Base wallet implementation (#35)

* Initial draft of the neo-go wallet * Cleanup + more test for util package * integrated wallet into neo-cli partially * base wallet implementation + smartcontract code.
2018-03-02 16:24:09 +01:00 · 2018-03-02 16:24:09 +01:00 · f3f6662fc9
commit f3f6662fc9
parent 942650dd8b
33 changed files with 1754 additions and 87 deletions
--- a/Gopkg.lock
+++ b/Gopkg.lock
@ -2,19 +2,10 @@


 [[projects]]
-  name = "github.com/CityOfZion/neo-go"
-  packages = [
-    "cli/server",
-    "cli/smartcontract",
-    "pkg/core",
-    "pkg/network",
-    "pkg/network/payload",
-    "pkg/util",
-    "pkg/vm",
-    "pkg/vm/compiler"
-  ]
-  revision = "8fe079ec8ebb83ce53d6f1535bfe513271231958"
-  version = "0.11.0"
+  branch = "master"
+  name = "github.com/anthdm/rfc6979"
+  packages = ["."]
+  revision = "6a90f24967ebb1aa57b22f74a13dbb3faad8cf3d"

 [[projects]]
  branch = "master"
@ -47,9 +38,42 @@
  revision = "cfb38830724cc34fedffe9a2a29fb54fa9169cd1"
  version = "v1.20.0"

+[[projects]]
+  branch = "master"
+  name = "golang.org/x/crypto"
+  packages = [
+    "pbkdf2",
+    "ripemd160",
+    "scrypt"
+  ]
+  revision = "8c653846df49742c4c85ec37e5d9f8d3ba657895"
+
+[[projects]]
+  name = "golang.org/x/text"
+  packages = [
+    "internal/gen",
+    "internal/triegen",
+    "internal/ucd",
+    "transform",
+    "unicode/cldr",
+    "unicode/norm"
+  ]
+  revision = "f21a4dfb5e38f5895301dc265a8def02365cc3d0"
+  version = "v0.3.0"
+
+[[projects]]
+  branch = "master"
+  name = "golang.org/x/tools"
+  packages = [
+    "go/ast/astutil",
+    "go/buildutil",
+    "go/loader"
+  ]
+  revision = "73e16cff9e0d4a802937444bebb562458548241d"
+
 [solve-meta]
  analyzer-name = "dep"
  analyzer-version = 1
-  inputs-digest = "ac1d2cc7e9e2cb3985a84af2b75ad9fd78a3b8278abb6d5f7b6dd2210df7c6a2"
+  inputs-digest = "74c6b0a11057b8c0fd68342f85e010e323cda6407bec2a889f161b5890928aaf"
  solver-name = "gps-cdcl"
  solver-version = 1
--- a/Gopkg.toml
+++ b/Gopkg.toml
@ -35,3 +35,15 @@
 [prune]
  go-tests = true
  unused-packages = true
+
+[[constraint]]
+  branch = "master"
+  name = "golang.org/x/crypto"
+
+[[constraint]]
+  branch = "master"
+  name = "github.com/anthdm/rfc6979"
+
+[[constraint]]
+  name = "golang.org/x/text"
+  version = "0.3.0"
--- a/2
+++ b/2
@ -1 +1 @@
-0.18.0
+0.19.0
--- a/cli/main.go
+++ b/cli/main.go
@ -5,6 +5,7 @@ import (

 	"github.com/CityOfZion/neo-go/cli/server"
 	"github.com/CityOfZion/neo-go/cli/smartcontract"
+	"github.com/CityOfZion/neo-go/cli/wallet"
 	"github.com/urfave/cli"
 )

@ -16,6 +17,7 @@ func main() {
 	ctl.Commands = []cli.Command{
 		server.NewCommand(),
 		smartcontract.NewCommand(),
+		wallet.NewCommand(),
 	}

 	ctl.Run(os.Args)
--- a/cli/server/server.go
+++ b/cli/server/server.go
@ -7,7 +7,7 @@ import (
 	"github.com/urfave/cli"
 )

-// NewCommand creates a new Node command
+// NewCommand creates a new Node command.
 func NewCommand() cli.Command {
 	return cli.Command{
 		Name:   "node",
--- a/cli/wallet/wallet.go
+++ b/cli/wallet/wallet.go
@ -0,0 +1,116 @@
+package wallet
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/CityOfZion/neo-go/pkg/wallet"
+	"github.com/urfave/cli"
+)
+
+var (
+	errNoPath          = errors.New("Target path where the wallet should be stored is mandatory and should be passed using (--path, -p) flags.")
+	errPhraseMissmatch = errors.New("The entered passphrases do not match. Maybe you have misspelled them?")
+)
+
+// NewComand creates a new Wallet command.
+func NewCommand() cli.Command {
+	return cli.Command{
+		Name:  "wallet",
+		Usage: "create, open and manage a NEO wallet",
+		Subcommands: []cli.Command{
+			{
+				Name:   "create",
+				Usage:  "create a new wallet",
+				Action: createWallet,
+				Flags: []cli.Flag{
+					cli.StringFlag{
+						Name:  "path, p",
+						Usage: "Target location of the wallet file.",
+					},
+					cli.BoolFlag{
+						Name:  "account, a",
+						Usage: "Create a new account",
+					},
+				},
+			},
+			{
+				Name:   "open",
+				Usage:  "open a existing NEO wallet",
+				Action: openWallet,
+				Flags: []cli.Flag{
+					cli.StringFlag{
+						Name:  "path, p",
+						Usage: "Target location of the wallet file.",
+					},
+				},
+			},
+		},
+	}
+}
+
+func openWallet(ctx *cli.Context) error {
+	return nil
+}
+
+func createWallet(ctx *cli.Context) error {
+	path := ctx.String("path")
+	if len(path) == 0 {
+		return cli.NewExitError(errNoPath, 1)
+	}
+	wall, err := wallet.NewWallet(path)
+	if err != nil {
+		return cli.NewExitError(err, 1)
+	}
+	if err := wall.Save(); err != nil {
+		return cli.NewExitError(err, 1)
+	}
+
+	if ctx.Bool("account") {
+		if err := createAccount(ctx, wall); err != nil {
+			return cli.NewExitError(err, 1)
+		}
+	}
+
+	dumpWallet(wall)
+	fmt.Printf("wallet succesfully created, file location is %s\n", wall.Path())
+	return nil
+}
+
+func createAccount(ctx *cli.Context, wall *wallet.Wallet) error {
+	var (
+		rawName,
+		rawPhrase,
+		rawPhraseCheck []byte
+	)
+	buf := bufio.NewReader(os.Stdin)
+	fmt.Print("Enter the name of the account > ")
+	rawName, _ = buf.ReadBytes('\n')
+	fmt.Print("Enter passphrase > ")
+	rawPhrase, _ = buf.ReadBytes('\n')
+	fmt.Print("Confirm passphrase > ")
+	rawPhraseCheck, _ = buf.ReadBytes('\n')
+
+	// Clean data
+	var (
+		name        = strings.TrimRight(string(rawName), "\n")
+		phrase      = strings.TrimRight(string(rawPhrase), "\n")
+		phraseCheck = strings.TrimRight(string(rawPhraseCheck), "\n")
+	)
+
+	if phrase != phraseCheck {
+		return errPhraseMissmatch
+	}
+
+	return wall.CreateAccount(name, phrase)
+}
+
+func dumpWallet(wall *wallet.Wallet) {
+	b, _ := wall.JSON()
+	fmt.Println("")
+	fmt.Println(string(b))
+	fmt.Println("")
+}
--- a/pkg/core/block.go
+++ b/pkg/core/block.go
@ -84,7 +84,7 @@ func (b *BlockBase) Hash() (hash util.Uint256, err error) {

 	// Double hash the encoded fields.
 	hash = sha256.Sum256(buf.Bytes())
-	hash = sha256.Sum256(hash.ToSlice())
+	hash = sha256.Sum256(hash.Bytes())
 	return hash, nil
 }

--- a/pkg/core/blockchain.go
+++ b/pkg/core/blockchain.go
@ -67,7 +67,7 @@ func (bc *Blockchain) genesisBlock() *Block {
 	// togheter much faster.
 	// For more information about the genesis block:
 	// https://neotracker.io/block/height/0
-	mr, _ := util.Uint256DecodeFromString("803ff4abe3ea6533bcc0be574efa02f83ae8fdc651c879056b0d9be336c01bf4")
+	mr, _ := util.Uint256DecodeString("803ff4abe3ea6533bcc0be574efa02f83ae8fdc651c879056b0d9be336c01bf4")

 	return &Block{
 		BlockBase: BlockBase{
@ -171,7 +171,7 @@ func (bc *Blockchain) processHeader(h *Header, batch Batch) error {
 		return err
 	}

