----- Forwarded message from John Gilmore
I'll be the first to admit that I don't understand this paper. I'm just an engineer, not a mathematician. But it looks to me like the authors are academics, who create an imaginary construction method for a random number generator, then prove that /dev/random is not the same as their method, and then suggest that /dev/random be revised to use their method, and then show how much faster their method is. All in all it seems to be a pitch for their method, not a serious critique of /dev/random. They labeled one of their construction methods "robustness", but it doesn't mean what you think the word means. It's defined by a mess of greek letters like this: Theorem 2. Let n > m, , ?? ??? be integers. Assume that G : {0, 1}m ??? {0, 1}n+ is a deterministic (t, ??prg )- pseudorandom generator. Let G = (setup, refresh, next) be defined as above. Then G is a ((t , qD , qR , qS ), ?? ??? , ??)- 2 robust PRNG with input where t ??? t, ?? = qR (2??prg +qD ??ext +2???n+1 ) as long as ?? ??? ??? m+2 log(1/??ext )+1, n ??? m + 2 log(1/??ext ) + log(qD ) + 1. Yeah, what he said! Nowhere do they seem to show that /dev/random is actually insecure. What they seem to show is that it does not meet the "robustness" criterion that they arbitrarily picked for their own construction. Their key test is on pages 23-24, and begins with "After a state compromise, A (the adversary) knows all parameters." The comparison STARTS with the idea that the enemy has figured out all of the hidden internal state of /dev/random. Then the weakness they point out seems to be that in some cases of new, incoming randomness with mis-estimated entropy, /dev/random doesn't necessarily recover over time from having had its entire internal state somehow compromised. This is not very close to what "/dev/random is not robust" means in English. Nor is it close to what others might assume the paper claims, e.g. "/dev/random is not safe to use". John PS: After attending a few crypto conferences, I realized that academic pressures tend to encourage people to write incomprehensible papers, apparently because if nobody reading their paper can understand it, then they look like geniuses. But when presenting at a conference, if nobody in the crowd can understand their slides, then they look like idiots. So the key to understanding somebody's incomprehensible paper is to read their slides and watch their talk, 80% of which is often explanations of the background needed to understand the gibberish notations they invented in the paper. I haven't seen either the slides or the talk relating to this paper. _______________________________________________ The cryptography mailing list cryptography@metzdowd.com http://www.metzdowd.com/mailman/listinfo/cryptography ----- End forwarded message ----- -- Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org ______________________________________________________________ ICBM: 48.07100, 11.36820 http://ativel.com http://postbiota.org AC894EC5: 38A5 5F46 A4FF 59B8 336B 47EE F46E 3489 AC89 4EC5