EncryptWithRSA.java

package org.bouncycastle.openpgp.examples;

import org.bouncycastle.bcpg.ArmoredOutputStream;
import org.bouncycastle.bcpg.HashAlgorithmTags;
import org.bouncycastle.bcpg.SymmetricKeyAlgorithmTags;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.openpgp.*;
import org.bouncycastle.openpgp.jcajce.JcaPGPObjectFactory;
import org.bouncycastle.openpgp.operator.PGPDigestCalculator;
import org.bouncycastle.openpgp.operator.PublicKeyDataDecryptorFactory;
import org.bouncycastle.openpgp.operator.jcajce.*;
import org.bouncycastle.util.io.Streams;

import java.io.*;
import java.security.*;
import java.util.Date;

public class EncryptWithRSA {

	private static PGPPublicKey publicKey;
	private static PGPPrivateKey privateKey;

	public static byte[] createRsaEncryptedObject(PGPPublicKey encryptionKey, byte[] data)
			throws PGPException, IOException
	{
		ByteArrayOutputStream bOut = new ByteArrayOutputStream();
		PGPLiteralDataGenerator lData = new PGPLiteralDataGenerator();
		OutputStream pOut = lData.open(bOut,
				PGPLiteralData.BINARY,
				PGPLiteralData.CONSOLE,
				data.length,
				new Date());
		pOut.write(data);
		pOut.close();
		byte[] plainText = bOut.toByteArray();
		ByteArrayOutputStream encOut = new ByteArrayOutputStream();
		PGPEncryptedDataGenerator encGen = new PGPEncryptedDataGenerator(
				new JcePGPDataEncryptorBuilder(
						SymmetricKeyAlgorithmTags.AES_256)
						.setWithIntegrityPacket(true)
						.setSecureRandom(new SecureRandom())
						.setProvider("BC"));
		encGen.addMethod(new JcePublicKeyKeyEncryptionMethodGenerator(encryptionKey)
				.setProvider("BC"));

		OutputStream cOut = encGen.open(encOut, plainText.length);
		cOut.write(plainText);
		cOut.close();
		return encOut.toByteArray();
	}

	public static byte[] extractRsaEncryptedObject(PGPPrivateKey privateKey, byte[] pgpEncryptedData)
			throws PGPException, IOException
	{
		PGPObjectFactory pgpFact = new JcaPGPObjectFactory(pgpEncryptedData);
		PGPEncryptedDataList encList = (PGPEncryptedDataList)pgpFact.nextObject();
		// note: we can only do this because we know we match the first encrypted data object
		PGPPublicKeyEncryptedData encData = (PGPPublicKeyEncryptedData)encList.get(0);
		PublicKeyDataDecryptorFactory dataDecryptorFactory = new JcePublicKeyDataDecryptorFactoryBuilder()
				.setProvider("BC").build(privateKey);
		InputStream clear = encData.getDataStream(dataDecryptorFactory);
		byte[] literalData = Streams.readAll(clear);
		if (encData.verify())
		{
			PGPObjectFactory litFact = new JcaPGPObjectFactory(literalData);
			PGPLiteralData litData = (PGPLiteralData)litFact.nextObject();
			byte[] data = Streams.readAll(litData.getInputStream());
			return data;
		}
		throw new IllegalStateException("modification check failed");
	}

	private static void generateKeyPair() throws NoSuchProviderException, NoSuchAlgorithmException, PGPException {
		KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA", "BC");

		kpg.initialize(1024);

		KeyPair kp = kpg.generateKeyPair();
		PGPDigestCalculator sha1Calc = new JcaPGPDigestCalculatorProviderBuilder().build().get(HashAlgorithmTags.SHA1);
		PGPKeyPair          keyPair = new JcaPGPKeyPair(PGPPublicKey.RSA_GENERAL, kp, new Date());
		PGPSecretKey        secretKey = new PGPSecretKey(PGPSignature.DEFAULT_CERTIFICATION, keyPair, "test", sha1Calc, null, null, new JcaPGPContentSignerBuilder(keyPair.getPublicKey().getAlgorithm(), HashAlgorithmTags.SHA1), new JcePBESecretKeyEncryptorBuilder(PGPEncryptedData.CAST5, sha1Calc).setProvider("BC").build("test".toCharArray()));

		publicKey = secretKey.getPublicKey();
		privateKey = secretKey.extractPrivateKey(new JcePBESecretKeyDecryptorBuilder().setProvider("BC").build("test".toCharArray()));
	}

	public static void main(
			String[] args)
			throws Exception
	{
		Security.addProvider(new BouncyCastleProvider());
		generateKeyPair();

		byte[] encryptedText = createRsaEncryptedObject(publicKey, "text to encrypt".getBytes());
		System.out.println("encrypted text:" + new String(encryptedText));
		byte[] decryptedText = extractRsaEncryptedObject(privateKey, encryptedText);
		System.out.println("decrypted text:" + new String(decryptedText));
	}

}