-	preBlock := preDataBlock.add(hash.ToSliceReverse())
+	preBlock := preDataBlock.add(hash.BytesReverse())
 	batch[&preBlock] = buf.Bytes()
 	preHeader := preSYSCurrentHeader.toSlice()
 	batch[&preHeader] = hashAndIndexToBytes(hash, h.Index)
@ -209,5 +209,5 @@ func (bc *Blockchain) HeaderHeight() uint32 {
 func hashAndIndexToBytes(h util.Uint256, index uint32) []byte {
 	buf := make([]byte, 4)
 	binary.LittleEndian.PutUint32(buf, index)
-	return append(h.ToSliceReverse(), buf...)
+	return append(h.BytesReverse(), buf...)
 }
--- a/pkg/core/blockchain_test.go
+++ b/pkg/core/blockchain_test.go
@ -9,7 +9,7 @@ import (
 )

 func TestNewBlockchain(t *testing.T) {
-	startHash, _ := util.Uint256DecodeFromString("996e37358dc369912041f966f8c5d8d3a8255ba5dcbd3447f8a82b55db869099")
+	startHash, _ := util.Uint256DecodeString("996e37358dc369912041f966f8c5d8d3a8255ba5dcbd3447f8a82b55db869099")
 	bc := NewBlockchain(nil, nil, startHash)

 	want := uint32(0)
@ -28,7 +28,7 @@ func TestNewBlockchain(t *testing.T) {
 }

 func TestAddHeaders(t *testing.T) {
-	startHash, _ := util.Uint256DecodeFromString("996e37358dc369912041f966f8c5d8d3a8255ba5dcbd3447f8a82b55db869099")
+	startHash, _ := util.Uint256DecodeString("996e37358dc369912041f966f8c5d8d3a8255ba5dcbd3447f8a82b55db869099")
 	bc := NewBlockchain(NewMemoryStore(), log.New(os.Stdout, "", 0), startHash)

