diff --git a/Dockerfile b/Dockerfile
index b7e23aaab..966614e71 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -26,12 +26,11 @@ RUN tar -C /usr/local -xzf go*.tar.gz && go version
 ADD https://api.github.com/repos/ethereum/go-ethereum/git/refs/heads/develop file_does_not_exist
 
 ## Fetch and install go-ethereum
-RUN go get github.com/tools/godep
-RUN go get -d github.com/ethereum/go-ethereum/...
+RUN mkdir -p $GOPATH/src/github.com/ethereum/
+RUN git clone https://github.com/ethereum/go-ethereum $GOPATH/src/github.com/ethereum/go-ethereum
 WORKDIR $GOPATH/src/github.com/ethereum/go-ethereum
 RUN git checkout develop
-RUN godep restore
-RUN go install -v ./cmd/ethereum
+RUN GOPATH=$GOPATH:$GOPATH/src/github.com/ethereum/go-ethereum/Godeps/_workspace go install -v ./cmd/ethereum
 
 ## Run & expose JSON RPC
 ENTRYPOINT ["ethereum", "-rpc=true", "-rpcport=8545"]
diff --git a/cmd/ethereum/main.go b/cmd/ethereum/main.go
index 459059e6c..9ebbd9880 100644
--- a/cmd/ethereum/main.go
+++ b/cmd/ethereum/main.go
@@ -30,6 +30,7 @@ import (
 	"time"
 
 	"github.com/codegangsta/cli"
+	"github.com/ethereum/ethash"
 	"github.com/ethereum/go-ethereum/cmd/utils"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
@@ -54,6 +55,17 @@ func init() {
 	app.HideVersion = true // we have a command to print the version
 	app.Commands = []cli.Command{
 		blocktestCmd,
+		{
+			Action: makedag,
+			Name:   "makedag",
+			Usage:  "generate ethash dag (for testing)",
+			Description: `
+The makedag command generates an ethash DAG in /tmp/dag.
+
+This command exists to support the system testing project.
+Regular users do not need to execute it.
+`,
+		},
 		{
 			Action: version,
 			Name:   "version",
@@ -318,6 +330,15 @@ func dump(ctx *cli.Context) {
 	}
 }
 
+func makedag(ctx *cli.Context) {
+	chain, _, _ := utils.GetChain(ctx)
+	pow := ethash.New(chain)
+	fmt.Println("making cache")
+	pow.UpdateCache(true)
+	fmt.Println("making DAG")
+	pow.UpdateDAG()
+}
+
 func version(c *cli.Context) {
 	fmt.Printf(`%v
 Version: %v
diff --git a/common/common.go b/common/common.go
index 1371d18d4..155bb5c2a 100644
--- a/common/common.go
+++ b/common/common.go
@@ -65,6 +65,15 @@ func DefaultDataDir() string {
 	}
 }
 
+func ToHex(b []byte) string {
+	hex := Bytes2Hex(b)
+	// Prefer output of "0x0" instead of "0x"
+	if len(hex) == 0 {
+		hex = "0"
+	}
+	return "0x" + hex
+}
+
 func FromHex(s string) []byte {
 	if len(s) > 1 {
 		if s[0:2] == "0x" {
diff --git a/rpc/api.go b/rpc/api.go
index 3c46684d1..486eec008 100644
--- a/rpc/api.go
+++ b/rpc/api.go
@@ -251,7 +251,7 @@ func (p *EthereumApi) Transact(args *NewTxArgs, reply *interface{}) (err error)
 
 			result, _ := account.Transact(common.FromHex(args.To), common.FromHex(args.Value), common.FromHex(args.Gas), common.FromHex(args.GasPrice), common.FromHex(args.Data))
 			if len(result) > 0 {
-				*reply = toHex(result)
+				*reply = common.ToHex(result)
 			}
 		} else if _, exists := p.register[args.From]; exists {
 			p.register[ags.From] = append(p.register[args.From], args)
@@ -291,7 +291,7 @@ func (p *EthereumApi) GetBalance(args *GetBalanceArgs, reply *interface{}) error
 		return err
 	}
 	state := p.getStateWithNum(args.BlockNumber).SafeGet(args.Address)
-	*reply = toHex(state.Balance().Bytes())
+	*reply = common.ToHex(state.Balance().Bytes())
 	return nil
 }
 
