signmessage.java

private static String signMessageByteArray(String message,
		PGPSecretKey pgpSec, char pass[]) throws IOException,
		NoSuchAlgorithmException, NoSuchProviderException, PGPException,
		SignatureException {
	byte[] messageCharArray = message.getBytes();

	ByteArrayOutputStream encOut = new ByteArrayOutputStream();
	OutputStream out = encOut;
	out = new ArmoredOutputStream(out);

	// Unlock the private key using the password
	PGPPrivateKey pgpPrivKey = pgpSec
		.extractPrivateKey(new JcePBESecretKeyDecryptorBuilder()
		.setProvider("BC").build(pass));

	// Signature generator, we can generate the public key from the private key! Nifty!
	PGPSignatureGenerator sGen = new PGPSignatureGenerator(
		new JcaPGPContentSignerBuilder(pgpSec.getPublicKey()
				.getAlgorithm(), PGPUtil.SHA1).setProvider("BC"));

	sGen.init(PGPSignature.BINARY_DOCUMENT, pgpPrivKey);

	Iterator it = pgpSec.getPublicKey().getUserIDs();
	if (it.hasNext()) {
		PGPSignatureSubpacketGenerator spGen = new PGPSignatureSubpacketGenerator();
		spGen.setSignerUserID(false, (String) it.next());
		sGen.setHashedSubpackets(spGen.generate());
	}

	PGPCompressedDataGenerator comData = new PGPCompressedDataGenerator(
		PGPCompressedData.ZLIB);

	BCPGOutputStream bOut = new BCPGOutputStream(comData.open(out));

	sGen.generateOnePassVersion(false).encode(bOut);

	PGPLiteralDataGenerator lGen = new PGPLiteralDataGenerator();
	OutputStream lOut = lGen.open(bOut, PGPLiteralData.BINARY,
	PGPLiteralData.CONSOLE, messageCharArray.length, new Date());	
	
	for (byte c : messageCharArray) {
		lOut.write(c);
		sGen.update(c);
	}

	lOut.close();

	lGen.close();

	sGen.generate().encode(bOut);

	comData.close();

	out.close();

	return encOut.toString();
}