org.bouncycastle.asn1.x509.DigestInfo Java Examples

public static BigInteger EMSA_PKCS1_V1_5_ENCODE(byte[] input, final BigInteger modulus)
		throws NoSuchAlgorithmException, IOException {

	// Digest the input
	final MessageDigest md = MessageDigest.getInstance(HASH_ALGORITHM);
	final byte[] digest = md.digest(input);

	// Create a digest info consisting of the algorithm id and the hash
	final AlgorithmIdentifier algId = new AlgorithmIdentifier(NISTObjectIdentifiers.id_sha512, DERNull.INSTANCE);
	final DigestInfo digestInfo = new DigestInfo(algId, digest);
	final byte[] message = digestInfo.getEncoded(ASN1Encoding.DER);

	// Do PKCS1 padding
	final byte[] block = new byte[(modulus.bitLength() / 8) - 1];
	System.arraycopy(message, 0, block, block.length - message.length, message.length);
	block[0] = 0x01; // type code 1
	for (int i = 1; i != block.length - message.length - 1; i++) {
		block[i] = (byte) 0xFF;
	}

	return new BigInteger(1, block);
}
 

/*** Static Methods ***/

	private static BigInteger EMSA_PKCS1_V1_5_ENCODE(byte[] input, final BigInteger modulus)
			throws NoSuchAlgorithmException, IOException {

		// Digest the input
		final MessageDigest md = MessageDigest.getInstance(HASH_ALGORITHM);
		final byte[] digest = md.digest(input);

		// Create a digest info consisting of the algorithm id and the hash
		final AlgorithmIdentifier algId = new AlgorithmIdentifier(NISTObjectIdentifiers.id_sha512, DERNull.INSTANCE);
		final DigestInfo digestInfo = new DigestInfo(algId, digest);
		final byte[] message = digestInfo.getEncoded(ASN1Encoding.DER);

		// Do PKCS1 padding
		final byte[] block = new byte[((modulus.bitLength() + 7) / 8) - 1];
		System.arraycopy(message, 0, block, block.length - message.length, message.length);
		block[0] = 0x01; // type code 1
		for (int i = 1; i != block.length - message.length - 1; i++) {
			block[i] = (byte) 0xFF;
		}

		return new BigInteger(1, block);
	}
 

/**
 * <a href="http://stackoverflow.com/questions/33305800/difference-between-sha256withrsa-and-sha256-then-rsa">
 * Difference between SHA256withRSA and SHA256 then RSA
 * </a>
 * <p>
 * This method is the updated code provided by the OP. As expected it shows two equal signatures.
 * The OP's observations seem to differ, though.
 * </p>
 */
public void testAsGreenhandUpdated(PrivateKey privateKey) throws GeneralSecurityException, IOException
{
    System.out.println("\nGreenhandUpdated:");

    String s = "1234";
    MessageDigest messageDigest = MessageDigest.getInstance("SHA-256");
    messageDigest.update(s.getBytes());
    byte[] outputDigest = messageDigest.digest();

    AlgorithmIdentifier sha256Aid = new AlgorithmIdentifier(NISTObjectIdentifiers.id_sha256, DERNull.INSTANCE);
    DigestInfo di = new DigestInfo(sha256Aid, outputDigest);
    //sign SHA256 with RSA
    Signature rsaSignature = Signature.getInstance("RSA");
    rsaSignature.initSign(privateKey);
    byte[] encodedDigestInfo = di.toASN1Primitive().getEncoded();
    rsaSignature.update(encodedDigestInfo);
    byte[] signed = rsaSignature.sign();
    System.out.println("method 1: "+bytesToHex(signed));
    System.out.println("    hash: " + bytesToHex(outputDigest));
    System.out.println("    algo: " + sha256Aid.getAlgorithm());
    System.out.println("    info: " + bytesToHex(encodedDigestInfo));

    //compute SHA256withRSA as a single step
    Signature rsaSha256Signature = Signature.getInstance("SHA256withRSA");
    rsaSha256Signature.initSign(privateKey);
    rsaSha256Signature.update(s.getBytes());
    byte[] signed2 = rsaSha256Signature.sign();
    System.out.println("method 2: "+bytesToHex(signed2));
}
 

private byte[] derEncode(byte[] hash) throws IOException {
  if (digestAlgId == null) {
    // For raw RSA, the DigestInfo must be prepared externally
    return hash;
  }

  DigestInfo digestInfo = new DigestInfo(digestAlgId, hash);
  return digestInfo.getEncoded(ASN1Encoding.DER);
}
 

/**
 * This method wraps the digest value in a DigestInfo (combination of digest
 * algorithm and value). This encapsulation is required to operate NONEwithRSA
 * signatures.
 * 
 * @param digestAlgorithm
 *                        the used digest algorithm
 * @param digest
 *                        the digest value
 * @return DER encoded binaries of the related digest info
 */
public static byte[] encodeRSADigest(final DigestAlgorithm digestAlgorithm, final byte[] digest) {
	try {
		AlgorithmIdentifier algId = new AlgorithmIdentifier(new ASN1ObjectIdentifier(digestAlgorithm.getOid()), DERNull.INSTANCE);
		DigestInfo digestInfo = new DigestInfo(algId, digest);
		return digestInfo.getEncoded(ASN1Encoding.DER);
	} catch (IOException e) {
		throw new DSSException("Unable to encode digest", e);
	}
}