Date: Wed, 24 Jul 2013 04:28:33 +0400 From: Solar Designer <solar@...nwall.com> To: john-dev@...ts.openwall.com Subject: Re: Katja's weekly report #6 Hi Katja, On Mon, Jul 22, 2013 at 11:59:43PM +0200, Katja Malvoni wrote: > Accomplishments: > 1. Integration with JtR finished Cool. Just how confident are we that it's working reliably, though? Yes, the 2-hour run has succeeded, but if e.g. one in 10k hashes were not computed/transferred correctly then chances are that this would not be noticed in a run that is only supposed to get 3k passwords cracked. My concern is that, if I understood Yaniv correctly, the data transfers to/from Epiphany do not have to complete in-order, yet your code relies on the flags being seen strictly before/after the data. Maybe you can test similar data transfers in a dummy application that would do very little computation (so it'd spend most of its time on the transfers back and forth), but would instead deliberately try to detect cases of out-of-order arrival? In a password cracker, we'd only detect false negatives (a correct password not resulting in the hash getting cracked) and false positives (very unlikely: if a wrong password somehow happens to result in the correct hash value, e.g. if two computed hash values somehow got swapped in transfer). The problem is that we won't detect cases where a false negative is the correct outcome (this is true most of the time!), yet the computed hash value is different from what it should be. So we don't actually test whether most of the computed hash values are correct - we only test a small minority of them. This is why I suggest that you implement an actual stress-test, where any data transfer error would be detected (unlike in a password cracker, where most would go undetected). > Priorities: > 1. Optimize Epiphany bcrypt implementation > 2. Start with bcrypt implementation on FPGA Yes, please - and please keep john-dev aware of your progress (more often than weekly, in addition to the weekly reports). Thanks, Alexander
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