 	h1 := &Header{BlockBase: BlockBase{Version: 0, Index: 1, Script: &Witness{}}}
--- a/pkg/crypto/aes256.go
+++ b/pkg/crypto/aes256.go
@ -0,0 +1,93 @@
+package crypto
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+)
+
+// AESEncrypt encrypts the key with the given source.
+func AESEncrypt(src, key []byte) ([]byte, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	ecb := newECBEncrypter(block)
+	out := make([]byte, len(src))
+	ecb.CryptBlocks(out, src)
+
+	return out, nil
+}
+
+// AESDecrypt decrypts the encrypted source with the given key.
+func AESDecrypt(crypted, key []byte) ([]byte, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	blockMode := newECBDecrypter(block)
+	out := make([]byte, len(crypted))
+	blockMode.CryptBlocks(out, crypted)
+	return out, nil
+}
+
+type ecb struct {
+	b         cipher.Block
+	blockSize int
+}
+
+func newECB(b cipher.Block) *ecb {
+	return &ecb{
+		b:         b,
+		blockSize: b.BlockSize(),
+	}
+}
+
+type ecbEncrypter ecb
+
+func newECBEncrypter(b cipher.Block) cipher.BlockMode {
+	return (*ecbEncrypter)(newECB(b))
+}
+
+func (ecb *ecbEncrypter) BlockSize() int {
+	return ecb.blockSize
+}
+
+func (ecb *ecbEncrypter) CryptBlocks(dst, src []byte) {
+	if len(src)%ecb.blockSize != 0 {
+		panic("crypto/cipher: input not full blocks")
+	}
+	if len(dst) < len(src) {
+		panic("crypto/cipher: output smaller than input")
+	}
+	for len(src) > 0 {
+		ecb.b.Encrypt(dst, src[:ecb.blockSize])
+		src = src[ecb.blockSize:]
+		dst = dst[ecb.blockSize:]
+	}
+}
+
+type ecbDecrypter ecb
+
+func newECBDecrypter(b cipher.Block) cipher.BlockMode {
+	return (*ecbDecrypter)(newECB(b))
+}
+
+func (ecb ecbDecrypter) BlockSize() int {
+	return ecb.blockSize
+}
+
+func (ecb *ecbDecrypter) CryptBlocks(dst, src []byte) {
+	if len(src)%ecb.blockSize != 0 {
+		panic("crypto/cipher: input not full blocks")
+	}
+	if len(dst) < len(src) {
+		panic("crypto/cipher: output smaller than input")
+	}
+	for len(src) > 0 {
+		ecb.b.Decrypt(dst, src[:ecb.blockSize])
+		src = src[ecb.blockSize:]
+		dst = dst[ecb.blockSize:]
+	}
+}
--- a/pkg/crypto/base58.go
+++ b/pkg/crypto/base58.go
@ -0,0 +1,130 @@
+package crypto
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"fmt"
+	"math/big"
+)
+
+const prefix rune = '1'
+
+var decodeMap = map[rune]int64{
+	'1': 0, '2': 1, '3': 2, '4': 3, '5': 4,
+	'6': 5, '7': 6, '8': 7, '9': 8, 'A': 9,
+	'B': 10, 'C': 11, 'D': 12, 'E': 13, 'F': 14,
+	'G': 15, 'H': 16, 'J': 17, 'K': 18, 'L': 19,
+	'M': 20, 'N': 21, 'P': 22, 'Q': 23, 'R': 24,
+	'S': 25, 'T': 26, 'U': 27, 'V': 28, 'W': 29,
+	'X': 30, 'Y': 31, 'Z': 32, 'a': 33, 'b': 34,
+	'c': 35, 'd': 36, 'e': 37, 'f': 38, 'g': 39,
+	'h': 40, 'i': 41, 'j': 42, 'k': 43, 'm': 44,
+	'n': 45, 'o': 46, 'p': 47, 'q': 48, 'r': 49,
+	's': 50, 't': 51, 'u': 52, 'v': 53, 'w': 54,
+	'x': 55, 'y': 56, 'z': 57,
+}
+
+// Base58Decode decodes the base58 encoded string.
+func Base58Decode(s string) ([]byte, error) {
+	var (
+		startIndex = 0
+		zero       = 0
+	)
+	for i, c := range s {
+		if c == prefix {
+			zero++
+		} else {
+			startIndex = i
+			break
+		}
+	}
+
+	var (
+		n   = big.NewInt(0)
+		div = big.NewInt(58)
+	)
+	for _, c := range s[startIndex:] {
+		charIndex, ok := decodeMap[c]
+		if !ok {
+			return nil, fmt.Errorf(
+				"invalid character '%c' when decoding this base58 string: '%s'", c, s,
+			)
+		}
+		n.Add(n.Mul(n, div), big.NewInt(charIndex))
+	}
+
+	out := n.Bytes()
+	buf := make([]byte, (zero + len(out)))
+	copy(buf[zero:], out[:])
+
+	return buf, nil
+}
+
+// Base58Encode encodes a byte slice to be a base58 encoded string.
+func Base58Encode(bytes []byte) string {
+	var (
+		lookupTable = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
+		x           = new(big.Int).SetBytes(bytes)
+		r           = new(big.Int)
+		m           = big.NewInt(58)
+		zero        = big.NewInt(0)
+		encoded     string
+	)
+
+	for x.Cmp(zero) > 0 {
+		x.QuoRem(x, m, r)
+		encoded = string(lookupTable[r.Int64()]) + encoded
+	}
+
+	return encoded
+}
+
+func Base58CheckDecode(s string) (b []byte, err error) {
+	b, err = Base58Decode(s)
+	if err != nil {
+		return nil, err
+	}
+
+	for i := 0; i < len(s); i++ {
+		if s[i] != '1' {
+			break
+		}
+		b = append([]byte{0x00}, b...)
+	}
+
+	if len(b) < 5 {
+		return nil, fmt.Errorf("Invalid base-58 check string: missing checksum.")
+	}
+
+	sha := sha256.New()
+	sha.Write(b[:len(b)-4])
+	hash := sha.Sum(nil)
+
+	sha.Reset()
+	sha.Write(hash)
+	hash = sha.Sum(nil)
+
+	if bytes.Compare(hash[0:4], b[len(b)-4:]) != 0 {
+		return nil, fmt.Errorf("Invalid base-58 check string: invalid checksum.")
+	}
+
+	// Strip the 4 byte long hash.
+	b = b[:len(b)-4]
+
+	return b, nil
+}
+
+// Base58checkEncode encodes b into a base-58 check encoded string.
+func Base58CheckEncode(b []byte) string {
+	sha := sha256.New()
+	sha.Write(b)
+	hash := sha.Sum(nil)
+
+	sha.Reset()
+	sha.Write(hash)
+	hash = sha.Sum(nil)
+
+	b = append(b, hash[0:4]...)
+
+	return Base58Encode(b)
+}
--- a/pkg/crypto/elliptic_curve.go
+++ b/pkg/crypto/elliptic_curve.go
@ -0,0 +1,196 @@
+package crypto
+
+// Original work completed by @vsergeev: https://github.com/vsergeev/btckeygenie
+// Expanded and tweaked upon here under MIT license.
+
+import (
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"math/big"
+)
+
+type (
+	// EllipticCurve represents the parameters of a short Weierstrass equation elliptic
+	// curve.
+	EllipticCurve struct {
+		A *big.Int
+		B *big.Int
+		P *big.Int
+		G EllipticCurvePoint
+		N *big.Int
+		H *big.Int
+	}
+
+	// EllipticCurveEllipticCurvePoint represents a point on the EllipticCurve.
+	EllipticCurvePoint struct {
+		X *big.Int
+		Y *big.Int
+	}
+)
+
+// NewEllipticCurve returns a ready to use EllipticCurve with preconfigured
+// fields for the NEO protocol.
+func NewEllipticCurve() EllipticCurve {
+	c := EllipticCurve{}
+
+	c.P, _ = new(big.Int).SetString(
+		"FFFFFFFF00000001000000000000000000000000FFFFFFFFFFFFFFFFFFFFFFFF", 16,
+	)
+	c.A, _ = new(big.Int).SetString(
+		"FFFFFFFF00000001000000000000000000000000FFFFFFFFFFFFFFFFFFFFFFFC", 16,
+	)
+	c.B, _ = new(big.Int).SetString(
+		"5AC635D8AA3A93E7B3EBBD55769886BC651D06B0CC53B0F63BCE3C3E27D2604B", 16,
+	)
+	c.G.X, _ = new(big.Int).SetString(
+		"6B17D1F2E12C4247F8BCE6E563A440F277037D812DEB33A0F4A13945D898C296", 16,
+	)
+	c.G.Y, _ = new(big.Int).SetString(
+		"4FE342E2FE1A7F9B8EE7EB4A7C0F9E162BCE33576B315ECECBB6406837BF51F5", 16,
+	)
+	c.N, _ = new(big.Int).SetString(
+		"FFFFFFFF00000000FFFFFFFFFFFFFFFFBCE6FAADA7179E84F3B9CAC2FC632551", 16,
+	)
+	c.H, _ = new(big.Int).SetString("01", 16)
+
+	return c
+}
+
+func (p *EllipticCurvePoint) format() string {
+	if p.X == nil && p.Y == nil {
+		return "(inf,inf)"
+	}
+	bx := hex.EncodeToString(p.X.Bytes())
+	by := hex.EncodeToString(p.Y.Bytes())
+	return fmt.Sprintf("(%s, %s)", bx, by)
+}
+
+// IsInfinity checks if point P is infinity on EllipticCurve ec.
+func (c *EllipticCurve) IsInfinity(P EllipticCurvePoint) bool {
+	if P.X == nil && P.Y == nil {
+		return true
+	}
+	return false
+}
+
+// IsOnCurve checks if point P is on EllipticCurve ec.
+func (c *EllipticCurve) IsOnCurve(P EllipticCurvePoint) bool {
+	if c.IsInfinity(P) {
+		return false
+	}
+	lhs := mulMod(P.Y, P.Y, c.P)
+	rhs := addMod(
+		addMod(
+			expMod(P.X, big.NewInt(3), c.P),
+			mulMod(c.A, P.X, c.P), c.P),
+		c.B, c.P)
+
+	if lhs.Cmp(rhs) == 0 {
+		return true
+	}
+	return false
+}
+
+// Add computes R = P + Q on EllipticCurve ec.
+func (c *EllipticCurve) Add(P, Q EllipticCurvePoint) (R EllipticCurvePoint) {
+	// See rules 1-5 on SEC1 pg.7 http://www.secg.org/collateral/sec1_final.pdf
+	if c.IsInfinity(P) && c.IsInfinity(Q) {
+		R.X = nil
+		R.Y = nil
+	} else if c.IsInfinity(P) {
+		R.X = new(big.Int).Set(Q.X)
+		R.Y = new(big.Int).Set(Q.Y)
+	} else if c.IsInfinity(Q) {
+		R.X = new(big.Int).Set(P.X)
+		R.Y = new(big.Int).Set(P.Y)
+	} else if P.X.Cmp(Q.X) == 0 && addMod(P.Y, Q.Y, c.P).Sign() == 0 {
+		R.X = nil
+		R.Y = nil
+	} else if P.X.Cmp(Q.X) == 0 && P.Y.Cmp(Q.Y) == 0 && P.Y.Sign() != 0 {
+		num := addMod(
+			mulMod(big.NewInt(3),
+				mulMod(P.X, P.X, c.P), c.P),
+			c.A, c.P)
+		den := invMod(mulMod(big.NewInt(2), P.Y, c.P), c.P)
+		lambda := mulMod(num, den, c.P)
+		R.X = subMod(
+			mulMod(lambda, lambda, c.P),
+			mulMod(big.NewInt(2), P.X, c.P),
+			c.P)
+		R.Y = subMod(
+			mulMod(lambda, subMod(P.X, R.X, c.P), c.P),
+			P.Y, c.P)
+	} else if P.X.Cmp(Q.X) != 0 {
+		num := subMod(Q.Y, P.Y, c.P)
+		den := invMod(subMod(Q.X, P.X, c.P), c.P)
+		lambda := mulMod(num, den, c.P)
+		R.X = subMod(
+			subMod(
+				mulMod(lambda, lambda, c.P),
+				P.X, c.P),
+			Q.X, c.P)
+		R.Y = subMod(
+			mulMod(lambda,
+				subMod(P.X, R.X, c.P), c.P),
+			P.Y, c.P)
+	} else {
+		panic(fmt.Sprintf("Unsupported point addition: %v + %v", P.format(), Q.format()))
+	}
+
+	return R
+}
+
+// ScalarMult computes Q = k * P on EllipticCurve ec.
+func (c *EllipticCurve) ScalarMult(k *big.Int, P EllipticCurvePoint) (Q EllipticCurvePoint) {
+	// Implementation based on pseudocode here:
+	// https://en.wikipedia.org/wiki/Elliptic_curve_point_multiplication#Montgomery_ladder
+	var R0 EllipticCurvePoint
+	var R1 EllipticCurvePoint
+
+	R0.X = nil
+	R0.Y = nil
+	R1.X = new(big.Int).Set(P.X)
+	R1.Y = new(big.Int).Set(P.Y)
+
+	for i := c.N.BitLen() - 1; i >= 0; i-- {
+		if k.Bit(i) == 0 {
+			R1 = c.Add(R0, R1)
+			R0 = c.Add(R0, R0)
+		} else {
+			R0 = c.Add(R0, R1)
+			R1 = c.Add(R1, R1)
+		}
+	}
+	return R0
+}
+
+// ScalarBaseMult computes Q = k * G on EllipticCurve ec.
+func (c *EllipticCurve) ScalarBaseMult(k *big.Int) (Q EllipticCurvePoint) {
+	return c.ScalarMult(k, c.G)
+}
+
+// Decompress decompresses coordinate x and ylsb (y's least significant bit) into a EllipticCurvePoint P on EllipticCurve ec.
+func (c *EllipticCurve) Decompress(x *big.Int, ylsb uint) (P EllipticCurvePoint, err error) {
+	/* y**2 = x**3 + a*x + b  % p */
+	rhs := addMod(
+		addMod(
+			expMod(x, big.NewInt(3), c.P),
+			mulMod(c.A, x, c.P),
+			c.P),
+		c.B, c.P)
+
+	y := sqrtMod(rhs, c.P)
+	if y.Bit(0) != (ylsb & 0x1) {
+		y = subMod(big.NewInt(0), y, c.P)
+	}
+
+	P.X = x
+	P.Y = y
+
+	if !c.IsOnCurve(P) {
+		return P, errors.New("compressed (x, ylsb) not on curve")
+	}
+
+	return P, nil
+}
--- a/pkg/crypto/modular_arithmetic.go
+++ b/pkg/crypto/modular_arithmetic.go
@ -0,0 +1,61 @@
+package crypto
+
+import "math/big"
+
+// addMod computes z = (x + y) % p.
+func addMod(x *big.Int, y *big.Int, p *big.Int) (z *big.Int) {
+	z = new(big.Int).Add(x, y)
+	z.Mod(z, p)
+	return z
+}
+
+// subMod computes z = (x - y) % p.
+func subMod(x *big.Int, y *big.Int, p *big.Int) (z *big.Int) {
+	z = new(big.Int).Sub(x, y)
+	z.Mod(z, p)
+	return z
+}
+
+// mulMod computes z = (x * y) % p.
+func mulMod(x *big.Int, y *big.Int, p *big.Int) (z *big.Int) {
+	n := new(big.Int).Set(x)
+	z = big.NewInt(0)
+
+	for i := 0; i < y.BitLen(); i++ {
+		if y.Bit(i) == 1 {
+			z = addMod(z, n, p)
+		}
+		n = addMod(n, n, p)
+	}
+
+	return z
+}
+
+// invMod computes z = (1/x) % p.
+func invMod(x *big.Int, p *big.Int) (z *big.Int) {
+	z = new(big.Int).ModInverse(x, p)
+	return z
+}
+
+// expMod computes z = (x^e) % p.
+func expMod(x *big.Int, y *big.Int, p *big.Int) (z *big.Int) {
+	z = new(big.Int).Exp(x, y, p)
+	return z
+}
+
+// sqrtMod computes z = sqrt(x) % p.
+func sqrtMod(x *big.Int, p *big.Int) (z *big.Int) {
+	/* assert that p % 4 == 3 */
+	if new(big.Int).Mod(p, big.NewInt(4)).Cmp(big.NewInt(3)) != 0 {
+		panic("p is not equal to 3 mod 4!")
+	}
+
+	/* z = sqrt(x) % p = x^((p+1)/4) % p */
+
+	/* e = (p+1)/4 */
+	e := new(big.Int).Add(p, big.NewInt(1))
+	e = e.Rsh(e, 2)
+
+	z = expMod(x, e, p)
+	return z
+}
--- a/pkg/network/server.go
+++ b/pkg/network/server.go
@ -110,7 +110,7 @@ func NewServer(net NetMode) *Server {
 	}

