public static BigInteger signedMessageToKey(byte[] message, SignatureData signatureData)
            throws SignatureException {
        return signedMessageHashToKey(Hash.sha3(message), signatureData);
    }
@Test
    public void testSignedMessageToKey() throws SignatureException {
        Sign.SignatureData signatureData =
                Sign.signPrefixedMessage(TEST_MESSAGE, SampleKeys.KEY_PAIR);
        BigInteger key = Sign.signedPrefixedMessageToKey(TEST_MESSAGE, signatureData);
        assertEquals(key, (SampleKeys.PUBLIC_KEY));
    }