play

public static byte[] AES_decrypt(byte[] inputData) throws CryptoException, IOException {

        byte[] keyData = "Hello world".getBytes();
        AESKey key = new AESKey(keyData, 0, 256);

        AESDecryptorEngine engine = new AESDecryptorEngine(key);
        PKCS5UnformatterEngine uengine = new PKCS5UnformatterEngine(engine);

        ByteArrayInputStream input = new ByteArrayInputStream(inputData);
        BlockDecryptor decryptor = new BlockDecryptor(uengine, input);
        byte[] plaintextAndHash = new byte[1024];
        ByteArrayOutputStream output = new ByteArrayOutputStream();
        int bytesRead=0;

        do {
            bytesRead =decryptor.read(plaintextAndHash);
            if(bytesRead!=-1){
                output.write(plaintextAndHash,0,bytesRead);
            }
        } while ( bytesRead != -1 );

        return output.toByteArray();
    }

    public static byte[] AES_decrypt2(byte[] inputData) throws CryptoException, IOException {
        byte[] keyData = calculateMD5("Hello world");
        AESKey aesKey = new AESKey(keyData);

        AESDecryptorEngine engine = new AESDecryptorEngine(aesKey);
        PKCS5UnformatterEngine uengine = new PKCS5UnformatterEngine(engine);

        ByteArrayInputStream istream = new ByteArrayInputStream(inputData);
        BlockDecryptor decryptor = new BlockDecryptor(uengine, istream);

        byte[] temp = new byte[100];
        DataBuffer dbuff = new DataBuffer();
        int bytesRead = 0;

        for (;;){
            bytesRead = decryptor.read(temp);
            dbuff.write(temp, 0, bytesRead);
            if (bytesRead < 100) break;
        }

        byte[] plainData = dbuff.getArray();
        int plainDataLength = plainData.length - SHA1Digest.DIGEST_LENGTH;
        byte[] decryptedData = new byte[plainDataLength];
        byte[] hash = new byte[SHA1Digest.DIGEST_LENGTH];

        System.arraycopy(plainData, 0, decryptedData, 0, plainDataLength);
        System.arraycopy(plainData, plainDataLength, hash, 0, SHA1Digest.DIGEST_LENGTH);

        SHA1Digest digest = new SHA1Digest();
        digest.update(plainData);
        byte[] hash2 = digest.getDigest();

        if (!Arrays.equals(hash, hash2)) throw new RuntimeException();

        return decryptedData;
    }

    private static byte[] calculateMD5(String input){
        byte[] plain = input.getBytes();
        MD5 md5 = new MD5(plain);
        return md5.doFinal();
    }