Autentication symmetric

Security.java

public byte[] autenticacao(byte[] input, SecretKey secret) throws DataLengthException, InvalidCipherTextException {
	CBCBlockCipher cbcBlockCipher = new CBCBlockCipher(new AESEngine());
	//SecureRandom random = new SecureRandom();
	BlockCipherPadding bcp = new PKCS7Padding();
	PaddedBufferedBlockCipher pbbc = new PaddedBufferedBlockCipher(cbcBlockCipher, bcp);

	int blockSize = cbcBlockCipher.getBlockSize();
	int inputOffset = 0;
	int inputLength = input.length;
	int outputOffset = 0;

	byte[] iv = new byte[blockSize];
	outputOffset += blockSize;

	pbbc.init(true, new ParametersWithIV(new KeyParameter(secret.getEncoded()), iv));
	byte[] output = new byte[pbbc.getOutputSize(inputLength) + outputOffset];

	System.arraycopy(iv, 0, output, 0, blockSize);

	int outputLength = outputOffset + pbbc.processBytes(input, inputOffset, inputLength, output, outputOffset);

	outputLength += pbbc.doFinal(output, outputLength);

	//Pego apenas o último bloco
	byte[] out = new byte[blockSize];
	System.arraycopy(output, outputLength - blockSize, out, 0, blockSize);

	return out;
}

private byte[] process(byte[] input, boolean encrypt, SecretKey secret) throws DataLengthException, IllegalStateException, InvalidCipherTextException {
	CBCBlockCipher cbcBlockCipher = new CBCBlockCipher(new AESEngine());
	BlockCipherPadding bcp = new PKCS7Padding();
	PaddedBufferedBlockCipher pbbc = new PaddedBufferedBlockCipher(cbcBlockCipher, bcp);

	int blockSize = cbcBlockCipher.getBlockSize();
	int inputOffset = 0;
	int inputLength = input.length;
	int outputOffset = 0;

	byte[] iv = new byte[blockSize];
	if (encrypt) {
		//random.nextBytes(iv);
		outputOffset += blockSize;
	} else {
		System.arraycopy(input, 0, iv, 0, blockSize);
		inputOffset += blockSize;
		inputLength -= blockSize;
	}

	pbbc.init(encrypt, new ParametersWithIV(new KeyParameter(secret.getEncoded()), iv));
	byte[] output = new byte[pbbc.getOutputSize(inputLength) + outputOffset];

	if (encrypt) {
		System.arraycopy(iv, 0, output, 0, blockSize);
	}

	int outputLength = outputOffset + pbbc.processBytes(input, inputOffset, inputLength, output, outputOffset);

	outputLength += pbbc.doFinal(output, outputLength);

	byte[] out = new byte[outputLength];
	System.arraycopy(output, 0, out, 0, outputLength);

	return out;
}