 	// For now I will hard code a genesis block of the docker privnet container.
-	startHash, _ := util.Uint256DecodeFromString("996e37358dc369912041f966f8c5d8d3a8255ba5dcbd3447f8a82b55db869099")
+	startHash, _ := util.Uint256DecodeString("996e37358dc369912041f966f8c5d8d3a8255ba5dcbd3447f8a82b55db869099")

 	s := &Server{
 		id:          util.RandUint32(1111111, 9999999),
--- a/pkg/smartcontract/contract.go
+++ b/pkg/smartcontract/contract.go
@ -0,0 +1,5 @@
+package smartcontract
+
+// Contract represents a NEO smartcontract.
+type Contract struct {
+}
--- a/pkg/util/array.go
+++ b/pkg/util/array.go
@ -0,0 +1,14 @@
+package util
+
+// ArrayReverse return a reversed version of the given byte slice.
+func ArrayReverse(b []byte) []byte {
+	// Protect from big.Ints that have 1 len bytes.
+	if len(b) < 2 {
+		return b
+	}
+	dest := make([]byte, len(b))
+	for i, j := 0, len(b)-1; i < j; i, j = i+1, j-1 {
+		dest[i], dest[j] = b[j], b[i]
+	}
+	return dest
+}
--- a/pkg/util/array_test.go
+++ b/pkg/util/array_test.go
@ -0,0 +1,25 @@
+package util
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestArrayReverse(t *testing.T) {
+	arr := []byte{0x01, 0x02, 0x03, 0x04}
+	have := ArrayReverse(arr)
+	want := []byte{0x04, 0x03, 0x02, 0x01}
+	if bytes.Compare(have, want) != 0 {
+		t.Fatalf("expected %v got %v", want, have)
+	}
+}
+
+// This tests a bug that occured with arrays of size 1
+func TestArrayReverseLen2(t *testing.T) {
+	arr := []byte{0x01}
+	have := ArrayReverse(arr)
+	want := []byte{0x01}
+	if bytes.Compare(have, want) != 0 {
+		t.Fatalf("expected %v got %v", want, have)
+	}
+}
--- a/pkg/util/uint160.go
+++ b/pkg/util/uint160.go
@ -2,6 +2,7 @@ package util

 import (
 	"encoding/hex"
+	"fmt"
 )

 const uint160Size = 20
@ -9,8 +10,31 @@ const uint160Size = 20
 // Uint160 is a 20 byte long unsigned integer.
 type Uint160 [uint160Size]uint8

-// ToSlice returns a byte slice of u.
-func (u Uint160) ToSlice() []byte {
+// Uint160DecodeString attempts to decode the given string into an Uint160.
+func Uint160DecodeString(s string) (u Uint160, err error) {
+	if len(s) != uint160Size*2 {
+		return u, fmt.Errorf("expected string size of %d got %d", uint160Size*2, len(s))
+	}
+	b, err := hex.DecodeString(s)
+	if err != nil {
+		return u, err
+	}
+	return Uint160DecodeBytes(b)
+}
+
+// Uint160DecodeBytes attempts to decode the given bytes into an Uint160.
+func Uint160DecodeBytes(b []byte) (u Uint160, err error) {
+	if len(b) != uint160Size {
+		return u, fmt.Errorf("expected byte size of %d got %d", uint160Size, len(b))
+	}
+	for i := 0; i < uint160Size; i++ {
+		u[i] = b[i]
+	}
+	return
+}
+
+// Bytes returns the byte slice representation of u.
+func (u Uint160) Bytes() []byte {
 	b := make([]byte, uint160Size)
 	for i := 0; i < uint160Size; i++ {
 		b[i] = byte(u[i])
@ -20,10 +44,15 @@ func (u Uint160) ToSlice() []byte {

 // String implements the stringer interface.
 func (u Uint160) String() string {
-	return hex.EncodeToString(u.ToSlice())
+	return hex.EncodeToString(u.Bytes())
 }

 // Equals returns true if both Uint256 values are the same.
 func (u Uint160) Equals(other Uint160) bool {
-	return u.String() == other.String()
+	for i := 0; i < uint160Size; i++ {
+		if u[i] != other[i] {
+			return false
+		}
+	}
+	return true
 }
--- a/pkg/util/uint160_test.go
+++ b/pkg/util/uint160_test.go
@ -0,0 +1 @@
+package util
--- a/pkg/util/uint256.go
+++ b/pkg/util/uint256.go
@ -10,56 +10,32 @@ const uint256Size = 32
 // Uint256 is a 32 byte long unsigned integer.
 type Uint256 [uint256Size]uint8

-// Uint256DecodeFromString returns an Uint256 from a (hex) string.
-func Uint256DecodeFromString(s string) (Uint256, error) {
-	var val Uint256
-
+// Uint256DecodeString attempts to decode the given string into an Uint256.
+func Uint256DecodeString(s string) (u Uint256, err error) {
 	if len(s) != uint256Size*2 {
-		return val, fmt.Errorf("expected string size of %d got %d", uint256Size*2, len(s))
+		return u, fmt.Errorf("expected string size of %d got %d", uint256Size*2, len(s))
 	}
-
 	b, err := hex.DecodeString(s)
 	if err != nil {
-		return val, err
+		return u, err
 	}
-
-	b = ToArrayReverse(b)
-
-	return Uint256DecodeFromBytes(b)
+	return Uint256DecodeBytes(b)
 }

-// Uint256DecodeFromBytes return an Uint256 from a byte slice.
-func Uint256DecodeFromBytes(b []byte) (Uint256, error) {
-	var val Uint256
-
+// Uint256DecodeBytes attempts to decode the given string into an Uint256.
+func Uint256DecodeBytes(b []byte) (u Uint256, err error) {
+	b = ArrayReverse(b)
 	if len(b) != uint256Size {
-		return val, fmt.Errorf("expected []byte of size %d got %d", uint256Size, len(b))
+		return u, fmt.Errorf("expected []byte of size %d got %d", uint256Size, len(b))
 	}
-
 	for i := 0; i < uint256Size; i++ {
-		val[i] = b[i]
+		u[i] = b[i]
 	}
-
-	return val, nil
+	return u, nil
 }

-// ToArrayReverse return a reversed version of the given byte slice.
-func ToArrayReverse(b []byte) []byte {
-	// Protect from big.Ints that have 1 len bytes.
-	if len(b) < 2 {
-		return b
-	}
-
-	dest := make([]byte, len(b))
-	for i, j := 0, len(b)-1; i < j; i, j = i+1, j-1 {
-		dest[i], dest[j] = b[j], b[i]
-	}
-
-	return dest
-}
-
-// ToSlice returns a byte slice of u.
-func (u Uint256) ToSlice() []byte {
+// ToSlice returns a byte slice representation of u.
+func (u Uint256) Bytes() []byte {
 	b := make([]byte, uint256Size)
 	for i := 0; i < uint256Size; i++ {
 		b[i] = byte(u[i])
@ -67,13 +43,9 @@ func (u Uint256) ToSlice() []byte {
 	return b
 }

