Date: Tue, 20 Oct 2015 10:22:40 -0600 From: Kurt Seifried <kseifried@...hat.com> To: oss-security <oss-security@...ts.openwall.com> Subject: Re: Prime example of a can of worms So some new questions arise: 1) in openssl does the -2/-5 option matter with respect to security? I read http://security.stackexchange.com/questions/54359/what-is-the-difference-between-diffie-hellman-generator-2-and-5 and some other things and I have no idea if there is a real impact on security. I bet the other tools have similar switches for which very few people seem to understand what they actually do, and if they actually impact security meaningfully. 2) Openssl/gnutls (and likely others) all apparently have slight variations on how they generate/test primes. E.g. http://nmav.gnutls.org/2011/12/generating-diffie-hellman-parameters.html this worries me, diversity is good, but if not implemented correctly. Do any best practices actually exist? 3) in testing for primeness how sure are we? Reading https://en.wikipedia.org/wiki/Miller%E2%80%93Rabin_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? -- Kurt Seifried -- Red Hat -- Product Security -- Cloud PGP A90B F995 7350 148F 66BF 7554 160D 4553 5E26 7993 Red Hat Product Security contact: secalert@...hat.com
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