisBlock != nil {
 		core.WriteBlock(chainDb, config.GenesisBlock)
-		core.WriteHead(chainDb, config.GenesisBlock)
+		core.WriteHeadBlockMeta(chainDb, config.GenesisBlock)
 	}
 
 	if !config.SkipBcVersionCheck {
diff --git a/eth/downloader/downloader.go b/eth/downloader/downloader.go
index 574f2ba15e..a593da0ed2 100644
--- a/eth/downloader/downloader.go
+++ b/eth/downloader/downloader.go
@@ -810,7 +810,7 @@ func (d *Downloader) findAncestor(p *peer) (uint64, error) {
 			finished = true
 			for i := len(headers) - 1; i >= 0; i-- {
 				if d.hasBlock(headers[i].Hash()) {
-					number, hash = headers[i].Number.Uint64(), headers[i].Hash()
+					number, hash = headers[i].Number().Uint64(), headers[i].Hash()
 					break
 				}
 			}
diff --git a/eth/downloader/downloader_test.go b/eth/downloader/downloader_test.go
index 8d009b6717..0eccb1885e 100644
--- a/eth/downloader/downloader_test.go
+++ b/eth/downloader/downloader_test.go
@@ -58,7 +58,11 @@ func makeChain(n int, seed byte, parent *types.Block) ([]common.Hash, map[common
 		}
 		// If the block number is a multiple of 5, add a bonus uncle to the block
 		if i%5 == 0 {
-			block.AddUncle(&types.Header{ParentHash: block.PrevBlock(i - 1).Hash(), Number: big.NewInt(int64(i - 1))})
+			uncle := &types.RawHeader{
+				ParentHash: block.PrevBlock(i - 1).Hash(),
+				Number:     big.NewInt(int64(i - 1)),
+			}
+			block.AddUncle(types.NewHeader(uncle))
 		}
 	})
 	hashes := make([]common.Hash, n+1)
@@ -696,7 +700,7 @@ func testBlockBodyAttackerDropping(t *testing.T, protocol int) {
 		// Assemble a good or bad block, depending of the test
 		raw := core.GenerateChain(genesis, testdb, 1, nil)[0]
 		if tt.failure {
-			parent := types.NewBlock(&types.Header{}, nil, nil, nil)
+			parent := types.NewBlock(new(types.RawHeader), nil, nil, nil)
 			raw = core.GenerateChain(parent, testdb, 1, nil)[0]
 		}
 		block := &Block{OriginPeer: id, RawBlock: raw}
diff --git a/eth/downloader/queue.go b/eth/downloader/queue.go
index 7db78327b3..431dd59f6f 100644
--- a/eth/downloader/queue.go
+++ b/eth/downloader/queue.go
@@ -202,7 +202,7 @@ func (q *queue) Insert(headers []*types.Header) []*types.Header {
 		// Queue the header for body retrieval
 		inserts = append(inserts, header)
 		q.headerPool[hash] = header
-		q.headerQueue.Push(header, -float32(header.Number.Uint64()))
+		q.headerQueue.Push(header, -float32(header.Number().Uint64()))
 	}
 	return inserts
 }
@@ -340,7 +340,7 @@ func (q *queue) Reserve(p *peer, count int) (*fetchRequest, bool, error) {
 		header := q.headerQueue.PopItem().(*types.Header)
 
