func SignMessage(privKey string, message string, compress bool) string {
prefixBytes := []byte("Bitcoin Signed Message:\n")
messageBytes := []byte(message)
bytes := []byte{}
bytes = append(bytes, byte(len(prefixBytes)))
bytes = append(bytes, prefixBytes...)
bytes = append(bytes, byte(len(messageBytes)))
bytes = append(bytes, messageBytes...)
privKeyBytes := HexDecode(privKey)
x, y := btcec.S256().ScalarBaseMult(privKeyBytes)
ecdsaPubKey := ecdsa.PublicKey{
Curve: btcec.S256(),
X: x,
Y: y,
}
ecdsaPrivKey := &ecdsa.PrivateKey{
PublicKey: ecdsaPubKey,
D: new(big.Int).SetBytes(privKeyBytes),
}
sigbytes, err := btcec.SignCompact(btcec.S256(), ecdsaPrivKey, btcwire.DoubleSha256(bytes), compress)
if err != nil {
panic(err)
}
return base64.StdEncoding.EncodeToString(sigbytes)
}
func testSignCompact(t *testing.T, tag string, curve *btcec.KoblitzCurve,
data []byte, isCompressed bool) {
priv, _ := ecdsa.GenerateKey(curve, rand.Reader)
hashed := []byte("testing")
sig, err := btcec.SignCompact(curve, priv, hashed, isCompressed)
if err != nil {
t.Errorf("%s: error signing: %s", tag, err)
return
}
pk, wasCompressed, err := btcec.RecoverCompact(curve, sig, hashed)
if err != nil {
t.Errorf("%s: error recovering: %s", tag, err)
return
}
if pk.X.Cmp(priv.X) != 0 || pk.Y.Cmp(priv.Y) != 0 {
t.Errorf("%s: recovered pubkey doesn't match original "+
"(%v,%v) vs (%v,%v) ", tag, pk.X, pk.Y, priv.X, priv.Y)
return
}
if wasCompressed != isCompressed {
t.Errorf("%s: recovered pubkey doesn't match compressed state "+
"(%v vs %v)", tag, isCompressed, wasCompressed)
return
}
// If we change the compressed bit we should get the same key back,
// but the compressed flag should be reversed.
if isCompressed {
sig[0] -= 4
} else {
sig[0] += 4
}
pk, wasCompressed, err = btcec.RecoverCompact(curve, sig, hashed)
if err != nil {
t.Errorf("%s: error recovering (2): %s", tag, err)
return
}
if pk.X.Cmp(priv.X) != 0 || pk.Y.Cmp(priv.Y) != 0 {
t.Errorf("%s: recovered pubkey (2) doesn't match original "+
"(%v,%v) vs (%v,%v) ", tag, pk.X, pk.Y, priv.X, priv.Y)
return
}
if wasCompressed == isCompressed {
t.Errorf("%s: recovered pubkey doesn't match reversed "+
"compressed state (%v vs %v)", tag, isCompressed,
wasCompressed)
return
}
}
