Date: Fri, 1 Feb 2013 21:22:51 +0400 From: Solar Designer <solar@...nwall.com> To: john-dev@...ts.openwall.com Subject: Re: NTLMv1 and MSCHAPv2 (was: NetNTLMv1) On Fri, Feb 01, 2013 at 05:58:44PM +0100, magnum wrote: > Fixed. I have also merged the same exploit and SIMD code to MSCHAPv2. That format is very similar - in JtR all main functions are identical except get_salt() so this was very wasy. Actually we should wrap them in the same source file so we don't need to incorporate the same optimizations to both formats in the future. Cool. I think a similar trick may be possible for NetLM as well - in fact, I think that's what mudge's examples from the 1997 posting found by Alexander were about. I just don't have time and desire to look into it myself now - but you may. ;-) Here's a concern about these optimizations, though: they slow down the loading, which may be nasty if someone is cracking a very large number of C/R pairs at once. I think the 32k DES encryptions with OpenSSL's code on one CPU core may be taking about 10 ms, which means a loading speed of 100 C/R pairs per second. With 1 million to load, that's 3 hours. Is it realistic that someone will have this many? Should we possibly print a warning when we determine that the number of C/R pairs is 100 or larger? Should we provide an alternative mode - like the code we had before? some way to invoke John to crack the 3rd DES blocks only and record the 16-bit results for reuse by subsequent invocations? Another concern: when the number of responses per challenge is very large, these optimizations may actually be slowing things down, because we're no longer providing hash functions with larger than 16-bit output. Is it realistic that someone would have millions of responses for the same challenge? Perhaps if a fixed challenge is provided in an active attack? I think the typical case is having only a relatively small number of C/R pairs, though. If so, our changes speed things up a lot. Alexander
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