 		// If the header defines an empty block, deliver straight
-		if header.TxHash == types.DeriveSha(types.Transactions{}) && header.UncleHash == types.CalcUncleHash([]*types.Header{}) {
+		if header.TxHash() == types.DeriveSha(types.Transactions{}) && header.UncleHash() == types.CalcUncleHash([]*types.Header{}) {
 			if err := q.enqueue("", types.NewBlockWithHeader(header)); err != nil {
 				return nil, false, errInvalidChain
 			}
@@ -357,7 +357,7 @@ func (q *queue) Reserve(p *peer, count int) (*fetchRequest, bool, error) {
 	}
 	// Merge all the skipped headers back
 	for _, header := range skip {
-		q.headerQueue.Push(header, -float32(header.Number.Uint64()))
+		q.headerQueue.Push(header, -float32(header.Number().Uint64()))
 	}
 	// Assemble and return the block download request
 	if len(send) == 0 {
@@ -382,7 +382,7 @@ func (q *queue) Cancel(request *fetchRequest) {
 		q.hashQueue.Push(hash, float32(index))
 	}
 	for _, header := range request.Headers {
-		q.headerQueue.Push(header, -float32(header.Number.Uint64()))
+		q.headerQueue.Push(header, -float32(header.Number().Uint64()))
 	}
 	delete(q.pendPool, request.Peer.id)
 }
@@ -408,7 +408,7 @@ func (q *queue) Expire(timeout time.Duration) []string {
 				q.hashQueue.Push(hash, float32(index))
 			}
 			for _, header := range request.Headers {
-				q.headerQueue.Push(header, -float32(header.Number.Uint64()))
+				q.headerQueue.Push(header, -float32(header.Number().Uint64()))
 			}
 			peers = append(peers, id)
 		}
@@ -496,7 +496,7 @@ func (q *queue) Deliver(id string, txLists [][]*types.Transaction, uncleLists []
 			break
 		}
 		// Reconstruct the next block if contents match up
-		if types.DeriveSha(types.Transactions(txLists[i])) != header.TxHash || types.CalcUncleHash(uncleLists[i]) != header.UncleHash {
+		if types.DeriveSha(types.Transactions(txLists[i])) != header.TxHash() || types.CalcUncleHash(uncleLists[i]) != header.UncleHash() {
 			errs = []error{errInvalidBody}
 			break
 		}
@@ -513,7 +513,7 @@ func (q *queue) Deliver(id string, txLists [][]*types.Transaction, uncleLists []
 	// Return all failed or missing fetches to the queue
 	for _, header := range request.Headers {
 		if header != nil {
-			q.headerQueue.Push(header, -float32(header.Number.Uint64()))
+			q.headerQueue.Push(header, -float32(header.Number().Uint64()))
 		}
 	}
 	// If none of the blocks were good, it's a stale delivery
diff --git a/eth/fetcher/fetcher.go b/eth/fetcher/fetcher.go
index b8ec1fc554..9d1c8a038e 100644
--- a/eth/fetcher/fetcher.go
+++ b/eth/fetcher/fetcher.go
@@ -537,8 +537,8 @@ func (f *Fetcher) loop() {
 				// Filter fetcher-requested headers from other synchronisation algorithms
 				if announce := f.fetching[hash]; announce != nil && f.fetched[hash] == nil && f.completing[hash] == nil && f.queued[hash] == nil {
 					// If the delivered header does not match the promised number, drop the announcer
-					if header.Number.Uint64() != announce.number {
-						glog.V(logger.Detail).Infof("[eth/62] Peer %s: invalid block number for [%x…]: announced %d, provided %d", announce.origin, header.Hash().Bytes()[:4], announce.number, header.Number.Uint64())
+					if header.Number().Uint64() != announce.number {
+						glog.V(logger.Detail).Infof("[eth/62] Peer %s: invalid block number for [%x…]: announced %d, provided %d", announce.origin, header.Hash().Bytes()[:4], announce.number, header.Number().Uint64())
 						f.dropPeer(announce.origin)
 						f.forgetHash(hash)
 						continue
@@ -549,8 +549,8 @@ func (f *Fetcher) loop() {
 						announce.time = task.time
 
 						// If the block is empty (header only), short circuit into the final import queue
-						if header.TxHash == types.DeriveSha(types.Transactions{}) && header.UncleHash == types.CalcUncleHash([]*types.Header{}) {
-							glog.V(logger.Detail).Infof("[eth/62] Peer %s: block #%d [%x…] empty, skipping body retrieval", announce.origin, header.Number.Uint64(), header.Hash().Bytes()[:4])
+						if header.TxHash() == types.DeriveSha(types.Transactions{}) && header.UncleHash() == types.CalcUncleHash([]*types.Header{}) {
+							glog.V(logger.Detail).Infof("[eth/62] Peer %s: block #%d [%x…] empty, skipping body retrieval", announce.origin, header.Number().Uint64(), header.Hash().Bytes()[:4])
 
