claude

#HowTo get #entropy for #PRNG #PseudoRandomNumberGeneration on old hardware? #nondeterministic #RetroComputing

My #Amiga #A500 running my software makes the same sounds in the same order when powered on, when I really want it to be different each time. I seed based on `time()` but either libc from VBCC does not support it or the machine has no battery-backed real time clock or both.

Maybe I could use a #ParallelPort #sampler cartridge and hope its noise floor isn't too good? Allocate memory without clearing and hash it before using it (would that survive a cold boot?).

Sep 24, 2021 at 1:07pmWeb
Show threadCsepp 🌢Sep 27, 2021
@mathr AFAIK Linux can use IO timings, but if the user isn't using the input peripherals then I'm not sure what hardware you could use. Maybe the least significant bits of HDD timing are random enough???
Show threadEd SSep 27, 2021

Yep timing from any inputs and from rotating media is a source of entropy. Just hash everything you've got: you can't make the situation worse by doing that. Uncleared memory too: again, doesn't matter if it happens to be predictable, the hash isn't harmed.

If you have analogue inputs, then the input values are potential entropy sources too, whether or not anything is connected.

@csepp @mathr

Show threadCsepp 🌢Sep 29, 2021

@EdS @mathr Came across this while researching something we learned on an unrelated class:
https://peteroupc.github.io/randextract.html
http://www.eecs.harvard.edu/~michaelm/coinflipext.pdf

Useful if you wanna make sure your random bits aren't biased.

A Note on Randomness Extraction