func decodePacket(buf []byte) (packet, NodeID, []byte, error) {
	if len(buf) < headSize+1 {
		return nil, NodeID{}, nil, errPacketTooSmall
	}
	hash, sig, sigdata := buf[:macSize], buf[macSize:headSize], buf[headSize:]
	shouldhash := crypto.Keccak256(buf[macSize:])
	if !bytes.Equal(hash, shouldhash) {
		return nil, NodeID{}, nil, errBadHash
	}
	fromID, err := recoverNodeID(crypto.Keccak256(buf[headSize:]), sig)
	if err != nil {
		return nil, NodeID{}, hash, err
	}
	var req packet
	switch ptype := sigdata[0]; ptype {
	case pingPacket:
		req = new(ping)
	case pongPacket:
		req = new(pong)
	case findnodePacket:
		req = new(findnode)
	case neighborsPacket:
		req = new(neighbors)
	default:
		return nil, fromID, hash, fmt.Errorf("unknown type: %d", ptype)
	}
	s := rlp.NewStream(bytes.NewReader(sigdata[1:]), 0)
	err = s.Decode(req)
	return req, fromID, hash, err
}

// secrets is called after the handshake is completed.
// It extracts the connection secrets from the handshake values.
func (h *encHandshake) secrets(auth, authResp []byte) (secrets, error) {
	ecdheSecret, err := h.randomPrivKey.GenerateShared(h.remoteRandomPub, sskLen, sskLen)
	if err != nil {
		return secrets{}, err
	}

	// derive base secrets from ephemeral key agreement
	sharedSecret := crypto.Keccak256(ecdheSecret, crypto.Keccak256(h.respNonce, h.initNonce))
	aesSecret := crypto.Keccak256(ecdheSecret, sharedSecret)
	s := secrets{
		RemoteID: h.remoteID,
		AES:      aesSecret,
		MAC:      crypto.Keccak256(ecdheSecret, aesSecret),
	}

	// setup sha3 instances for the MACs
	mac1 := sha3.NewKeccak256()
	mac1.Write(xor(s.MAC, h.respNonce))
	mac1.Write(auth)
	mac2 := sha3.NewKeccak256()
	mac2.Write(xor(s.MAC, h.initNonce))
	mac2.Write(authResp)
	if h.initiator {
		s.EgressMAC, s.IngressMAC = mac1, mac2
	} else {
		s.EgressMAC, s.IngressMAC = mac2, mac1
	}

	return s, nil
}

func storageMapping(addr, key []byte) []byte {
	data := make([]byte, 64)
	copy(data[0:32], key[0:32])
	copy(data[32:64], addr[0:32])
	sha := crypto.Keccak256(data)
	return sha
}

func ecrecoverFunc(in []byte) []byte {
	in = common.RightPadBytes(in, 128)
	// "in" is (hash, v, r, s), each 32 bytes
	// but for ecrecover we want (r, s, v)

	r := common.BytesToBig(in[64:96])
	s := common.BytesToBig(in[96:128])
	// Treat V as a 256bit integer
	vbig := common.Bytes2Big(in[32:64])
	v := byte(vbig.Uint64())

	// tighter sig s values in homestead only apply to tx sigs
	if !crypto.ValidateSignatureValues(v, r, s, false) {
		glog.V(logger.Detail).Infof("ECRECOVER error: v, r or s value invalid")
		return nil
	}

	// v needs to be at the end and normalized for libsecp256k1
	vbignormal := new(big.Int).Sub(vbig, big.NewInt(27))
	vnormal := byte(vbignormal.Uint64())
	rsv := append(in[64:128], vnormal)
	pubKey, err := crypto.Ecrecover(in[:32], rsv)
	// make sure the public key is a valid one
	if err != nil {
		glog.V(logger.Detail).Infoln("ECRECOVER error: ", err)
		return nil
	}

	// the first byte of pubkey is bitcoin heritage
	return common.LeftPadBytes(crypto.Keccak256(pubKey[1:])[12:], 32)
}

