Function RecoverPubkey

crypto/secp256k1/secp256.go:101–118

RecoverPubkey returns the public key of the signer. msg must be the 32-byte hash of the message to be signed. sig must be a 65-byte compact ECDSA signature containing the recovery id as the last element.

(msg []byte, sig []byte)

// sig must be a 65-byte compact ECDSA signature containing the
// recovery id as the last element.
func RecoverPubkey(msg []byte, sig []byte) ([]byte, error) {
	if len(msg) != 32 {
		return nil, ErrInvalidMsgLen
	}
	if err := checkSignature(sig); err != nil {
		return nil, err
	}

	var (
		pubkey  = make([]byte, 65)
		sigdata = (*C.uchar)(unsafe.Pointer(&sig[0]))
		msgdata = (*C.uchar)(unsafe.Pointer(&msg[0]))
	)
	if C.secp256k1_ext_ecdsa_recover(context, (*C.uchar)(unsafe.Pointer(&pubkey[0])), sigdata, msgdata) == 0 {
		return nil, ErrRecoverFailed
	}
	return pubkey, nil
}

// VerifySignature checks that the given pubkey created signature over message.
// The signature should be in [R || S] format.