-// ToSliceReverse returns a reversed byte slice of u.
-func (u Uint256) ToSliceReverse() []byte {
-	b := make([]byte, uint256Size)
-	for i, j := 0, uint256Size-1; i < j; i, j = i+1, j-1 {
-		b[i], b[j] = byte(u[j]), byte(u[i])
-	}
-	return b
+// BytesReverse return a reversed byte representation of u.
+func (u Uint256) BytesReverse() []byte {
+	return ArrayReverse(u.Bytes())
 }

 // Equals returns true if both Uint256 values are the same.
@ -83,5 +55,5 @@ func (u Uint256) Equals(other Uint256) bool {

 // String implements the stringer interface.
 func (u Uint256) String() string {
-	return hex.EncodeToString(u.ToSliceReverse())
+	return hex.EncodeToString(ArrayReverse(u.Bytes()))
 }
--- a/pkg/util/uint256_test.go
+++ b/pkg/util/uint256_test.go
@ -1,25 +1,50 @@
 package util

 import (
-	"bytes"
+	"encoding/hex"
 	"testing"
 )

-func TestToArrayReverse(t *testing.T) {
-	arr := []byte{0x01, 0x02, 0x03, 0x04}
-	have := ToArrayReverse(arr)
-	want := []byte{0x04, 0x03, 0x02, 0x01}
-	if bytes.Compare(have, want) != 0 {
-		t.Fatalf("expected %v got %v", want, have)
+func TestUint256DecodeString(t *testing.T) {
+	hexStr := "f037308fa0ab18155bccfc08485468c112409ea5064595699e98c545f245f32d"
+	val, err := Uint256DecodeString(hexStr)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Log(val)
+}
+
+func TestUint256DecodeBytes(t *testing.T) {
+	hexStr := "f037308fa0ab18155bccfc08485468c112409ea5064595699e98c545f245f32d"
+	b, err := hex.DecodeString(hexStr)
+	if err != nil {
+		t.Fatal(err)
+	}
+	val, err := Uint256DecodeBytes(b)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if val.String() != hexStr {
+		t.Fatalf("expected %s and %s to be equal", val, hexStr)
 	}
 }

-// This tests a bug that occured with arrays of size 1
-func TestToArrayReverseLen2(t *testing.T) {
-	arr := []byte{0x01}
-	have := ToArrayReverse(arr)
-	want := []byte{0x01}
-	if bytes.Compare(have, want) != 0 {
-		t.Fatalf("expected %v got %v", want, have)
+func TestUInt256Equals(t *testing.T) {
+	a := "f037308fa0ab18155bccfc08485468c112409ea5064595699e98c545f245f32d"
+	b := "e287c5b29a1b66092be6803c59c765308ac20287e1b4977fd399da5fc8f66ab5"
+
+	ua, err := Uint256DecodeString(a)
+	if err != nil {
+		t.Fatal(err)
+	}
+	ub, err := Uint256DecodeString(b)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if ua.Equals(ub) {
+		t.Fatalf("%s and %s cannot be equal", ua, ub)
+	}
+	if !ua.Equals(ua) {
+		t.Fatalf("%s and %s must be equal", ua, ua)
 	}
 }
--- a/pkg/vm/compiler/emit.go
+++ b/pkg/vm/compiler/emit.go
@ -43,7 +43,7 @@ func emitInt(w *bytes.Buffer, i int64) error {
 	}

 	bInt := big.NewInt(i)
-	val := util.ToArrayReverse(bInt.Bytes())
+	val := util.ArrayReverse(bInt.Bytes())
 	return emitBytes(w, val)
 }