// sets defaults on the config
func setDefaults(cfg *Config) {
	if cfg.RuleSet == nil {
		cfg.RuleSet = ruleSet{}
	}

	if cfg.Difficulty == nil {
		cfg.Difficulty = new(big.Int)
	}
	if cfg.Time == nil {
		cfg.Time = big.NewInt(time.Now().Unix())
	}
	if cfg.GasLimit == nil {
		cfg.GasLimit = new(big.Int).Set(common.MaxBig)
	}
	if cfg.GasPrice == nil {
		cfg.GasPrice = new(big.Int)
	}
	if cfg.Value == nil {
		cfg.Value = new(big.Int)
	}
	if cfg.BlockNumber == nil {
		cfg.BlockNumber = new(big.Int)
	}
	if cfg.GetHashFn == nil {
		cfg.GetHashFn = func(n uint64) common.Hash {
			return common.BytesToHash(crypto.Keccak256([]byte(new(big.Int).SetUint64(n).String())))
		}
	}
}

// storeProof stores the new trie nodes obtained from a merkle proof in the database
func storeProof(db ethdb.Database, proof []rlp.RawValue) {
	for _, buf := range proof {
		hash := crypto.Keccak256(buf)
		val, _ := db.Get(hash)
		if val == nil {
			db.Put(hash, buf)
		}
	}
}

func (msg *authMsgV4) sealPlain(h *encHandshake) ([]byte, error) {
	buf := make([]byte, authMsgLen)
	n := copy(buf, msg.Signature[:])
	n += copy(buf[n:], crypto.Keccak256(exportPubkey(&h.randomPrivKey.PublicKey)))
	n += copy(buf[n:], msg.InitiatorPubkey[:])
	n += copy(buf[n:], msg.Nonce[:])
	buf[n] = 0 // token-flag
	return ecies.Encrypt(rand.Reader, h.remotePub, buf, nil, nil)
}

// Id returns the canonical representation of the event's signature used by the
// abi definition to identify event names and types.
func (e Event) Id() common.Hash {
	types := make([]string, len(e.Inputs))
	i := 0
	for _, input := range e.Inputs {
		types[i] = input.Type.String()
		i++
	}
	return common.BytesToHash(crypto.Keccak256([]byte(fmt.Sprintf("%v(%v)", e.Name, strings.Join(types, ",")))))
}

func SaveInfo(info *ContractInfo, filename string) (contenthash common.Hash, err error) {
	infojson, err := json.Marshal(info)
	if err != nil {
		return
	}
	contenthash = common.BytesToHash(crypto.Keccak256(infojson))
	err = ioutil.WriteFile(filename, infojson, 0600)
	return
}

func TestRLPXFrameFake(t *testing.T) {
	buf := new(bytes.Buffer)
	hash := fakeHash([]byte{1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1})
	rw := newRLPXFrameRW(buf, secrets{
		AES:        crypto.Keccak256(),
		MAC:        crypto.Keccak256(),
		IngressMAC: hash,
		EgressMAC:  hash,
	})

	golden := unhex(`
00828ddae471818bb0bfa6b551d1cb42
01010101010101010101010101010101
ba628a4ba590cb43f7848f41c4382885
01010101010101010101010101010101
`)

	// Check WriteMsg. This puts a message into the buffer.
	if err := Send(rw, 8, []uint{1, 2, 3, 4}); err != nil {
		t.Fatalf("WriteMsg error: %v", err)
	}
	written := buf.Bytes()
	if !bytes.Equal(written, golden) {
		t.Fatalf("output mismatch:\n  got:  %x\n  want: %x", written, golden)
	}

	// Check ReadMsg. It reads the message encoded by WriteMsg, which
	// is equivalent to the golden message above.
	msg, err := rw.ReadMsg()
	if err != nil {
		t.Fatalf("ReadMsg error: %v", err)
	}
	if msg.Size != 5 {
		t.Errorf("msg size mismatch: got %d, want %d", msg.Size, 5)
	}
	if msg.Code != 8 {
		t.Errorf("msg code mismatch: got %d, want %d", msg.Code, 8)
	}
	payload, _ := ioutil.ReadAll(msg.Payload)
	wantPayload := unhex("C401020304")
	if !bytes.Equal(payload, wantPayload) {
		t.Errorf("msg payload mismatch:\ngot  %x\nwant %x", payload, wantPayload)
	}
}

// DeliverNodeData injects a node state data retrieval response into the queue.
// The method returns the number of node state entries originally requested, and
// the number of them actually accepted from the delivery.
func (q *queue) DeliverNodeData(id string, data [][]byte, callback func(error, int)) (int, error) {
	q.lock.Lock()
	defer q.lock.Unlock()

