Date: Wed, 28 Sep 2011 09:53:12 +0200 From: magnum <rawsmooth@...dband.net> To: john-dev@...ts.openwall.com Subject: Re: Some ideas about enhanced self-test On 2011-09-27 16:12, jfoug wrote: >> From: David Jones [mailto:jonesd@...umbus.rr.com] >> On Sep 27, 2011, at 2:29 AM, magnum wrote: >>> I take this on-list from here in case someone wants to chime in. This >>> started as a private discussion about eg. crc-32 and dummy getting >>> significantly inflated benchmark figures [from testing null-string] >> >> On first blush, I'd suggest having a field bench_weight whose value >> reflects the relative frequency that's to be tested during benchmarking. >> A zero value is used for edge cases that very rare but need to be >> included in the self test for completeness. An 8 character password >> would be given a higher weight than the 20 character test password if >> that's relevant to the benchmark. ... > Now one way to proceed is to somehow build the list of words to use, prior > to actually 'entering' the loop the feeds the format benchmarking it. If > done this way we 'could' do frequency percentages, by building a pseudo > wordlist during benchmarking, and adding words in proper proportion, then > spinning through that list. At benchmark time (the inner loop), we would > not have to compute percentages. They have been done 1 time, prior to > startup. I think that's too much code for little gain. Jim, what if you include the nullstring in crc-32 but also include a max-length string? Would that push the benchmarks back closer to real-life figures, or would it push it back too far? For that matter, bench.c could (during test phase) construct a max-length string consisting of random ascii or just a repeated character, and set that as key at every other index up to max_keys_per_crypt, using valid strings inbetween (which of course are expected to pass). This should catch many buffer overruns. magnum
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