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package crypto

import (
    "crypto/ecdsa"
    "crypto/elliptic"
    "crypto/rand"
    "crypto/sha256"

    "code.google.com/p/go.crypto/ripemd160"
    "github.com/ethereum/go-ethereum/crypto/sha3"
    "github.com/ethereum/go-ethereum/ethutil"
    "github.com/obscuren/ecies"
    "github.com/obscuren/secp256k1-go"
)

func init() {
    // specify the params for the s256 curve
    ecies.AddParamsForCurve(S256(), ecies.ECIES_AES128_SHA256)
}

func Sha3(data []byte) []byte {
    d := sha3.NewKeccak256()
    d.Write(data)

    return d.Sum(nil)
}

// Creates an ethereum address given the bytes and the nonce
func CreateAddress(b []byte, nonce uint64) []byte {
    return Sha3(ethutil.NewValue([]interface{}{b, nonce}).Encode())[12:]
}

func Sha256(data []byte) []byte {
    hash := sha256.Sum256(data)

    return hash[:]
}

func Ripemd160(data []byte) []byte {
    ripemd := ripemd160.New()
    ripemd.Write(data)

    return ripemd.Sum(nil)
}

func Ecrecover(data []byte) []byte {
    var in = struct {
        hash []byte
        sig  []byte
    }{data[:32], data[32:]}

    r, _ := secp256k1.RecoverPubkey(in.hash, in.sig)

    return r
}

// New methods using proper ecdsa keys from the stdlib
func ToECDSA(prv []byte) *ecdsa.PrivateKey {
    if len(prv) == 0 {
        return nil
    }

    priv := new(ecdsa.PrivateKey)
    priv.PublicKey.Curve = S256()
    priv.D = ethutil.BigD(prv)
    priv.PublicKey.X, priv.PublicKey.Y = S256().ScalarBaseMult(prv)
    return priv
}

func FromECDSA(prv *ecdsa.PrivateKey) []byte {
    if prv == nil {
        return nil
    }
    return prv.D.Bytes()
}

func ToECDSAPub(pub []byte) *ecdsa.PublicKey {
    if len(pub) == 0 {
        return nil
    }
    x, y := elliptic.Unmarshal(S256(), pub)
    return &ecdsa.PublicKey{S256(), x, y}
}

func FromECDSAPub(pub *ecdsa.PublicKey) []byte {
    if pub == nil {
        return nil
    }
    return elliptic.Marshal(S256(), pub.X, pub.Y)
}

func GenerateKey() (*ecdsa.PrivateKey, error) {
    return ecdsa.GenerateKey(S256(), rand.Reader)
}

func SigToPub(hash, sig []byte) *ecdsa.PublicKey {
    s := Ecrecover(append(hash, sig...))
    x, y := elliptic.Unmarshal(S256(), s)

    return &ecdsa.PublicKey{S256(), x, y}
}

func Sign(hash []byte, prv *ecdsa.PrivateKey) (sig []byte, err error) {
    sig, err = secp256k1.Sign(hash, prv.D.Bytes())
    return
}

func Encrypt(pub *ecdsa.PublicKey, message []byte) ([]byte, error) {
    return ecies.Encrypt(rand.Reader, ecies.ImportECDSAPublic(pub), message, nil, nil)
}

func Decrypt(prv *ecdsa.PrivateKey, ct []byte) ([]byte, error) {
    key := ecies.ImportECDSA(prv)
    return key.Decrypt(rand.Reader, ct, nil, nil)
}