cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(keybytes, "AES"), new IvParameterSpec(ZERO_IV, 0, ZERO_IV.length));
        if ( constant.length != cipher.getBlockSize() ) {
            constant = expandNFold(constant, cipher.getBlockSize());
        }
        byte[] enc = constant;
        int klen = keybytes.length;
        byte[] dk = new byte[klen];
        for ( int n = 0; n < klen; ) {