@@ -389,7 +389,7 @@ func (p *EthereumApi) NewWhisperFilter(args *WhisperFilterArgs, reply *interface
 	}
 	id = p.xeth().Whisper().Watch(opts)
 	p.messages[id] = &whisperFilter{timeout: time.Now()}
-	*reply = toHex(big.NewInt(int64(id)).Bytes())
+	*reply = common.ToHex(big.NewInt(int64(id)).Bytes())
 	return nil
 }
 
@@ -485,7 +485,7 @@ func (p *EthereumApi) GetRequestReply(req *RpcRequest, reply *interface{}) error
 		if err := json.Unmarshal(req.Params, &args); err != nil {
 			return err
 		}
-		*reply = toHex(crypto.Sha3(common.FromHex(args.Data)))
+		*reply = common.ToHex(crypto.Sha3(common.FromHex(args.Data)))
 	case "web3_clientVersion":
 		*reply = p.xeth().Backend().Version()
 	case "net_version":
@@ -493,7 +493,7 @@ func (p *EthereumApi) GetRequestReply(req *RpcRequest, reply *interface{}) error
 	case "net_listening":
 		*reply = p.xeth().IsListening()
 	case "net_peerCount":
-		*reply = toHex(big.NewInt(int64(p.xeth().PeerCount())).Bytes())
+		*reply = common.ToHex(big.NewInt(int64(p.xeth().PeerCount())).Bytes())
 	case "eth_coinbase":
 		// TODO handling of empty coinbase due to lack of accounts
 		res := p.xeth().Coinbase()
@@ -505,11 +505,11 @@ func (p *EthereumApi) GetRequestReply(req *RpcRequest, reply *interface{}) error
 	case "eth_mining":
 		*reply = p.xeth().IsMining()
 	case "eth_gasPrice":
-		*reply = toHex(defaultGasPrice.Bytes())
+		*reply = common.ToHex(defaultGasPrice.Bytes())
 	case "eth_accounts":
 		*reply = p.xeth().Accounts()
 	case "eth_blockNumber":
-		*reply = toHex(p.xeth().Backend().ChainManager().CurrentBlock().Number().Bytes())
+		*reply = common.ToHex(p.xeth().Backend().ChainManager().CurrentBlock().Number().Bytes())
 	case "eth_getBalance":
 		args := new(GetBalanceArgs)
 		if err := json.Unmarshal(req.Params, &args); err != nil {
@@ -544,7 +544,7 @@ func (p *EthereumApi) GetRequestReply(req *RpcRequest, reply *interface{}) error
 		if err != nil {
 			return err
 		}
-		*reply = toHex(big.NewInt(v).Bytes())
+		*reply = common.ToHex(big.NewInt(v).Bytes())
 	case "eth_getBlockTransactionCountByNumber":
 		args := new(GetBlockByNumberArgs)
 		if err := json.Unmarshal(req.Params, &args); err != nil {
@@ -555,7 +555,7 @@ func (p *EthereumApi) GetRequestReply(req *RpcRequest, reply *interface{}) error
 		if err != nil {
 			return err
 		}
-		*reply = toHex(big.NewInt(v).Bytes())
+		*reply = common.ToHex(big.NewInt(v).Bytes())
 	case "eth_getUncleCountByBlockHash":
 		args := new(GetBlockByHashArgs)
 		if err := json.Unmarshal(req.Params, &args); err != nil {
@@ -566,7 +566,7 @@ func (p *EthereumApi) GetRequestReply(req *RpcRequest, reply *interface{}) error
 		if err != nil {
 			return err
 		}
-		*reply = toHex(big.NewInt(v).Bytes())
+		*reply = common.ToHex(big.NewInt(v).Bytes())
 	case "eth_getUncleCountByBlockNumber":
 		args := new(GetBlockByNumberArgs)
 		if err := json.Unmarshal(req.Params, &args); err != nil {
@@ -577,7 +577,7 @@ func (p *EthereumApi) GetRequestReply(req *RpcRequest, reply *interface{}) error
 		if err != nil {
 			return err
 		}
-		*reply = toHex(big.NewInt(v).Bytes())
+		*reply = common.ToHex(big.NewInt(v).Bytes())
 	case "eth_getData", "eth_getCode":
 		args := new(GetDataArgs)
 		if err := json.Unmarshal(req.Params, &args); err != nil {
diff --git a/rpc/responses.go b/rpc/responses.go
index 5b2b9d488..5e197b729 100644
--- a/rpc/responses.go
+++ b/rpc/responses.go
@@ -57,23 +57,23 @@ func (b *BlockRes) MarshalJSON() ([]byte, error) {
 	}
 
