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Date: Fri, 21 Aug 2015 11:03:19 +0800
From: Kai Zhao <loverszhao@...il.com>
To: john-dev@...ts.openwall.com
Subject: Re: BENCHMARK_LENGTH bugs
On Fri, Aug 21, 2015 at 10:31 AM, Solar Designer <solar@...nwall.com> wrote:
> Kai,
>
> On Fri, Aug 21, 2015 at 09:45:21AM +0800, Kai Zhao wrote:
>> The speed of dominosec8 is 3471 c/s, and the speed of 7z is 3056 c/s.
>> The 3471 c/s and 3056 c/s is not very slow ? There are about 16
>> formats whose speed is small than 3056 c/s ? What speed can be
>> recognized as "slow" ?
>
> This is irrelevant, because:
>
>> If I understand "slow" correctly, then the difference between
>> "Only one salt" and "Many salts" has nothing to do with "slow" ?
>
> There's correlation, but not more than that.
>
> I only mentioned "slow" as the typical case where we'd often avoid
> running two benchmarks, but clearly there are exceptions like these two,
> where we'd want to run separate "Only one salt" and "Many salts"
> benchmarks anyway.
>
> Extra detail, which is probably overkill for you:
>
> In terms of code, what matters is whether there's significant processing
> done per candidate password yet shared for all salts. We do this in
> set_key(). If all max_keys_per_crypt calls to set_key() combined are
> e.g. 1000 times quicker than crypt_all(), then we likely don't want to
> run separate "Only one salt" and "Many salts" benchmarks. (And indeed
> we also won't if the hash is unsalted, regardless of how fast or slow
> its set_key() is.) However, there are exceptions to this: sometimes
> would-be-set_key()'s expensive processing is postponed until
> crypt_all() (e.g., in order to put it inside an OpenMP parallel region),
> yet is effectively only done per key (and is skipped on further
> crypt_all() calls).
>
Thanks for the detailed reply. This does overkill for me. Could we define
slow: whose speed is less than e.g. 1000K c/s ?
Below is my current understand for the benchmark_length's checking.
benchmark_length salt_size speed warning/error exceptions
------------------------------------------------------------------------------------------------
0 0 slow/fast error no
------------------------------------------------------------------------------------------------
0 !0 slow warning yes (such as
dominosec8 and 7z)
------------------------------------------------------------------------------------------------
0 !0 fast ok no
------------------------------------------------------------------------------------------------
-1 0 slow/fast ok no
------------------------------------------------------------------------------------------------
-1 !0 slow ok yes (to be add)
------------------------------------------------------------------------------------------------
-1 !0 fast warning yes (to be add)
------------------------------------------------------------------------------------------------
Thanks,
Kai
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