	// Short circuit if the data was never requested
	request := q.statePendPool[id]
	if request == nil {
		return 0, errNoFetchesPending
	}
	stateReqTimer.UpdateSince(request.Time)
	delete(q.statePendPool, id)

	// If no data was retrieved, mark their hashes as unavailable for the origin peer
	if len(data) == 0 {
		for hash, _ := range request.Hashes {
			request.Peer.MarkLacking(hash)
		}
	}
	// Iterate over the downloaded data and verify each of them
	accepted, errs := 0, make([]error, 0)
	process := []trie.SyncResult{}
	for _, blob := range data {
		// Skip any state trie entries that were not requested
		hash := common.BytesToHash(crypto.Keccak256(blob))
		if _, ok := request.Hashes[hash]; !ok {
			errs = append(errs, fmt.Errorf("non-requested state data %x", hash))
			continue
		}
		// Inject the next state trie item into the processing queue
		process = append(process, trie.SyncResult{Hash: hash, Data: blob})
		accepted++

		delete(request.Hashes, hash)
		delete(q.stateTaskPool, hash)
	}
	// Start the asynchronous node state data injection
	atomic.AddInt32(&q.stateProcessors, 1)
	go func() {
		defer atomic.AddInt32(&q.stateProcessors, -1)
		q.deliverNodeData(process, callback)
	}()
	// Return all failed or missing fetches to the queue
	for hash, index := range request.Hashes {
		q.stateTaskQueue.Push(hash, float32(index))
	}
	// If none of the data items were good, it's a stale delivery
	switch {
	case len(errs) == 0:
		return accepted, nil
	case len(errs) == len(request.Hashes):
		return accepted, errStaleDelivery
	default:
		return accepted, fmt.Errorf("multiple failures: %v", errs)
	}
}

func encodePacket(priv *ecdsa.PrivateKey, ptype byte, req interface{}) ([]byte, error) {
	b := new(bytes.Buffer)
	b.Write(headSpace)
	b.WriteByte(ptype)
	if err := rlp.Encode(b, req); err != nil {
		glog.V(logger.Error).Infoln("error encoding packet:", err)
		return nil, err
	}
	packet := b.Bytes()
	sig, err := crypto.Sign(crypto.Keccak256(packet[headSize:]), priv)
	if err != nil {
		glog.V(logger.Error).Infoln("could not sign packet:", err)
		return nil, err
	}
	copy(packet[macSize:], sig)
	// add the hash to the front. Note: this doesn't protect the
	// packet in any way. Our public key will be part of this hash in
	// The future.
	copy(packet, crypto.Keccak256(packet[macSize:]))
	return packet, nil
}

func bloom9(b []byte) *big.Int {
	b = crypto.Keccak256(b[:])

	r := new(big.Int)

	for i := 0; i < 6; i += 2 {
		t := big.NewInt(1)
		b := (uint(b[i+1]) + (uint(b[i]) << 8)) & 2047
		r.Or(r, t.Lsh(t, b))
	}

	return r
}

func doFrom(tx *Transaction, homestead bool) (common.Address, error) {
	if from := tx.from.Load(); from != nil {
		return from.(common.Address), nil
	}
	pubkey, err := tx.publicKey(homestead)
	if err != nil {
		return common.Address{}, err
	}
	var addr common.Address
	copy(addr[:], crypto.Keccak256(pubkey[1:])[12:])
	tx.from.Store(addr)
	return addr, nil
}

func (self *NatSpec) makeAbi2method(abiKey [8]byte) (meth *method) {
	for signature, m := range self.userDoc.Methods {
		name := strings.Split(signature, "(")[0]
		hash := []byte(common.Bytes2Hex(crypto.Keccak256([]byte(signature))))
		var key [8]byte
		copy(key[:], hash[:8])
		if bytes.Equal(key[:], abiKey[:]) {
			meth = m
			mexp.name = name
			return
		}
	}
	return
}

func TestSecureGetKey(t *testing.T) {
	trie := newEmptySecure()
	trie.Update([]byte("foo"), []byte("bar"))

	key := []byte("foo")
	value := []byte("bar")
	seckey := crypto.Keccak256(key)

	if !bytes.Equal(trie.Get(key), value) {
		t.Errorf("Get did not return bar")
	}
	if k := trie.GetKey(seckey); !bytes.Equal(k, key) {
		t.Errorf("GetKey returned %q, want %q", k, key)
	}
}

