5 ms·
Aren't cryptographic random number generators, still PRNGs. It sounds a fun problem, predicting the future random numbers, going to have to have a play later a
by anfractuosity 9y ago
Aren't cryptographic random number generators, still PRNGs.
It sounds a fun problem, predicting the future random numbers, going to have to have a play later at trying it.
- hlieberman 9y agoYes. GP is mistaken here; this is novel work that is somewhat concerning -- mostly in how it might apply to other similarly state-based RNGs.
- pbnjay 9y agoI made no comment on the work done here, it is novel and concerning if you use the outputs for important things. My comment is that non-cryptographic random number generators should not be used for security-critical functions. These functions are specifically built for speed, not security.
- karanlyons 9y agoI wouldn’t say this work is novel in the general case of “PRNGs are not CSPRNGs”. You can throw a constraint solver at most any PRNG and given sufficient output determine the state fairly easily. As a datapoint, doing this for xoroshiro took me half an hour: https://gist.github.com/karanlyons/805dbcc9e898dbd17e06f2627d5f9111 https://gist.github.com/karanlyons/805dbcc9e898dbd17e06f2627...
- anfractuosity 9y agoHeh, that sounds cool. I'll save opening that link for later.
- karanlyons 9y agoDon’t worry, it’s safe: I didn’t put the actual solver, just proof that I solved it. Wouldn’t want to spoil the fun for anyone else :)
- DiThi 9y agoStrong crypto RNGs use PRNGs but combines sources of entropy, environmental noise from devices such as the number of CPU cycles between user keystrokes. T̶h̶a̶t̶'̶s̶ ̶t̶h̶e̶ ̶d̶i̶f̶f̶e̶r̶e̶n̶c̶e̶ ̶b̶e̶t̶w̶e̶e̶n̶ ̶/̶d̶e̶v̶/̶r̶a̶n̶d̶o̶m̶ ̶a̶n̶d̶ ̶/̶d̶e̶v̶/̶u̶r̶a̶n̶d̶o̶m̶ ̶i̶n̶ ̶L̶i̶n̶u̶x̶.̶
- Tomte 9y agoNo, that difference (between /dev/random and /dev/urandom) does not exist, has never existed and will never exist. Please don't spread those myths.
- andruby 9y agoAs I am uninformed on the subject, could you tell me the difference between /dev/random and /dev/urandom?
- filleokus 9y agoQuite a long read, but I think it explains the situation quite well: https://www.2uo.de/myths-about-urandom/ https://www.2uo.de/myths-about-urandom/
- snakeanus 9y agoAlso an interesting and related article https://sockpuppet.org/blog/2014/02/25/safely-generate-random-numbers/ https://sockpuppet.org/blog/2014/02/25/safely-generate-rando...
- Tomte 9y agoUnfortunately, the article isn't in the best shape right now. Back when it was written, things were clear: random and urandom are the same. Then came getrandom as a distraction. Now urandom is based on chacha. So it's different (but not worse – still, harder to explain). The article's structure couldn't easily accomodate those changes, and time was and is in short supply, and so it's not wrong, but much less forceful and clear than it used to be. I hope it shapes up soon, but don't promise anything! Still, I don't know a more up-to-date article. Maybe Thomas Pornin has something newer on StackOverflow?