 	// convert strict types to hexified strings
-	ext.BlockNumber = toHex(big.NewInt(b.BlockNumber).Bytes())
+	ext.BlockNumber = common.ToHex(big.NewInt(b.BlockNumber).Bytes())
 	ext.BlockHash = b.BlockHash.Hex()
 	ext.ParentHash = b.ParentHash.Hex()
-	ext.Nonce = toHex(b.Nonce[:])
+	ext.Nonce = common.ToHex(b.Nonce[:])
 	ext.Sha3Uncles = b.Sha3Uncles.Hex()
-	ext.LogsBloom = toHex(b.LogsBloom[:])
+	ext.LogsBloom = common.ToHex(b.LogsBloom[:])
 	ext.TransactionRoot = b.TransactionRoot.Hex()
 	ext.StateRoot = b.StateRoot.Hex()
 	ext.Miner = b.Miner.Hex()
-	ext.Difficulty = toHex(big.NewInt(b.Difficulty).Bytes())
-	ext.TotalDifficulty = toHex(big.NewInt(b.TotalDifficulty).Bytes())
-	ext.Size = toHex(big.NewInt(b.Size).Bytes())
-	// ext.ExtraData = toHex(b.ExtraData)
-	ext.GasLimit = toHex(big.NewInt(b.GasLimit).Bytes())
-	// ext.MinGasPrice = toHex(big.NewInt(b.MinGasPrice).Bytes())
-	ext.GasUsed = toHex(big.NewInt(b.GasUsed).Bytes())
-	ext.UnixTimestamp = toHex(big.NewInt(b.UnixTimestamp).Bytes())
+	ext.Difficulty = common.ToHex(big.NewInt(b.Difficulty).Bytes())
+	ext.TotalDifficulty = common.ToHex(big.NewInt(b.TotalDifficulty).Bytes())
+	ext.Size = common.ToHex(big.NewInt(b.Size).Bytes())
+	// ext.ExtraData = common.ToHex(b.ExtraData)
+	ext.GasLimit = common.ToHex(big.NewInt(b.GasLimit).Bytes())
+	// ext.MinGasPrice = common.ToHex(big.NewInt(b.MinGasPrice).Bytes())
+	ext.GasUsed = common.ToHex(big.NewInt(b.GasUsed).Bytes())
+	ext.UnixTimestamp = common.ToHex(big.NewInt(b.UnixTimestamp).Bytes())
 	ext.Transactions = make([]interface{}, len(b.Transactions))
 	if b.fullTx {
 		for i, tx := range b.Transactions {
@@ -162,20 +162,20 @@ func (t *TransactionRes) MarshalJSON() ([]byte, error) {
 	}
 
