It is trivial to generate a mostly-randomized bijective mapping of small integers to small integers with an xor and a little byte swapping, which is what the au

It is trivial to generate a mostly-randomized bijective mapping of small integers to small integers with an xor and a little byte swapping, which is what the author does with a built-in AES instruction. The OP's point is that this isn't a particularly interesting problem. The interesting problem is generating efficient bijective mappings of large integers to very small integers.