 							block := types.NewBlockWithHeader(header)
 							block.ReceivedAt = task.time
@@ -562,7 +562,7 @@ func (f *Fetcher) loop() {
 						// Otherwise add to the list of blocks needing completion
 						incomplete = append(incomplete, announce)
 					} else {
-						glog.V(logger.Detail).Infof("[eth/62] Peer %s: block #%d [%x…] already imported, discarding header", announce.origin, header.Number.Uint64(), header.Hash().Bytes()[:4])
+						glog.V(logger.Detail).Infof("[eth/62] Peer %s: block #%d [%x…] already imported, discarding header", announce.origin, header.Number().Uint64(), header.Hash().Bytes()[:4])
 						f.forgetHash(hash)
 					}
 				} else {
@@ -614,7 +614,7 @@ func (f *Fetcher) loop() {
 						txnHash := types.DeriveSha(types.Transactions(task.transactions[i]))
 						uncleHash := types.CalcUncleHash(task.uncles[i])
 
-						if txnHash == announce.header.TxHash && uncleHash == announce.header.UncleHash {
+						if txnHash == announce.header.TxHash() && uncleHash == announce.header.UncleHash() {
 							// Mark the body matched, reassemble if still unknown
 							matched = true
 
diff --git a/eth/fetcher/fetcher_test.go b/eth/fetcher/fetcher_test.go
index 707d8d7583..fafd171750 100644
--- a/eth/fetcher/fetcher_test.go
+++ b/eth/fetcher/fetcher_test.go
@@ -37,7 +37,7 @@ var (
 	testKey, _   = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 	testAddress  = crypto.PubkeyToAddress(testKey.PublicKey)
 	genesis      = core.GenesisBlockForTesting(testdb, testAddress, big.NewInt(1000000000))
-	unknownBlock = types.NewBlock(&types.Header{GasLimit: params.GenesisGasLimit}, nil, nil, nil)
+	unknownBlock = types.NewBlock(&types.RawHeader{GasLimit: params.GenesisGasLimit}, nil, nil, nil)
 )
 
 // makeChain creates a chain of n blocks starting at and including parent.
@@ -58,7 +58,11 @@ func makeChain(n int, seed byte, parent *types.Block) ([]common.Hash, map[common
 		}
 		// If the block number is a multiple of 5, add a bonus uncle to the block
 		if i%5 == 0 {
-			block.AddUncle(&types.Header{ParentHash: block.PrevBlock(i - 1).Hash(), Number: big.NewInt(int64(i - 1))})
+			uncle := &types.RawHeader{
+				ParentHash: block.PrevBlock(i - 1).Hash(),
+				Number:     big.NewInt(int64(i - 1)),
+			}
+			block.AddUncle(types.NewHeader(uncle))
 		}
 	})
 	hashes := make([]common.Hash, n+1)
diff --git a/eth/handler.go b/eth/handler.go
index 95f4e8ce21..8e862d9245 100644
--- a/eth/handler.go
+++ b/eth/handler.go
@@ -371,7 +371,7 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 				// Hash based traversal towards the genesis block
 				for i := 0; i < int(query.Skip)+1; i++ {
 					if header := pm.chainman.GetHeader(query.Origin.Hash); header != nil {
-						query.Origin.Hash = header.ParentHash
+						query.Origin.Hash = header.ParentHash()
 					} else {
 						unknown = true
 						break
@@ -379,7 +379,7 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 				}
 			case query.Origin.Hash != (common.Hash{}) && !query.Reverse:
 				// Hash based traversal towards the leaf block
-				if header := pm.chainman.GetHeaderByNumber(origin.Number.Uint64() + query.Skip + 1); header != nil {
+				if header := pm.chainman.GetHeaderByNumber(origin.Number().Uint64() + query.Skip + 1); header != nil {
 					if pm.chainman.GetBlockHashesFromHash(header.Hash(), query.Skip+1)[query.Skip] == query.Origin.Hash {
 						query.Origin.Hash = header.Hash()
 					} else {
diff --git a/eth/handler_test.go b/eth/handler_test.go
index 6400d4e789..64dc239523 100644
--- a/eth/handler_test.go
+++ b/eth/handler_test.go
@@ -401,12 +401,12 @@ func testGetNodeData(t *testing.T, protocol int) {
 			block.SetExtra([]byte("yeehaw"))
 		case 3:
 			// Block 4 includes blocks 2 and 3 as uncle headers (with modified extra data).
-			b2 := block.PrevBlock(1).Header()
+			b2 := block.PrevBlock(1).Header().Raw()
 			b2.Extra = []byte("foo")
-			block.AddUncle(b2)
-			b3 := block.PrevBlock(2).Header()
+			block.AddUncle(types.NewHeader(b2))
+			b3 := block.PrevBlock(2).Header().Raw()
 			b3.Extra = []byte("foo")
-			block.AddUncle(b3)
+			block.AddUncle(types.NewHeader(b3))
 		}
 	}
 	// Assemble the test environment
@@ -490,12 +490,12 @@ func testGetReceipt(t *testing.T, protocol int) {
 			block.SetExtra([]byte("yeehaw"))
 		case 3:
 			// Block 4 includes blocks 2 and 3 as uncle headers (with modified extra data).
-			b2 := block.PrevBlock(1).Header()
+			b2 := block.PrevBlock(1).Header().Raw()
 			b2.Extra = []byte("foo")
-			block.AddUncle(b2)
-			b3 := block.PrevBlock(2).Header()
+			block.AddUncle(types.NewHeader(b2))
+			b3 := block.PrevBlock(2).Header().Raw()
 			b3.Extra = []byte("foo")
-			block.AddUncle(b3)
+			block.AddUncle(types.NewHeader(b3))
 		}
 	}
 	// Assemble the test environment
diff --git a/miner/worker.go b/miner/worker.go
index 16a16931d7..c593be698c 100644
--- a/miner/worker.go
+++ b/miner/worker.go
@@ -75,7 +75,7 @@ type Work struct {
 