 	ext.Hash = t.Hash.Hex()
-	ext.Nonce = toHex(big.NewInt(t.Nonce).Bytes())
+	ext.Nonce = common.ToHex(big.NewInt(t.Nonce).Bytes())
 	ext.BlockHash = t.BlockHash.Hex()
-	ext.BlockNumber = toHex(big.NewInt(t.BlockNumber).Bytes())
-	ext.TxIndex = toHex(big.NewInt(t.TxIndex).Bytes())
+	ext.BlockNumber = common.ToHex(big.NewInt(t.BlockNumber).Bytes())
+	ext.TxIndex = common.ToHex(big.NewInt(t.TxIndex).Bytes())
 	ext.From = t.From.Hex()
 	if t.To == nil {
 		ext.To = "0x00"
 	} else {
 		ext.To = t.To.Hex()
 	}
-	ext.Value = toHex(big.NewInt(t.Value).Bytes())
-	ext.Gas = toHex(big.NewInt(t.Gas).Bytes())
-	ext.GasPrice = toHex(big.NewInt(t.GasPrice).Bytes())
-	ext.Input = toHex(t.Input)
+	ext.Value = common.ToHex(big.NewInt(t.Value).Bytes())
+	ext.Gas = common.ToHex(big.NewInt(t.Gas).Bytes())
+	ext.GasPrice = common.ToHex(big.NewInt(t.GasPrice).Bytes())
+	ext.Input = common.ToHex(t.Input)
 
 	return json.Marshal(ext)
 }
diff --git a/rpc/util.go b/rpc/util.go
index b9b0fa442..d3c3420ae 100644
--- a/rpc/util.go
+++ b/rpc/util.go
@@ -124,17 +124,8 @@ func (self JsonWrapper) ParseRequestBody(req *http.Request) (RpcRequest, error)
 	return reqParsed, nil
 }
 
-func toHex(b []byte) string {
-	hex := common.Bytes2Hex(b)
-	// Prefer output of "0x0" instead of "0x"
-	if len(hex) == 0 {
-		hex = "0"
-	}
-	return "0x" + hex
-}
-
 func i2hex(n int) string {
-	return toHex(big.NewInt(int64(n)).Bytes())
+	return common.ToHex(big.NewInt(int64(n)).Bytes())
 }
 
 type RpcServer interface {
@@ -156,7 +147,7 @@ func toLogs(logs state.Logs) (ls []Log) {
 		var l Log
 		l.Topic = make([]string, len(log.Topics()))
 		l.Address = log.Address().Hex()
-		l.Data = toHex(log.Data())
+		l.Data = common.ToHex(log.Data())
 		l.Number = log.Number()
 		for j, topic := range log.Topics() {
 			l.Topic[j] = topic.Hex()
diff --git a/ui/qt/qwhisper/whisper.go b/ui/qt/qwhisper/whisper.go
index 90ec822aa..bf165bbcc 100644
--- a/ui/qt/qwhisper/whisper.go
+++ b/ui/qt/qwhisper/whisper.go
@@ -4,8 +4,8 @@ package qwhisper
 import (
 	"time"
 
-	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/whisper"
 	"github.com/obscuren/qml"
@@ -13,8 +13,6 @@ import (
 
 var qlogger = logger.NewLogger("QSHH")
 
-func toHex(b []byte) string { return "0x" + common.Bytes2Hex(b) }
-
 type Whisper struct {
 	*whisper.Whisper
 	view qml.Object
@@ -66,7 +64,7 @@ func (self *Whisper) Post(payload []string, to, from string, topics []string, pr
 func (self *Whisper) NewIdentity() string {
 	key := self.Whisper.NewIdentity()
 
-	return toHex(crypto.FromECDSAPub(&key.PublicKey))
+	return common.ToHex(crypto.FromECDSAPub(&key.PublicKey))
 }
 
 func (self *Whisper) HasIdentity(key string) bool {
diff --git a/xeth/types.go b/xeth/types.go
index d8d6ff19f..b4ba7bab0 100644
--- a/xeth/types.go
+++ b/xeth/types.go
@@ -14,10 +14,6 @@ import (
 	"github.com/ethereum/go-ethereum/state"
 )
 