--- a/pkg/wallet/account.go
+++ b/pkg/wallet/account.go
@ -0,0 +1,113 @@
+package wallet
+
+import "github.com/anthdm/neo-go/pkg/util"
+
+// Account represents a NEO account. It holds the private and public key
+// along with some metadata.
+type Account struct {
+	// NEO private key.
+	privateKey *PrivateKey
+
+	// NEO public key.
+	publicKey []byte
+
+	// Account import file.
+	wif string
+
+	// NEO public addresss.
+	Address string `json:"address"`
+
+	// Encrypted WIF of the account also known as the key.
+	EncryptedWIF string `json:"key"`
+
+	// Label is a label the user had made for this account.
+	Label string `json:"label"`
+
+	// contract is a Contract object which describes the details of the contract.
+	// This field can be null (for watch-only address).
+	Contract *Contract `json:"contract"`
+
+	// Indicates whether the account is locked by the user.
+	// the client shouldn't spend the funds in a locked account.
+	Locked bool `json:"lock"`
+
+	// Indicates whether the account is the default change account.
+	Default bool `json:"isDefault"`
+}
+
+// Contract represents a subset of the smartcontract to embedd in the
+// Account so it's NEP-6 compliant.
+type Contract struct {
+	// Script hash of the contract deployed on the blockchain.
+	Script util.Uint160 `json:"script"`
+
+	// A list of parameters used deploying this contract.
+	Parameters []interface{} `json:"parameters"`
+
+	// Indicates whether the contract has been deployed to the blockchain.
+	Deployed bool `json:"deployed"`
+}
+
+// NewAccount creates a new Account with a random generated PrivateKey.
+func NewAccount() (*Account, error) {
+	priv, err := NewPrivateKey()
+	if err != nil {
+		return nil, err
+	}
+	return newAccountFromPrivateKey(priv)
+}
+
+// DecryptAccount decrypt the encryptedWIF with the given passphrase and
+// return the decrypted Account.
+func DecryptAccount(encryptedWIF, passphrase string) (*Account, error) {
+	wif, err := NEP2Decrypt(encryptedWIF, passphrase)
+	if err != nil {
+		return nil, err
+	}
+	return NewAccountFromWIF(wif)
+}
+
+// Encrypt encrypts the wallet's PrivateKey with the given passphrase
+// under the NEP-2 standard.
+func (a *Account) Encrypt(passphrase string) error {
+	wif, err := NEP2Encrypt(a.privateKey, passphrase)
+	if err != nil {
+		return err
+	}
+	a.EncryptedWIF = wif
+	return nil
+}
+
+// NewAccountFromWIF creates a new Account from the given WIF.
+func NewAccountFromWIF(wif string) (*Account, error) {
+	privKey, err := NewPrivateKeyFromWIF(wif)
+	if err != nil {
+		return nil, err
+	}
+	return newAccountFromPrivateKey(privKey)
+}
+
+// newAccountFromPrivateKey created a wallet from the given PrivateKey.
+func newAccountFromPrivateKey(p *PrivateKey) (*Account, error) {
+	pubKey, err := p.PublicKey()
+	if err != nil {
+		return nil, err
+	}
+	pubAddr, err := p.Address()
+	if err != nil {
+		return nil, err
+	}
+	wif, err := p.WIF()
+	if err != nil {
+		return nil, err
+	}
+
+	a := &Account{
+		publicKey:  pubKey,
+		privateKey: p,
+		Address:    pubAddr,
+		wif:        wif,
+	}
+
+	return a, nil
+}
--- a/pkg/wallet/account_test.go
+++ b/pkg/wallet/account_test.go
@ -0,0 +1,51 @@
+package wallet
+
+import (
+	"encoding/hex"
+	"testing"
+)
+
+func TestNewAccount(t *testing.T) {
+	for _, testCase := range testKeyCases {
+		acc, err := NewAccountFromWIF(testCase.wif)
+		if err != nil {
+			t.Fatal(err)
+		}
+		compareFields(t, testCase, acc)
+	}
+}
+
+func TestDecryptAccount(t *testing.T) {
+	for _, testCase := range testKeyCases {
+		acc, err := DecryptAccount(testCase.encryptedWif, testCase.passphrase)
+		if err != nil {
+			t.Fatal(err)
+		}
+		compareFields(t, testCase, acc)
+	}
+}
+
+func TestNewFromWif(t *testing.T) {
+	for _, testCase := range testKeyCases {
+		acc, err := NewAccountFromWIF(testCase.wif)
+		if err != nil {
+			t.Fatal(err)
+		}
+		compareFields(t, testCase, acc)
+	}
+}
+
+func compareFields(t *testing.T, tk testKey, acc *Account) {
+	if want, have := tk.address, acc.Address; want != have {
+		t.Fatalf("expected %s got %s", want, have)
+	}
+	if want, have := tk.wif, acc.wif; want != have {
+		t.Fatalf("expected %s got %s", want, have)
+	}
+	if want, have := tk.publicKey, hex.EncodeToString(acc.publicKey); want != have {
+		t.Fatalf("expected %s got %s", want, have)
+	}
+	if want, have := tk.privateKey, acc.privateKey.String(); want != have {
+		t.Fatalf("expected %s got %s", want, have)
+	}
+}
--- a/pkg/wallet/nep2.go
+++ b/pkg/wallet/nep2.go
@ -0,0 +1,165 @@
+package wallet
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"errors"
+	"fmt"
+
+	"github.com/CityOfZion/neo-go/pkg/crypto"
+	"golang.org/x/crypto/scrypt"
+	"golang.org/x/text/unicode/norm"
+)
+
+// NEP-2 standard implementation for encrypting and decrypting wallets.
+
+// NEP-2 specified parameters used for cryptography.
+const (
+	n       = 16384
+	r       = 8
+	p       = 8
+	keyLen  = 64
+	nepFlag = 0xe0
+)
+
+var nepHeader = []byte{0x01, 0x42}
+
+type scryptParams struct {
+	N int `json:"n"`
+	R int `json:"r"`
+	P int `json:"p"`
+}
+
+func newScryptParams() scryptParams {
+	return scryptParams{
+		N: n,
+		R: r,
+		P: p,
+	}
+}
+
+// NEP2Encrypt encrypts a the PrivateKey using a given passphrase
+// under the NEP-2 standard.
+func NEP2Encrypt(priv *PrivateKey, passphrase string) (s string, err error) {
+	address, err := priv.Address()
+	if err != nil {
+		return s, err
+	}
+
+	addrHash := hashAddress(address)[0:4]
+	// Normalize the passphrase according to the NFC standard.
+	phraseNorm := norm.NFC.Bytes([]byte(passphrase))
+	derivedKey, err := scrypt.Key(phraseNorm, addrHash, n, r, p, keyLen)
+	if err != nil {
+		return s, err
+	}
+
+	derivedKey1 := derivedKey[:32]
+	derivedKey2 := derivedKey[32:]
+	xr := xor(priv.Bytes(), derivedKey1)
+
+	encrypted, err := crypto.AESEncrypt(derivedKey2, xr)
+	if err != nil {
+		return s, err
+	}
+
+	buf := new(bytes.Buffer)
+	buf.Write(nepHeader)
+	buf.WriteByte(nepFlag)
+	buf.Write(addrHash)
+	buf.Write(encrypted)
+
+	if buf.Len() != 39 {
+		return s, fmt.Errorf("invalid buffer length: expecting 39 bytes got %d", buf.Len())
+	}
+
+	return crypto.Base58CheckEncode(buf.Bytes()), nil
+}
+
+// NEP2Decrypt decrypts an encrypted key using a given passphrase
+// under the NEP-2 standard.
+func NEP2Decrypt(key, passphrase string) (s string, err error) {
+	b, err := crypto.Base58CheckDecode(key)
+	if err != nil {
+		return s, nil
+	}
+	if err := validateNEP2Format(b); err != nil {
+		return s, err
+	}
+
+	addrHash := b[3:7]
+	// Normalize the passphrase according to the NFC standard.
+	phraseNorm := norm.NFC.Bytes([]byte(passphrase))
+	derivedKey, err := scrypt.Key(phraseNorm, addrHash, n, r, p, keyLen)
+	if err != nil {
+		return s, err
+	}
+
+	derivedKey1 := derivedKey[:32]
+	derivedKey2 := derivedKey[32:]
+	encryptedBytes := b[7:]
+
+	decrypted, err := crypto.AESDecrypt(encryptedBytes, derivedKey2)
+	if err != nil {
+		return s, err
+	}
+
+	privBytes := xor(decrypted, derivedKey1)
+
+	// Rebuild the private key.
+	privKey, err := NewPrivateKeyFromBytes(privBytes)
+	if err != nil {
+		return s, err
+	}
+
+	if !compareAddressHash(privKey, addrHash) {
+		return s, errors.New("password mismatch")
+	}
+
+	return privKey.WIF()
+}
+
+func compareAddressHash(priv *PrivateKey, hash []byte) bool {
+	address, err := priv.Address()
+	if err != nil {
+		return false
+	}
+	addrHash := hashAddress(address)[0:4]
+	return bytes.Compare(addrHash, hash) == 0
+}
+
+func validateNEP2Format(b []byte) error {
+	if len(b) != 39 {
+		return fmt.Errorf("invalid length: expecting 39 got %d", len(b))
+	}
+	if b[0] != 0x01 {
+		return fmt.Errorf("invalid byte sequence: expecting 0x01 got 0x%02x", b[0])
+	}
+	if b[1] != 0x42 {
+		return fmt.Errorf("invalid byte sequence: expecting 0x42 got 0x%02x", b[1])
+	}
+	if b[2] != 0xe0 {
+		return fmt.Errorf("invalid byte sequence: expecting 0xe0 got 0x%02x", b[2])
+	}
+	return nil
+}
+
+func xor(a, b []byte) []byte {
+	if len(a) != len(b) {
+		panic("cannot XOR non equal length arrays")
+	}
+	dst := make([]byte, len(a))
+	for i := 0; i < len(dst); i++ {
+		dst[i] = a[i] ^ b[i]