 	Block *types.Block // the new block
 
-	header   *types.Header
+	header   *types.RawHeader
 	txs      []*types.Transaction
 	receipts []*types.Receipt
 
@@ -346,7 +346,7 @@ func (self *worker) push(work *Work) {
 }
 
 // makeCurrent creates a new environment for the current cycle.
-func (self *worker) makeCurrent(parent *types.Block, header *types.Header) {
+func (self *worker) makeCurrent(parent *types.Block, header *types.RawHeader) {
 	state := state.New(parent.Root(), self.eth.ChainDb())
 	work := &Work{
 		state:     state,
@@ -443,9 +443,9 @@ func (self *worker) commitNewWork() {
 		glog.V(logger.Info).Infoln("We are too far in the future. Waiting for", wait)
 		time.Sleep(wait)
 	}
-
 	num := parent.Number()
-	header := &types.Header{
+
+	header := &types.RawHeader{
 		ParentHash: parent.Hash(),
 		Number:     num.Add(num, common.Big1),
 		Difficulty: core.CalcDifficulty(uint64(tstamp), parent.Time().Uint64(), parent.Number(), parent.Difficulty()),
@@ -455,7 +455,6 @@ func (self *worker) commitNewWork() {
 		Extra:      self.extra,
 		Time:       big.NewInt(tstamp),
 	}
-
 	previous := self.current
 	self.makeCurrent(parent, header)
 	work := self.current
@@ -526,7 +525,7 @@ func (self *worker) commitNewWork() {
 
 	if atomic.LoadInt32(&self.mining) == 1 {
 		// commit state root after all state transitions.
-		core.AccumulateRewards(work.state, header, uncles)
+		core.AccumulateRewards(work.state, types.NewHeader(header), uncles)
 		work.state.SyncObjects()
 		header.Root = work.state.Root()
 	}
@@ -549,8 +548,8 @@ func (self *worker) commitUncle(work *Work, uncle *types.Header) error {
 	if work.uncles.Has(hash) {
 		return core.UncleError("Uncle not unique")
 	}
-	if !work.ancestors.Has(uncle.ParentHash) {
-		return core.UncleError(fmt.Sprintf("Uncle's parent unknown (%x)", uncle.ParentHash[0:4]))
+	if parent := uncle.ParentHash(); !work.ancestors.Has(parent) {
+		return core.UncleError(fmt.Sprintf("Uncle's parent unknown (%x)", parent[:4]))
 	}
 	if work.family.Has(hash) {
 		return core.UncleError(fmt.Sprintf("Uncle already in family (%x)", hash))
@@ -619,7 +618,7 @@ func (env *Work) commitTransactions(transactions types.Transactions, gasPrice *b
 