// Seal closes the envelope by spending the requested amount of time as a proof
// of work on hashing the data.
func (self *Envelope) Seal(pow time.Duration) {
	d := make([]byte, 64)
	copy(d[:32], self.rlpWithoutNonce())

	finish, bestBit := time.Now().Add(pow).UnixNano(), 0
	for nonce := uint32(0); time.Now().UnixNano() < finish; {
		for i := 0; i < 1024; i++ {
			binary.BigEndian.PutUint32(d[60:], nonce)

			firstBit := common.FirstBitSet(common.BigD(crypto.Keccak256(d)))
			if firstBit > bestBit {
				self.Nonce, bestBit = nonce, firstBit
			}
			nonce++
		}
	}
}

func TestMethodSignature(t *testing.T) {
	String, _ := NewType("string")
	m := Method{"foo", false, []Argument{Argument{"bar", String, false}, Argument{"baz", String, false}}, nil}
	exp := "foo(string,string)"
	if m.Sig() != exp {
		t.Error("signature mismatch", exp, "!=", m.Sig())
	}

	idexp := crypto.Keccak256([]byte(exp))[:4]
	if !bytes.Equal(m.Id(), idexp) {
		t.Errorf("expected ids to match %x != %x", m.Id(), idexp)
	}

	uintt, _ := NewType("uint")
	m = Method{"foo", false, []Argument{Argument{"bar", uintt, false}}, nil}
	exp = "foo(uint256)"
	if m.Sig() != exp {
		t.Error("signature mismatch", exp, "!=", m.Sig())
	}
}

func decryptPreSaleKey(fileContent []byte, password string) (key *Key, err error) {
	preSaleKeyStruct := struct {
		EncSeed string
		EthAddr string
		Email   string
		BtcAddr string
	}{}
	err = json.Unmarshal(fileContent, &preSaleKeyStruct)
	if err != nil {
		return nil, err
	}
	encSeedBytes, err := hex.DecodeString(preSaleKeyStruct.EncSeed)
	iv := encSeedBytes[:16]
	cipherText := encSeedBytes[16:]
	/*
		See https://github.com/ethereum/pyethsaletool

		pyethsaletool generates the encryption key from password by
		2000 rounds of PBKDF2 with HMAC-SHA-256 using password as salt (:().
		16 byte key length within PBKDF2 and resulting key is used as AES key
	*/
	passBytes := []byte(password)
	derivedKey := pbkdf2.Key(passBytes, passBytes, 2000, 16, sha256.New)
	plainText, err := aesCBCDecrypt(derivedKey, cipherText, iv)
	if err != nil {
		return nil, err
	}
	ethPriv := crypto.Keccak256(plainText)
	ecKey := crypto.ToECDSA(ethPriv)
	key = &Key{
		Id:         nil,
		Address:    crypto.PubkeyToAddress(ecKey.PublicKey),
		PrivateKey: ecKey,
	}
	derivedAddr := hex.EncodeToString(key.Address.Bytes()) // needed because .Hex() gives leading "0x"
	expectedAddr := preSaleKeyStruct.EthAddr
	if derivedAddr != expectedAddr {
		err = fmt.Errorf("decrypted addr '%s' not equal to expected addr '%s'", derivedAddr, expectedAddr)
	}
	return key, err
}

// also called by admin.contractInfo.get
func FetchDocsForContract(contractAddress string, xeth *xexp.XEth, client *httpclient.HTTPClient) (content []byte, err error) {
	// retrieve contract hash from state
	codehex := xexp.CodeAt(contractAddress)
	codeb := xexp.CodeAtBytes(contractAddress)

	if codehex == "0x" {
		err = fmt.Errorf("contract (%v) not found", contractAddress)
		return
	}
	codehash := common.BytesToHash(crypto.Keccak256(codeb))
	// set up nameresolver with natspecreg + urlhint contract addresses
	reg := registrar.New(xeth)

	// resolve host via HashReg/UrlHint Resolver
	hash, err := reg.HashToHash(codehash)
	if err != nil {
		return
	}
	if client.HasScheme("bzz") {
		content, err = client.Get("bzz://"+hash.Hex()[2:], "")
		if err == nil { // non-fatal
			return
		}
		err = nil
		//falling back to urlhint
	}

	uri, err := reg.HashToUrl(hash)
	if err != nil {
		return
	}

	// get content via http client and authenticate content using hash
	content, err = client.GetAuthContent(uri, hash)
	if err != nil {
		return
	}
	return
}