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Date: Sat, 19 Sep 2015 12:52:39 +0200
From: magnum <john.magnum@...hmail.com>
To: john-dev@...ts.openwall.com
Subject: Re: fast hash early exit vs. large hash list

On 19/09/15 11:17, Aleksey Cherepanov wrote:
> On Sat, Sep 19, 2015 at 02:33:21AM +0200, magnum wrote:
>> On 18/09/15 17:25, Solar Designer wrote:
>>> For raw-md5, we currently have early exit before the last 3 steps.
>>> Aside from this being extremely far from what state of the art fast
>>> hash crackers do in terms of steps reversal,
>>
>> Can we reverse any more without considering the actual candidate (or its
>> length)? I doubt the shared functions are suitable for hard-core reversal.
>> It might be better to do so in formats like the -ng ones that doesn't use
>> shared code. Or at least do them first.
>
> Just some formulas for you convenience:

> Reversed algo for last round ([abcd]64 consist hash, [abcd]63 are for
> previous state):
>
> i = 63
> b63 = c64
> c63 = d64
> d63 = a64
> g = 9
> a63 = ror(b64 - c64, s[i]) - (d64 ^ (c64 | (~a64)) + k[i] + m[g])
>
> So, not considering candidate (m), we know b63, c63, d63.
 > (...)

> Check against millions of hashes may just need 2 ints, not fully
> stored state.

This is an important fact, didn't think of that. But it's more branching.

Thanks!
magnum

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