+	}
+	return dst
+}
+
+func hashAddress(addr string) []byte {
+	sha := sha256.New()
+	sha.Write([]byte(addr))
+	hash := sha.Sum(nil)
+	sha.Reset()
+	sha.Write(hash)
+	return sha.Sum(nil)
+}
--- a/pkg/wallet/private_key.go
+++ b/pkg/wallet/private_key.go
@ -0,0 +1,193 @@
+package wallet
+
+import (
+	"bytes"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io"
+	"math/big"
+
+	"github.com/CityOfZion/neo-go/pkg/crypto"
+	"github.com/anthdm/rfc6979"
+	"golang.org/x/crypto/ripemd160"
+)
+
+// PrivateKey represents a NEO private key.
+type PrivateKey struct {
+	b []byte
+}
+
+func NewPrivateKey() (*PrivateKey, error) {
+	c := crypto.NewEllipticCurve()
+	b := make([]byte, c.N.BitLen()/8+8)
+	if _, err := io.ReadFull(rand.Reader, b); err != nil {
+		return nil, err
+	}
+
+	d := new(big.Int).SetBytes(b)
+	d.Mod(d, new(big.Int).Sub(c.N, big.NewInt(1)))
+	d.Add(d, big.NewInt(1))
+
+	p := &PrivateKey{b: d.Bytes()}
+	return p, nil
+}
+
+// NewPrivateKeyFromHex returns a PrivateKey created from the
+// given hex string.
+func NewPrivateKeyFromHex(str string) (*PrivateKey, error) {
+	b, err := hex.DecodeString(str)
+	if err != nil {
+		return nil, err
+	}
+	return NewPrivateKeyFromBytes(b)
+}
+
+// NewPrivateKeyFromBytes returns a NEO PrivateKey from the given byte slice.
+func NewPrivateKeyFromBytes(b []byte) (*PrivateKey, error) {
+	if len(b) != 32 {
+		return nil, fmt.Errorf(
+			"invalid byte length: expected %d bytes got %d", 32, len(b),
+		)
+	}
+	return &PrivateKey{b}, nil
+}
+
+// PublicKey derives the public key from the private key.
+func (p *PrivateKey) PublicKey() ([]byte, error) {
+	var (
+		c = crypto.NewEllipticCurve()
+		q = new(big.Int).SetBytes(p.b)
+	)
+
+	point := c.ScalarBaseMult(q)
+	if !c.IsOnCurve(point) {
+		return nil, errors.New("failed to derive public key using elliptic curve")
+	}
+
+	bx := point.X.Bytes()
+	padded := append(
+		bytes.Repeat(
+			[]byte{0x00},
+			32-len(bx),
+		),
+		bx...,
+	)
+
+	prefix := []byte{0x03}
+	if point.Y.Bit(0) == 0 {
+		prefix = []byte{0x02}
+	}
+	b := append(prefix, padded...)
+
+	return b, nil
+}
+
+// NewPrivateKeyFromWIF returns a NEO PrivateKey from the given
+// WIF (wallet import format).
+func NewPrivateKeyFromWIF(wif string) (*PrivateKey, error) {
+	w, err := WIFDecode(wif, WIFVersion)
+	if err != nil {
+		return nil, err
+	}
+	return w.PrivateKey, nil
+}
+
+// WIF returns the (wallet import format) of the PrivateKey.
+// Good documentation about this process can be found here:
+// https://en.bitcoin.it/wiki/Wallet_import_format
+func (p *PrivateKey) WIF() (string, error) {
+	return WIFEncode(p.b, WIFVersion, true)
+}
+
+// Address derives the public NEO address that is coupled with the private key, and
+// returns it as a string.
+func (p *PrivateKey) Address() (string, error) {
+	b, err := p.Signature()
+	if err != nil {
+		return "", err
+	}
+
+	b = append([]byte{0x17}, b...)
+
+	sha := sha256.New()
+	sha.Write(b)
+	hash := sha.Sum(nil)
+
+	sha.Reset()
+	sha.Write(hash)
+	hash = sha.Sum(nil)
+
+	b = append(b, hash[0:4]...)
+
+	address := crypto.Base58Encode(b)
+
+	return address, nil
+}
+
+// Signature creates the signature using the private key.
+func (p *PrivateKey) Signature() ([]byte, error) {
+	b, err := p.PublicKey()
+	if err != nil {
+		return nil, err
+	}
+
+	b = append([]byte{0x21}, b...)
+	b = append(b, 0xAC)
+
+	sha := sha256.New()
+	sha.Write(b)
+	hash := sha.Sum(nil)
+
+	ripemd := ripemd160.New()
+	ripemd.Reset()
+	ripemd.Write(hash)
+	hash = ripemd.Sum(nil)
+
+	return hash, nil
+}
+
+// Sign signs arbitrary length data using the private key.
+func (p *PrivateKey) Sign(data []byte) ([]byte, error) {
+	var (
+		privateKey = p.ecdsa()
+		digest     = sha256.Sum256(data)
+	)
+
+	r, s, err := rfc6979.SignECDSA(privateKey, digest[:], sha256.New)
+	if err != nil {
+		return nil, err
+	}
+
+	params := privateKey.Curve.Params()
+	curveOrderByteSize := params.P.BitLen() / 8
+	rBytes, sBytes := r.Bytes(), s.Bytes()
+	signature := make([]byte, curveOrderByteSize*2)
+	copy(signature[curveOrderByteSize-len(rBytes):], rBytes)
+	copy(signature[curveOrderByteSize*2-len(sBytes):], sBytes)
+
+	return signature, nil
+}
+
+// ecsda converts the key to a usable ecsda.PrivateKey for signing data.
+func (p *PrivateKey) ecdsa() *ecdsa.PrivateKey {
+	priv := new(ecdsa.PrivateKey)
+	priv.PublicKey.Curve = elliptic.P256()
+	priv.D = new(big.Int).SetBytes(p.b)
+	priv.PublicKey.X, priv.PublicKey.Y = priv.PublicKey.Curve.ScalarBaseMult(p.b)
+	return priv
+}
+
+// String implements the stringer interface.
+func (p *PrivateKey) String() string {
+	return hex.EncodeToString(p.b)
+}
+
+// Bytes returns the underlying bytes of the PrivateKey.
+func (p *PrivateKey) Bytes() []byte {
+	return p.b
+}
--- a/pkg/wallet/private_key_test.go
+++ b/pkg/wallet/private_key_test.go
@ -0,0 +1,74 @@
+package wallet
+
+import "testing"
+
+type testKey struct {
+	address,
+	privateKey,
+	publicKey,
+	wif,
+	passphrase,
+	encryptedWif string
+}
+
+var testKeyCases = []testKey{
+	{
+		address:      "ALq7AWrhAueN6mJNqk6FHJjnsEoPRytLdW",
+		privateKey:   "7d128a6d096f0c14c3a25a2b0c41cf79661bfcb4a8cc95aaaea28bde4d732344",
+		publicKey:    "02028a99826edc0c97d18e22b6932373d908d323aa7f92656a77ec26e8861699ef",
+		wif:          "L1QqQJnpBwbsPGAuutuzPTac8piqvbR1HRjrY5qHup48TBCBFe4g",
+		passphrase:   "city of zion",
+		encryptedWif: "6PYLHmDf6AjF4AsVtosmxHuPYeuyJL3SLuw7J1U8i7HxKAnYNsp61HYRfF",
+	},
+	{
+		address:      "ALfnhLg7rUyL6Jr98bzzoxz5J7m64fbR4s",
+		privateKey:   "9ab7e154840daca3a2efadaf0df93cd3a5b51768c632f5433f86909d9b994a69",
+		publicKey:    "031d8e1630ce640966967bc6d95223d21f44304133003140c3b52004dc981349c9",
+		wif:          "L2QTooFoDFyRFTxmtiVHt5CfsXfVnexdbENGDkkrrgTTryiLsPMG",
+		passphrase:   "我的密码",
+		encryptedWif: "6PYWVp3xfgvnuNKP7ZavSViYvvim2zuzx9Q33vuWZr8aURiKeJ6Zm7BfPQ",
+	},
+	{
+		address:      "AVf4UGKevVrMR1j3UkPsuoYKSC4ocoAkKx",
+		privateKey:   "3edee7036b8fd9cef91de47386b191dd76db2888a553e7736bb02808932a915b",
+		publicKey:    "02232ce8d2e2063dce0451131851d47421bfc4fc1da4db116fca5302c0756462fa",
+		wif:          "KyKvWLZsNwBJx5j9nurHYRwhYfdQUu9tTEDsLCUHDbYBL8cHxMiG",
+		passphrase:   "MyL33tP@33w0rd",
+		encryptedWif: "6PYNoc1EG5J38MTqGN9Anphfdd6UwbS4cpFCzHhrkSKBBbV1qkbJJZQnkn",
+	},
+}
+
+func TestPrivateKey(t *testing.T) {
+	for _, testCase := range testKeyCases {
+		privKey, err := NewPrivateKeyFromHex(testCase.privateKey)
+		if err != nil {
+			t.Fatal(err)
+		}
+		address, err := privKey.Address()
+		if err != nil {
+			t.Fatal(err)
+		}
+		if want, have := testCase.address, address; want != have {
+			t.Fatalf("expected %s got %s", want, have)
+		}
+		wif, err := privKey.WIF()
+		if err != nil {
+			t.Fatal(err)
+		}
+		if want, have := testCase.wif, wif; want != have {
+			t.Fatalf("expected %s got %s", want, have)
+		}
+	}
+}
+
+func TestPrivateKeyFromWIF(t *testing.T) {
+	for _, testCase := range testKeyCases {
+		key, err := NewPrivateKeyFromWIF(testCase.wif)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if want, have := testCase.privateKey, key.String(); want != have {
+			t.Fatalf("expected %s got %s", want, have)
+		}
+	}
+}
--- a/pkg/wallet/public_key.go
+++ b/pkg/wallet/public_key.go
@ -0,0 +1,64 @@
+package wallet
+
+//// PublicKey represent a NEO public key.
+//type PublicKey struct {
+//	crypto.EllipticCurvePoint
+//}
+//
+//// Bytes returns a byteslice representation of the PublicKey.
+//func (p *PublicKey) Bytes() []byte {
+//	b := p.X.Bytes()
+//	padding := append(
+//		bytes.Repeat(
+//			[]byte{0x00},
+//			32-len(b),
+//		),
+//		b...,
+//	)
+//
+//	prefix := []byte{0x03}
+//	if p.Y.Bit(0) == 0 {
+//		prefix = []byte{0x02}
+//	}
+//
+//	return append(prefix, padding...)
+//}
+//
+//// Signature creates the signature of the PublicKey.
+//func (p *PublicKey) Signature() []byte {
+//	b := p.Bytes()
+//
+//	b = append([]byte{0x21}, b...)
+//	b = append(b, 0xAC)
+//
+//	sha256H := sha256.New()
+//	sha256H.Write(b)
+//	hash := sha256H.Sum(nil)
+//
+//	ripemd160H := ripemd160.New()
+//	ripemd160H.Write(hash)
+//	return ripemd160H.Sum(nil)
+//}
+//
