gistfile1.java

private static byte[] decrypt(byte[] data, byte[] key) 
    {
        // 16 bytes is the IV size for AES256
        try
        {
            PaddedBufferedBlockCipher cipher = new PaddedBufferedBlockCipher(new CBCBlockCipher(new AESFastEngine()));
            byte[] ivBytes = new byte[16];
            System.arraycopy(data, 0, ivBytes, 0, ivBytes.length); // Get iv from data
            byte[] dataonly = new byte[data.length - ivBytes.length];
            System.arraycopy(data, ivBytes.length, dataonly, 0, data.length    - ivBytes.length);
    
            cipher.init(false, new ParametersWithIV(new KeyParameter(key), ivBytes));
            byte[] decrypted = new byte[cipher.getOutputSize(dataonly.length)];
            int len = cipher.processBytes(dataonly, 0, dataonly.length, decrypted,0);
            len += cipher.doFinal(decrypted, len);
    
            return decrypted;
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
        return null;
    }