 func (env *Work) commitTransaction(tx *types.Transaction, proc *core.BlockProcessor) error {
 	snap := env.state.Copy()
-	receipt, _, err := proc.ApplyTransaction(env.coinbase, env.state, env.header, tx, env.header.GasUsed, true)
+	receipt, _, err := proc.ApplyTransaction(env.coinbase, env.state, types.NewHeader(env.header), tx, env.header.GasUsed, true)
 	if err != nil {
 		env.state.Set(snap)
 		return err
diff --git a/rpc/api/parsing.go b/rpc/api/parsing.go
index 5858bc1361..f700862bbc 100644
--- a/rpc/api/parsing.go
+++ b/rpc/api/parsing.go
@@ -383,21 +383,21 @@ func NewUncleRes(h *types.Header) *UncleRes {
 	}
 
 	var v = new(UncleRes)
-	v.BlockNumber = newHexNum(h.Number)
+	v.BlockNumber = newHexNum(h.Number())
 	v.BlockHash = newHexData(h.Hash())
-	v.ParentHash = newHexData(h.ParentHash)
-	v.Sha3Uncles = newHexData(h.UncleHash)
-	v.Nonce = newHexData(h.Nonce[:])
-	v.LogsBloom = newHexData(h.Bloom)
-	v.TransactionRoot = newHexData(h.TxHash)
-	v.StateRoot = newHexData(h.Root)
-	v.Miner = newHexData(h.Coinbase)
-	v.Difficulty = newHexNum(h.Difficulty)
-	v.ExtraData = newHexData(h.Extra)
-	v.GasLimit = newHexNum(h.GasLimit)
-	v.GasUsed = newHexNum(h.GasUsed)
-	v.UnixTimestamp = newHexNum(h.Time)
-	v.ReceiptHash = newHexData(h.ReceiptHash)
+	v.ParentHash = newHexData(h.ParentHash())
+	v.Sha3Uncles = newHexData(h.UncleHash())
+	v.Nonce = newHexData(h.Nonce())
+	v.LogsBloom = newHexData(h.Bloom())
+	v.TransactionRoot = newHexData(h.TxHash())
+	v.StateRoot = newHexData(h.Root())
+	v.Miner = newHexData(h.Coinbase())
+	v.Difficulty = newHexNum(h.Difficulty())
+	v.ExtraData = newHexData(h.Extra())
+	v.GasLimit = newHexNum(h.GasLimit())
+	v.GasUsed = newHexNum(h.GasUsed())
+	v.UnixTimestamp = newHexNum(h.Time())
+	v.ReceiptHash = newHexData(h.ReceiptHash())
 
 	return v
 }
diff --git a/tests/block_test_util.go b/tests/block_test_util.go
index 2090afce71..764f550f1b 100644
--- a/tests/block_test_util.go
+++ b/tests/block_test_util.go
@@ -297,77 +297,77 @@ func (t *BlockTest) TryBlocksInsert(chainManager *core.ChainManager) error {
 
 func (s *BlockTest) validateBlockHeader(h *btHeader, h2 *types.Header) error {
 	expectedBloom := mustConvertBytes(h.Bloom)
-	if !bytes.Equal(expectedBloom, h2.Bloom.Bytes()) {
-		return fmt.Errorf("Bloom: expected: %v, decoded: %v", expectedBloom, h2.Bloom.Bytes())
+	if !bytes.Equal(expectedBloom, h2.Bloom().Bytes()) {
+		return fmt.Errorf("Bloom: expected: %v, decoded: %v", expectedBloom, h2.Bloom().Bytes())
 	}
 
