[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Tue, 20 Oct 2015 20:26:55 +0300
From: gremlin@...mlin.ru
To: oss-security@...ts.openwall.com
Subject: Re: Prime example of a can of worms
On 2015-10-20 10:22:40 -0600, Kurt Seifried wrote:
> 1) in openssl does the -2/-5 option matter with respect to
> security?
Actually, no: it's just a "generator", so it can be almost any small
prime number - say, 3 or 7 or whatever. It can even be just co-prime
to group modulo base.
However, the value 2 is the default in OpenSSL, so there may be some
space for experiments with birthdays paradox... especially when the
modulo is small.
> 2) Openssl/gnutls (and likely others) all apparently have
> slight variations on how they generate/test primes [...]
> this worries me, diversity is good, but if not implemented
> correctly. Do any best practices actually exist?
All implementations I know of simply use the randomized algorithms
with Miller-Rabin primality test.
> 3) in testing for primeness how sure are we? Reading
[wikipedia: "Miller-Rabin primality test"]
> and so on these tests are all "probably prime" but I can't find
> any data to show that e.g. given this set of large primes, tested
> against the various traditional primality methods, and then brute
> forced to confirm they are prime/not prime, what % failed?
There's the Agrawal-Kayal-Saxena primality test, but I'm unaware of
any attempts to use it for checking the prime candidates which passed
the Miller-Rabin primality test.
--
Alexey V. Vissarionov aka Gremlin from Kremlin <gremlin ПРИ gremlin ТЧК ru>
GPG: 8832FE9FA791F7968AC96E4E909DAC45EF3B1FA8 @ hkp://keys.gnupg.net
Powered by blists - more mailing lists
Please check out the
Open Source Software Security Wiki, which is counterpart to this
mailing list.
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
