Added Encrypt & Decrypt using the ECIES w/ tests

crypto/crypto.go

 package crypto
 
 import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
 	"crypto/sha256"
 
 	"code.google.com/p/go.crypto/ripemd160"
 	"github.com/ethereum/go-ethereum/ethutil"
+	"github.com/obscuren/ecies"
 	"github.com/obscuren/secp256k1-go"
 	"github.com/obscuren/sha3"
 )
 
+func init() {
+	// specify the params for the s256 curve
+	ecies.AddParamsForCurve(S256(), ecies.ECIES_AES128_SHA256)
+}
+
+func ToECDSA(prv []byte) *ecdsa.PrivateKey {
+	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 {
+	return prv.D.Bytes()
+}
+
 // TODO refactor, remove (bin)
 func Sha3(data []byte) []byte {
 	d := sha3.NewKeccak256()
@@ -45,3 +66,24 @@ func Ecrecover(data []byte) []byte {
 
 	return r
 }
+
+func SigToPub(hash, sig []byte) []byte {
+	return Ecrecover(append(hash, sig...))
+}
+
+func Sign(hash, prv []byte) (sig []byte, err error) {
+	sig, err = secp256k1.Sign(hash, prv)
+	return
+}
+
+func Encrypt(pub, message []byte) ([]byte, error) {
+	x, y := elliptic.Unmarshal(S256(), pub)
+	epub := &ecdsa.PublicKey{S256(), x, y}
+
+	return ecies.Encrypt(rand.Reader, ecies.ImportECDSAPublic(epub), message, nil, nil)
+}
+
+func Decrypt(prv, ct []byte) ([]byte, error) {
+	key := ecies.ImportECDSA(ToECDSA(prv))
+	return key.Decrypt(rand.Reader, ct, nil, nil)
+}

crypto/encrypt_decrypt_test.go

+package crypto
+
+import (
+	"bytes"
+	"fmt"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/ethutil"
+)
+
+func TestBox(t *testing.T) {
+	prv1 := ethutil.Hex2Bytes("4b50fa71f5c3eeb8fdc452224b2395af2fcc3d125e06c32c82e048c0559db03f")
+	prv2 := ethutil.Hex2Bytes("d0b043b4c5d657670778242d82d68a29d25d7d711127d17b8e299f156dad361a")
+	pub2 := ethutil.Hex2Bytes("04bd27a63c91fe3233c5777e6d3d7b39204d398c8f92655947eb5a373d46e1688f022a1632d264725cbc7dc43ee1cfebde42fa0a86d08b55d2acfbb5e9b3b48dc5")
+
+	message := []byte("Hello, world.")
+	ct, err := Encrypt(pub2, message)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	pt, err := Decrypt(prv2, ct)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	if !bytes.Equal(pt, message) {
+		fmt.Println("ecies: plaintext doesn't match message")
+		t.FailNow()
+	}
+
+	_, err = Decrypt(prv1, pt)
+	if err == nil {
+		fmt.Println("ecies: encryption should not have succeeded")
+		t.FailNow()
+	}
+
+}