5 ms·

Both /dev/random and /dev/urandom use the same PRNG...

• shawnz 12y ago
  But /dev/random has the additional constraint that it will stop outputting if that PRNG hasn't been reseeded in [some reasonable amount of time/output bits]. So you are guaranteed to get bits that have come from a recently-seeded PRNG, rather than any old PRNG. I have had this argument on here before and the conclusion was that it's not a real issue, but I think this is what the parent poster is talking about. EDIT: Thanks for the clarification tptacek. I don't mean to disagree -- in fact it was you who explained this to me last time as well.
  • tptacek 12y ago
    "Recently" seeded isn't a meaningful distinction. It has either been "seeded" or it hasn't. The recency of the seed --- a point Linux's interface worries a great deal about --- has nothing to do with security.
    • hueving 12y ago
      >The recency of the seed --- a point Linux's interface worries a great deal about --- has nothing to do with security. Unless you are concerned about where the seed came from (e.g. not storage like /var/run/random-seed) or have any concerns that there is a flaw in the PRNG that could leak information.
      • X-Istence 12y ago
        If you are concerned that your PRNG is broken, then you can't trust crypto in general. Doesn't matter how often you reseed your PRNG.
• hueving 12y ago
  Right, and if it is flawed to long term analysis in some way, you want it to be frequently re-seeded.