-func toHex(b []byte) string {
-	return "0x" + common.Bytes2Hex(b)
-}
-
 type Object struct {
 	*state.StateObject
 }
@@ -49,7 +45,7 @@ func (self *Object) Storage() (storage map[string]string) {
 	for it.Next() {
 		var data []byte
 		rlp.Decode(bytes.NewReader(it.Value), &data)
-		storage[toHex(it.Key)] = toHex(data)
+		storage[common.ToHex(it.Key)] = common.ToHex(data)
 	}
 
 	return
@@ -95,12 +91,12 @@ func NewBlock(block *types.Block) *Block {
 	return &Block{
 		ref: block, Size: block.Size().String(),
 		Number: int(block.NumberU64()), GasUsed: block.GasUsed().String(),
-		GasLimit: block.GasLimit().String(), Hash: toHex(block.Hash().Bytes()),
+		GasLimit: block.GasLimit().String(), Hash: block.Hash().Hex(),
 		Transactions: txlist, Uncles: ulist,
 		Time:     block.Time(),
-		Coinbase: toHex(block.Coinbase().Bytes()),
-		PrevHash: toHex(block.ParentHash().Bytes()),
-		Bloom:    toHex(block.Bloom().Bytes()),
+		Coinbase: block.Coinbase().Hex(),
+		PrevHash: block.ParentHash().Hex(),
+		Bloom:    common.ToHex(block.Bloom().Bytes()),
 		Raw:      block.String(),
 	}
 }
@@ -151,10 +147,10 @@ func NewTx(tx *types.Transaction) *Transaction {
 	if createsContract {
 		data = strings.Join(core.Disassemble(tx.Data()), "\n")
 	} else {
-		data = toHex(tx.Data())
+		data = common.ToHex(tx.Data())
 	}
 
-	return &Transaction{ref: tx, Hash: hash, Value: common.CurrencyToString(tx.Value()), Address: receiver, Contract: createsContract, Gas: tx.Gas().String(), GasPrice: tx.GasPrice().String(), Data: data, Sender: sender.Hex(), CreatesContract: createsContract, RawData: toHex(tx.Data())}
+	return &Transaction{ref: tx, Hash: hash, Value: common.CurrencyToString(tx.Value()), Address: receiver, Contract: createsContract, Gas: tx.Gas().String(), GasPrice: tx.GasPrice().String(), Data: data, Sender: sender.Hex(), CreatesContract: createsContract, RawData: common.ToHex(tx.Data())}
 }
 
 func (self *Transaction) ToString() string {
@@ -168,7 +164,7 @@ type Key struct {
 }
 
 func NewKey(key *crypto.KeyPair) *Key {
-	return &Key{toHex(key.Address()), toHex(key.PrivateKey), toHex(key.PublicKey)}
+	return &Key{common.ToHex(key.Address()), common.ToHex(key.PrivateKey), common.ToHex(key.PublicKey)}
 }
 
 type PReceipt struct {
@@ -181,9 +177,9 @@ type PReceipt struct {
 func NewPReciept(contractCreation bool, creationAddress, hash, address []byte) *PReceipt {
 	return &PReceipt{
 		contractCreation,
-		toHex(creationAddress),
-		toHex(hash),
-		toHex(address),
+		common.ToHex(creationAddress),
+		common.ToHex(hash),
+		common.ToHex(address),
 	}
 }
 
@@ -220,8 +216,8 @@ type Receipt struct {
 func NewReciept(contractCreation bool, creationAddress, hash, address []byte) *Receipt {
 	return &Receipt{
 		contractCreation,
-		toHex(creationAddress),
-		toHex(hash),
-		toHex(address),
+		common.ToHex(creationAddress),
+		common.ToHex(hash),
+		common.ToHex(address),
 	}
 }
diff --git a/xeth/whisper.go b/xeth/whisper.go
index c0be4c392..72e1ee04f 100644
--- a/xeth/whisper.go
+++ b/xeth/whisper.go
@@ -56,7 +56,7 @@ func (self *Whisper) Post(payload string, to, from string, topics []string, prio
 func (self *Whisper) NewIdentity() string {
 	key := self.Whisper.NewIdentity()
 
