enc = block;
        }
        return dk;
    }


    public static byte[] expandNFold ( byte[] data, int outlen ) {
        int lcm = lcm(outlen, data.length);
        byte[] buf = new byte[outlen];
        int carry = 0;
        for ( int i = lcm - 1; i >= 0; i-- ) {
            carry = carry_add(data, buf, carry, i);
        }

        if ( carry != 0 ) {