Exemple #1
0
func FuncOP_CHECKSIG(s *Stack, data *Data) error {
	if data == nil || data.Hasher == nil {
		return fmt.Errorf("Requires a hasher.")
	}
	pk, err := s.PopData()
	if err != nil {
		return err
	}
	x, y, err := utils.ParsePublicKey(pk)
	if err != nil {
		return fmt.Errorf("Failed to parse public key: %v", err)
	}
	pubKey := bitecdsa.PublicKey{bitelliptic.S256(), x, y}

	sn, err := s.PopData()
	if err != nil {
		return err
	}
	sign, hashCode := sn[:len(sn)-1], sn[len(sn)-1]
	R, S, err := utils.DERDecode(sign)
	if err != nil {
		return fmt.Errorf("Failed to parse signature: %v", err)
	}
	hash := data.Hasher(uint32(hashCode))
	if bitecdsa.Verify(&pubKey, hash, R, S) {
		s.PushBool(true)
	} else {
		s.PushBool(false)
	}
	return nil
}
func ParseCompact(b []byte) (*big.Int, *big.Int, error) {
	if len(b) != 33 {
		return nil, nil, fmt.Errorf("Data \"%x\" isn't 33 bytes.", b)
	}
	curve := bitelliptic.S256()

	// y = sqrt(x^3 + B) mod P
	x := new(big.Int).SetBytes(b[1:33])
	x3 := new(big.Int).Mul(x, x)
	x3.Mul(x3, x)
	y2 := new(big.Int).Add(x3, curve.B)
	y2.Mod(y2, curve.P)

	// sqrt(a) = a^((P+1)/4)
	e := big.NewInt(1)
	e = e.Add(e, curve.P)
	e = e.Div(e, big.NewInt(4))
	y := y2.Exp(y2, e, curve.P)

	switch b[0] {
	case 0x02:
		// y should be even.
		if y.Bit(0) == 1 {
			y = y.Sub(curve.P, y)
		}
	case 0x03:
		// y should be odd.
		if y.Bit(0) == 0 {
			y = y.Sub(curve.P, y)
		}
	default:
		// TODO consider panicking if functions is private.
		return nil, nil, fmt.Errorf("Bad prefix 0x%x.", b[0])
	}
	return x, y, nil
}