Add new key_store interface and two new key stores

* Add new generic key_store interface
* Add new plaintext key store storing unprotected keys on disk
* Add new encrypted key store storing encrypted keys on disk
* Add new entropy mixing function using OS and go runtime sources

.gitignore

@@ -10,3 +10,8 @@
 .DS_Store
 */**/.DS_Store
 .ethtest
+
+#*
+.#*
+*#
+*~

crypto/key.go

@@ -0,0 +1,205 @@
+/*
+	This file is part of go-ethereum
+
+	go-ethereum 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.
+
+	go-ethereum 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 General Public License for more details.
+
+	You should have received a copy of the GNU Lesser General Public License
+	along with go-ethereum.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/**
+ * @authors
+ * 	Gustav Simonsson <[email protected]>
+ * @date 2015
+ *
+ */
+
+package crypto
+
+import (
+	"bytes"
+	"code.google.com/p/go-uuid/uuid"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	crand "crypto/rand"
+	"encoding/binary"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"runtime"
+	"strings"
+	"time"
+)
+
+type Key struct {
+	Id    *uuid.UUID // Version 4 "random" for unique id not derived from key data
+	Flags [4]byte    // RFU
+	// we only store privkey as pubkey/address can be derived from it
+	// privkey in this struct is always in plaintext
+	PrivateKey *ecdsa.PrivateKey
+}
+
+type KeyPlainJSON struct {
+	Id         string
+	Flags      string
+	PrivateKey string
+}
+
+type CipherJSON struct {
+	Salt       string
+	IV         string
+	CipherText string
+}
+
+type KeyProtectedJSON struct {
+	Id     string
+	Flags  string
+	Crypto CipherJSON
+}
+
+func (k *Key) Address() []byte {
+	pubBytes := FromECDSAPub(&k.PrivateKey.PublicKey)
+	return Sha3(pubBytes)[12:]
+}
+
+func (k *Key) MarshalJSON() (j []byte, err error) {
+	stringStruct := KeyPlainJSON{
+		k.Id.String(),
+		hex.EncodeToString(k.Flags[:]),
+		hex.EncodeToString(FromECDSA(k.PrivateKey)),
+	}
+	j, _ = json.Marshal(stringStruct)
+	return
+}
+
+func (k *Key) UnmarshalJSON(j []byte) (err error) {
+	keyJSON := new(KeyPlainJSON)
+	err = json.Unmarshal(j, &keyJSON)
+	if err != nil {
+		return
+	}
+
+	u := new(uuid.UUID)
+	*u = uuid.Parse(keyJSON.Id)
+	if *u == nil {
+		err = errors.New("UUID parsing failed")
+		return
+	}
+	k.Id = u
+
+	flagsBytes, err := hex.DecodeString(keyJSON.Flags)
+	if err != nil {
+		return
+	}
+
+	PrivateKeyBytes, err := hex.DecodeString(keyJSON.PrivateKey)
+	if err != nil {
+		return
+	}
+
+	copy(k.Flags[:], flagsBytes[0:4])
+	k.PrivateKey = ToECDSA(PrivateKeyBytes)
+
+	return
+}
+
+func NewKey() *Key {
+	randBytes := GetEntropyCSPRNG(32)
+	reader := bytes.NewReader(randBytes)
+	_, x, y, err := elliptic.GenerateKey(S256(), reader)
+	if err != nil {
+		panic("key generation: elliptic.GenerateKey failed: " + err.Error())
+	}
+	privateKeyMarshalled := elliptic.Marshal(S256(), x, y)
+	privateKeyECDSA := ToECDSA(privateKeyMarshalled)
+
+	key := new(Key)
+	id := uuid.NewRandom()
+	key.Id = &id
+	// flags := new([4]byte)
+	// key.Flags = flags
+	key.PrivateKey = privateKeyECDSA
+	return key
+}
+
+// plain crypto/rand. this is /dev/urandom on Unix-like systems.
+func GetEntropyCSPRNG(n int) []byte {
+	mainBuff := make([]byte, n)
+	_, err := io.ReadFull(crand.Reader, mainBuff)
+	if err != nil {
+		panic("key generation: reading from crypto/rand failed: " + err.Error())
+	}
+	return mainBuff
+}
+
+// TODO: verify. Do not use until properly discussed.
+// we start with crypt/rand, then mix in additional sources of entropy.
+// These sources are from three types: OS, go runtime and ethereum client state.
+func GetEntropyTinFoilHat() []byte {
+	startTime := time.Now().UnixNano()
+	// for each source, we XOR in it's SHA3 hash.
+	mainBuff := GetEntropyCSPRNG(32)
+	// 1. OS entropy sources
+	startTimeBytes := make([]byte, 32)
+	binary.PutVarint(startTimeBytes, startTime)
+	startTimeHash := Sha3(startTimeBytes)
+	mix32Byte(mainBuff, startTimeHash)
+
+	pid := os.Getpid()
+	pidBytes := make([]byte, 32)
+	binary.PutUvarint(pidBytes, uint64(pid))
+	pidHash := Sha3(pidBytes)
+	mix32Byte(mainBuff, pidHash)
+
+	osEnv := os.Environ()
+	osEnvBytes := []byte(strings.Join(osEnv, ""))
+	osEnvHash := Sha3(osEnvBytes)
+	mix32Byte(mainBuff, osEnvHash)
+
+	// not all OS have hostname in env variables
+	osHostName, err := os.Hostname()
+	if err != nil {
+		osHostNameBytes := []byte(osHostName)
+		osHostNameHash := Sha3(osHostNameBytes)
+		mix32Byte(mainBuff, osHostNameHash)
+	}
+
+	// 2. go runtime entropy sources
+	memStats := new(runtime.MemStats)
+	runtime.ReadMemStats(memStats)
+	memStatsBytes := []byte(fmt.Sprintf("%v", memStats))
+	memStatsHash := Sha3(memStatsBytes)
+	mix32Byte(mainBuff, memStatsHash)
+
+	// 3. Mix in ethereum / client state
+	// TODO: list of network peers structs (IP, port, etc)
+	// TODO: merkle patricia tree root hash for world state and tx list
+
+	// 4. Yo dawg we heard you like entropy so we'll grab some entropy from how
+	//    long it took to grab the above entropy. And a yield, for good measure.
+	runtime.Gosched()
+	diffTime := time.Now().UnixNano() - startTime
+	diffTimeBytes := make([]byte, 32)
+	binary.PutVarint(diffTimeBytes, diffTime)
+	diffTimeHash := Sha3(diffTimeBytes)
+	mix32Byte(mainBuff, diffTimeHash)
+
+	return mainBuff
+}
+
+func mix32Byte(buff []byte, mixBuff []byte) []byte {
+	for i := 0; i < 32; i++ {
+		buff[i] ^= mixBuff[i]
+	}
+	return buff
+}