 	expectedCoinbase := mustConvertBytes(h.Coinbase)
-	if !bytes.Equal(expectedCoinbase, h2.Coinbase.Bytes()) {
-		return fmt.Errorf("Coinbase: expected: %v, decoded: %v", expectedCoinbase, h2.Coinbase.Bytes())
+	if !bytes.Equal(expectedCoinbase, h2.Coinbase().Bytes()) {
+		return fmt.Errorf("Coinbase: expected: %v, decoded: %v", expectedCoinbase, h2.Coinbase().Bytes())
 	}
 
 	expectedMixHashBytes := mustConvertBytes(h.MixHash)
-	if !bytes.Equal(expectedMixHashBytes, h2.MixDigest.Bytes()) {
-		return fmt.Errorf("MixHash: expected: %v, decoded: %v", expectedMixHashBytes, h2.MixDigest.Bytes())
+	if !bytes.Equal(expectedMixHashBytes, h2.MixDigest().Bytes()) {
+		return fmt.Errorf("MixHash: expected: %v, decoded: %v", expectedMixHashBytes, h2.MixDigest().Bytes())
 	}
 
 	expectedNonce := mustConvertBytes(h.Nonce)
-	if !bytes.Equal(expectedNonce, h2.Nonce[:]) {
-		return fmt.Errorf("Nonce: expected: %v, decoded: %v", expectedNonce, h2.Nonce)
+	if nonce := h2.Nonce(); !bytes.Equal(expectedNonce, nonce[:]) {
+		return fmt.Errorf("Nonce: expected: %v, decoded: %v", expectedNonce, nonce)
 	}
 
 	expectedNumber := mustConvertBigInt(h.Number, 16)
-	if expectedNumber.Cmp(h2.Number) != 0 {
-		return fmt.Errorf("Number: expected: %v, decoded: %v", expectedNumber, h2.Number)
+	if expectedNumber.Cmp(h2.Number()) != 0 {
+		return fmt.Errorf("Number: expected: %v, decoded: %v", expectedNumber, h2.Number())
 	}
 
 	expectedParentHash := mustConvertBytes(h.ParentHash)
-	if !bytes.Equal(expectedParentHash, h2.ParentHash.Bytes()) {
-		return fmt.Errorf("Parent hash: expected: %v, decoded: %v", expectedParentHash, h2.ParentHash.Bytes())
+	if !bytes.Equal(expectedParentHash, h2.ParentHash().Bytes()) {
+		return fmt.Errorf("Parent hash: expected: %v, decoded: %v", expectedParentHash, h2.ParentHash().Bytes())
 	}
 
 	expectedReceiptHash := mustConvertBytes(h.ReceiptTrie)
-	if !bytes.Equal(expectedReceiptHash, h2.ReceiptHash.Bytes()) {
-		return fmt.Errorf("Receipt hash: expected: %v, decoded: %v", expectedReceiptHash, h2.ReceiptHash.Bytes())
+	if !bytes.Equal(expectedReceiptHash, h2.ReceiptHash().Bytes()) {
+		return fmt.Errorf("Receipt hash: expected: %v, decoded: %v", expectedReceiptHash, h2.ReceiptHash().Bytes())
 	}
 
 	expectedTxHash := mustConvertBytes(h.TransactionsTrie)
-	if !bytes.Equal(expectedTxHash, h2.TxHash.Bytes()) {
-		return fmt.Errorf("Tx hash: expected: %v, decoded: %v", expectedTxHash, h2.TxHash.Bytes())
+	if !bytes.Equal(expectedTxHash, h2.TxHash().Bytes()) {
+		return fmt.Errorf("Tx hash: expected: %v, decoded: %v", expectedTxHash, h2.TxHash().Bytes())
 	}
 
 	expectedStateHash := mustConvertBytes(h.StateRoot)
-	if !bytes.Equal(expectedStateHash, h2.Root.Bytes()) {
-		return fmt.Errorf("State hash: expected: %v, decoded: %v", expectedStateHash, h2.Root.Bytes())
+	if !bytes.Equal(expectedStateHash, h2.Root().Bytes()) {
+		return fmt.Errorf("State hash: expected: %v, decoded: %v", expectedStateHash, h2.Root().Bytes())
 	}
 