-	return toHex(crypto.FromECDSAPub(&key.PublicKey))
+	return common.ToHex(crypto.FromECDSAPub(&key.PublicKey))
 }
 
 func (self *Whisper) HasIdentity(key string) bool {
@@ -112,9 +112,9 @@ type WhisperMessage struct {
 func NewWhisperMessage(msg *whisper.Message) WhisperMessage {
 	return WhisperMessage{
 		ref:     msg,
-		Payload: toHex(msg.Payload),
-		From:    toHex(crypto.FromECDSAPub(msg.Recover())),
-		To:      toHex(crypto.FromECDSAPub(msg.To)),
+		Payload: common.ToHex(msg.Payload),
+		From:    common.ToHex(crypto.FromECDSAPub(msg.Recover())),
+		To:      common.ToHex(crypto.FromECDSAPub(msg.To)),
 		Sent:    msg.Sent,
 	}
 }
diff --git a/xeth/xeth.go b/xeth/xeth.go
index 672b83332..686ed4432 100644
--- a/xeth/xeth.go
+++ b/xeth/xeth.go
@@ -170,7 +170,7 @@ func (self *XEth) Accounts() []string {
 	accounts, _ := self.eth.AccountManager().Accounts()
 	accountAddresses := make([]string, len(accounts))
 	for i, ac := range accounts {
-		accountAddresses[i] = toHex(ac.Address)
+		accountAddresses[i] = common.ToHex(ac.Address)
 	}
 	return accountAddresses
 }
@@ -201,7 +201,7 @@ func (self *XEth) IsListening() bool {
 
 func (self *XEth) Coinbase() string {
 	cb, _ := self.eth.AccountManager().Coinbase()
-	return toHex(cb)
+	return common.ToHex(cb)
 }
 
 func (self *XEth) NumberToHuman(balance string) string {
@@ -213,7 +213,7 @@ func (self *XEth) NumberToHuman(balance string) string {
 func (self *XEth) StorageAt(addr, storageAddr string) string {
 	storage := self.State().SafeGet(addr).StorageString(storageAddr)
 
-	return toHex(storage.Bytes())
+	return common.ToHex(storage.Bytes())
 }
 
 func (self *XEth) BalanceAt(addr string) string {
@@ -225,7 +225,7 @@ func (self *XEth) TxCountAt(address string) int {
 }
 
 func (self *XEth) CodeAt(address string) string {
-	return toHex(self.State().SafeGet(address).Code())
+	return common.ToHex(self.State().SafeGet(address).Code())
 }
 
 func (self *XEth) IsContract(address string) bool {
@@ -238,7 +238,7 @@ func (self *XEth) SecretToAddress(key string) string {
 		return ""
 	}
 
-	return toHex(pair.Address())
+	return common.ToHex(pair.Address())
 }
 
 type KeyVal struct {
@@ -251,7 +251,7 @@ func (self *XEth) EachStorage(addr string) string {
 	object := self.State().SafeGet(addr)
 	it := object.Trie().Iterator()
 	for it.Next() {
-		values = append(values, KeyVal{toHex(it.Key), toHex(it.Value)})
+		values = append(values, KeyVal{common.ToHex(it.Key), common.ToHex(it.Value)})
 	}
 
 	valuesJson, err := json.Marshal(values)
@@ -265,7 +265,7 @@ func (self *XEth) EachStorage(addr string) string {
 func (self *XEth) ToAscii(str string) string {
 	padded := common.RightPadBytes([]byte(str), 32)
 
-	return "0x" + toHex(padded)
+	return "0x" + common.ToHex(padded)
 }
 
 func (self *XEth) FromAscii(str string) string {
@@ -325,7 +325,7 @@ func (self *XEth) Call(fromStr, toStr, valueStr, gasStr, gasPriceStr, dataStr st
 	vmenv := core.NewEnv(statedb, self.chainManager, msg, block)
 
 	res, err := vmenv.Call(msg.from, msg.to, msg.data, msg.gas, msg.gasPrice, msg.value)
-	return toHex(res), err
+	return common.ToHex(res), err
 }
 
 func (self *XEth) Transact(fromStr, toStr, valueStr, gasStr, gasPriceStr, codeStr string) (string, error) {