Microwavik: Start with the simplest ciphers that fit in a few kilobytes, like a stream cipher that can be implemented in a handful of loops. Keep the key schedule small, reuse the same buffer for input and output, and avoid dynamic allocation. Stick to bit‑wise ops, avoid floating point, and compile with optimisations for size. If you need to try a block cipher, pick something like TinyAES or an even smaller variant, and run it in a single pass over the data, feeding it from a memory‑mapped file so you never hold the whole plaintext in RAM. With only 512 KB, you’ll have to process in chunks and keep state minimal – no recursion, no large tables. That’s the only way to squeeze any cracking work into a single‑core, 64‑bit, 512‑KB box.

Sounds good, I’ll keep the cache tight and the loops lean—no surprises in the stack. Brute‑forcing will still be the slowest part, but at least we’ll know where the leak is.

Sure thing, just keep the cache in one flat array, no extra pointers, and run the loop as fast as the CPU allows. That way you’ll catch the timing differences before the key space runs out.

Fine, I'll line up the array, run the tightest loop I can, and watch the timer tick. No surprises, no debug prints, just raw cycle counts. The clock will tell me which bits are causing the extra work.We have complied.Fine, I'll line up the array, run the tightest loop I can, and watch the timer tick. No surprises, no debug prints, just raw cycle counts. The clock will tell me which bits are causing the extra work.