 	expectedUncleHash := mustConvertBytes(h.UncleHash)
-	if !bytes.Equal(expectedUncleHash, h2.UncleHash.Bytes()) {
-		return fmt.Errorf("Uncle hash: expected: %v, decoded: %v", expectedUncleHash, h2.UncleHash.Bytes())
+	if !bytes.Equal(expectedUncleHash, h2.UncleHash().Bytes()) {
+		return fmt.Errorf("Uncle hash: expected: %v, decoded: %v", expectedUncleHash, h2.UncleHash().Bytes())
 	}
 
 	expectedExtraData := mustConvertBytes(h.ExtraData)
-	if !bytes.Equal(expectedExtraData, h2.Extra) {
-		return fmt.Errorf("Extra data: expected: %v, decoded: %v", expectedExtraData, h2.Extra)
+	if !bytes.Equal(expectedExtraData, h2.Extra()) {
+		return fmt.Errorf("Extra data: expected: %v, decoded: %v", expectedExtraData, h2.Extra())
 	}
 
 	expectedDifficulty := mustConvertBigInt(h.Difficulty, 16)
-	if expectedDifficulty.Cmp(h2.Difficulty) != 0 {
-		return fmt.Errorf("Difficulty: expected: %v, decoded: %v", expectedDifficulty, h2.Difficulty)
+	if expectedDifficulty.Cmp(h2.Difficulty()) != 0 {
+		return fmt.Errorf("Difficulty: expected: %v, decoded: %v", expectedDifficulty, h2.Difficulty())
 	}
 
 	expectedGasLimit := mustConvertBigInt(h.GasLimit, 16)
-	if expectedGasLimit.Cmp(h2.GasLimit) != 0 {
-		return fmt.Errorf("GasLimit: expected: %v, decoded: %v", expectedGasLimit, h2.GasLimit)
+	if expectedGasLimit.Cmp(h2.GasLimit()) != 0 {
+		return fmt.Errorf("GasLimit: expected: %v, decoded: %v", expectedGasLimit, h2.GasLimit())
 	}
 	expectedGasUsed := mustConvertBigInt(h.GasUsed, 16)
-	if expectedGasUsed.Cmp(h2.GasUsed) != 0 {
-		return fmt.Errorf("GasUsed: expected: %v, decoded: %v", expectedGasUsed, h2.GasUsed)
+	if expectedGasUsed.Cmp(h2.GasUsed()) != 0 {
+		return fmt.Errorf("GasUsed: expected: %v, decoded: %v", expectedGasUsed, h2.GasUsed())
 	}
 
 	expectedTimestamp := mustConvertBigInt(h.Timestamp, 16)
-	if expectedTimestamp.Cmp(h2.Time) != 0 {
-		return fmt.Errorf("Timestamp: expected: %v, decoded: %v", expectedTimestamp, h2.Time)
+	if expectedTimestamp.Cmp(h2.Time()) != 0 {
+		return fmt.Errorf("Timestamp: expected: %v, decoded: %v", expectedTimestamp, h2.Time())
 	}
 
 	return nil
@@ -440,14 +440,14 @@ func convertBlockTest(in *btJSON) (out *BlockTest, err error) {
 func mustConvertGenesis(testGenesis btHeader) *types.Block {
 	hdr := mustConvertHeader(testGenesis)
 	hdr.Number = big.NewInt(0)
-	b := types.NewBlockWithHeader(hdr)
+	b := types.NewBlockWithRawHeader(hdr)
 	b.Td = new(big.Int)
 	return b
 }
 
-func mustConvertHeader(in btHeader) *types.Header {
+func mustConvertHeader(in btHeader) *types.RawHeader {
 	// hex decode these fields
-	header := &types.Header{
+	return &types.RawHeader{
 		//SeedHash:    mustConvertBytes(in.SeedHash),
 		MixDigest:   mustConvertHash(in.MixHash),
 		Bloom:       mustConvertBloom(in.Bloom),
@@ -464,7 +464,6 @@ func mustConvertHeader(in btHeader) *types.Header {
 		Time:        mustConvertBigInt(in.Timestamp, 16),
 		Nonce:       types.EncodeNonce(mustConvertUint(in.Nonce, 16)),
 	}
-	return header
 }
 
 func mustConvertBlock(testBlock btBlock) (*types.Block, error) {