+//// PublicAddress derives the public NEO address that is coupled with the private key,
+//// and returns it as a string.
+//func (p *PublicKey) PublicAddress() string {
+//	var (
+//		b        = p.Signature()
+//		ver byte = 0x17
+//	)
+//
+//	b = append([]byte{ver}, b...)
+//
+//	sha256H := sha256.New()
+//	sha256H.Write(b)
+//	hash := sha256H.Sum(nil)
+//
+//	sha256H.Reset()
+//	sha256H.Write(hash)
+//	hash = sha256H.Sum(nil)
+//
+//	b = append(b, hash[0:4]...)
+//
+//	return crypto.Base58Encode(b)
+//}
--- a/pkg/wallet/transfer_output.go
+++ b/pkg/wallet/transfer_output.go
@ -0,0 +1,21 @@
+package wallet
+
+import (
+	"math/big"
+
+	"github.com/anthdm/neo-go/pkg/util"
+)
+
+// TransferOutput respresents the output of a transaction.
+type TransferOutput struct {
+	// The asset identifier. This should be of type Uint256.
+	// NEO governing token: c56f33fc6ecfcd0c225c4ab356fee59390af8560be0e930faebe74a6daff7c9b
+	// NEO gas: 			602c79718b16e442de58778e148d0b1084e3b2dffd5de6b7b16cee7969282de7
+	AssetID util.Uint256
+
+	// Value of the transfer
+	Value *big.Int
+
+	// ScriptHash of the transfer.
+	ScriptHash util.Uint160
+}
--- a/pkg/wallet/wallet.go
+++ b/pkg/wallet/wallet.go
@ -0,0 +1,117 @@
+package wallet
+
+import (
+	"encoding/json"
+	"io"
+	"os"
+)
+
+const (
+	// The current version of neo-go wallet implementations.
+	walletVersion = "1.0"
+)
+
+// Wallet respresents a NEO (NEP-2, NEP-6) compliant wallet.
+type Wallet struct {
+	// Version of the wallet, used for later upgrades.
+	Version string `json:"version"`
+
+	// A list of accounts which decribes the details of each account
+	// in the wallet.
+	Accounts []*Account `json:"accounts"`
+
+	Scrypt scryptParams `json:"scrypt"`
+
+	// Extra metadata can be used for storing abritrary data.
+	// This field can be empty.
+	Extra interface{} `json:"extra"`
+
+	// Path where the wallet file is located..
+	path string
+
+	// ReadWriter for reading and writing wallet data.
+	rw io.ReadWriter
+}
+
+// NewWallet creates a new NEO wallet at the given location.
+func NewWallet(location string) (*Wallet, error) {
+	file, err := os.Create(location)
+	if err != nil {
+		return nil, err
+	}
+	return newWallet(file), nil
+}
+
+// NewWalletFromFile creates a Wallet from the given wallet file path
+func NewWalletFromFile(path string) (*Wallet, error) {
+	file, err := os.OpenFile(path, os.O_RDWR, os.ModeAppend)
+	if err != nil {
+		return nil, err
+	}
+	wall := &Wallet{
+		rw:   file,
+		path: file.Name(),
+	}
+	if err := json.NewDecoder(file).Decode(wall); err != nil {
+		return nil, err
+	}
+	return wall, nil
+}
+
+func newWallet(rw io.ReadWriter) *Wallet {
+	var path string
+	if f, ok := rw.(*os.File); ok {
+		path = f.Name()
+	}
+	return &Wallet{
+		Version:  walletVersion,
+		Accounts: []*Account{},
+		Scrypt:   newScryptParams(),
+		rw:       rw,
+		path:     path,
+	}
+}
+
+// CreatAccount generates a new account for the end user and ecrypts
+// the private key with the given passphrase.
+func (w *Wallet) CreateAccount(name, passphrase string) error {
+	acc, err := NewAccount()
+	if err != nil {
+		return err
+	}
+	acc.Label = name
+	if err := acc.Encrypt(passphrase); err != nil {
+		return err
+	}
+	w.AddAccount(acc)
+	return w.Save()
+}
+
+// AddAccount adds an existing Account to the wallet.
+func (w *Wallet) AddAccount(acc *Account) {
+	w.Accounts = append(w.Accounts, acc)
+}
+
+// Path returns the location of the wallet on the filesystem.
+func (w *Wallet) Path() string {
+	return w.path
+}
+
+// Save saves the wallet data. It's the internal io.ReadWriter
+// that is responsible for saving the data. This can
+// be a buffer, file, etc..
+func (w *Wallet) Save() error {
+	return json.NewEncoder(w.rw).Encode(w)
+}
+
+// JSON outputs a pretty JSON representation of the wallet.
+func (w *Wallet) JSON() ([]byte, error) {
+	return json.MarshalIndent(w, " ", "	")
+}
+
+// Close closes the internal rw if its an io.ReadCloser.
+func (w *Wallet) Close() {
+	if rc, ok := w.rw.(io.ReadCloser); ok {
+		rc.Close()
+	}
+}
--- a/pkg/wallet/wallet_test.go
+++ b/pkg/wallet/wallet_test.go
@ -0,0 +1,8 @@
+package wallet
+
+import (
+	"testing"
+)
+
+func TestNewWallet(t *testing.T) {
+}
--- a/pkg/wallet/wif.go
+++ b/pkg/wallet/wif.go
@ -0,0 +1,92 @@
+package wallet
+
+import (
+	"bytes"
+	"fmt"
+
+	"github.com/CityOfZion/neo-go/pkg/crypto"
+)
+
+const (
+	// The WIF network version used to decode and encode WIF keys.
+	WIFVersion = 0x80
+)
+
+// WIF represents a wallet import format.
+type WIF struct {
+	// Version of the wallet import format. Default to 0x80.
+	Version byte
+
+	// Bool to determine if the WIF is compressed or not.
+	Compressed bool
+
+	// A reference to the PrivateKey which this WIF is created from.
+	PrivateKey *PrivateKey
+
+	// The string representation of the WIF.
+	S string
+}
+
+// WIFEncode encodes the given private key into a WIF string.
+func WIFEncode(key []byte, version byte, compressed bool) (s string, err error) {
+	if version == 0x00 {
+		version = WIFVersion
+	}
+	if len(key) != 32 {
+		return s, fmt.Errorf("invalid private key length: %d", len(key))
+	}
+
+	buf := new(bytes.Buffer)
+	buf.WriteByte(version)
+	buf.Write(key)
+	if compressed {
+		buf.WriteByte(0x01)
+	}
+
+	s = crypto.Base58CheckEncode(buf.Bytes())
+	return
+}
+
+// WIFDecode decoded the given WIF string into a WIF struct.
+func WIFDecode(wif string, version byte) (*WIF, error) {
+	b, err := crypto.Base58CheckDecode(wif)
+	if err != nil {
+		return nil, err
+	}
+
+	if version == 0x00 {
+		version = WIFVersion
+	}
+	if b[0] != version {
+		return nil, fmt.Errorf("invalid WIF version got %d, expected %d", b[0], version)
+	}
+
+	// Derive the PrivateKey.
+	privKey, err := NewPrivateKeyFromBytes(b[1:33])
+	if err != nil {
+		return nil, err
+	}
+	w := &WIF{
+		Version:    version,
+		PrivateKey: privKey,
+		S:          wif,
+	}
+
+	// This is an uncompressed WIF
+	if len(b) == 33 {
+		w.Compressed = false
+		return w, nil
+	}
+
+	if len(b) != 34 {
+		return nil, fmt.Errorf("invalid WIF length: %d expecting 34", len(b))
+	}
+
+	// Check the compression flag.
+	if b[33] != 0x01 {
+		return nil, fmt.Errorf("invalid compression flag %d expecting %d", b[34], 0x01)
+	}
+
+	w.Compressed = true
+	return w, nil
+}
--- a/pkg/wallet/wif_test.go
+++ b/pkg/wallet/wif_test.go
@ -0,0 +1,64 @@
+package wallet
+
+import (
+	"encoding/hex"
+	"testing"
+)
+
+type wifTestCase struct {
+	wif        string
+	compressed bool
+	privateKey string
+	version    byte
+}
+
+var wifTestCases = []wifTestCase{
+	{
+		wif:        "KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3qYjgd9M7rFU73sVHnoWn",
+		compressed: true,
+		privateKey: "0000000000000000000000000000000000000000000000000000000000000001",
+		version:    0x80,
+	},
+	{
+		wif:        "5HpHagT65TZzG1PH3CSu63k8DbpvD8s5ip4nEB3kEsreAnchuDf",
+		compressed: false,
+		privateKey: "0000000000000000000000000000000000000000000000000000000000000001",
+		version:    0x80,
+	},
+	{
+		wif:        "KxhEDBQyyEFymvfJD96q8stMbJMbZUb6D1PmXqBWZDU2WvbvVs9o",
+		compressed: true,
+		privateKey: "2bfe58ab6d9fd575bdc3a624e4825dd2b375d64ac033fbc46ea79dbab4f69a3e",
+		version:    0x80,
+	},
+}
+
+func TestWIFEncodeDecode(t *testing.T) {
+	for _, testCase := range wifTestCases {
+		b, err := hex.DecodeString(testCase.privateKey)
+		if err != nil {
+			t.Fatal(err)
+		}
+		wif, err := WIFEncode(b, testCase.version, testCase.compressed)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if want, have := testCase.wif, wif; want != have {
+			t.Fatalf("expected %s got %s", want, have)
+		}
+
+		WIF, err := WIFDecode(wif, testCase.version)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if want, have := testCase.privateKey, WIF.PrivateKey.String(); want != have {
+			t.Fatalf("expected %s got %s", want, have)
+		}
+		if want, have := testCase.compressed, WIF.Compressed; want != have {
+			t.Fatalf("expected %v got %v", want, have)
+		}
+		if want, have := testCase.version, WIF.Version; want != have {
+			t.Fatalf("expected %d got %d", want, have)
+		}
+	}
+}
 @ -1 +1 @@
 .18.0
 .19.0