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Date: Mon, 28 May 2012 00:29:25 +0200
From: Frank Dittrich <>
Subject: Re: UI for MJohn

On 05/27/2012 02:16 PM, Aleksey Cherepanov wrote:
> For instance user looks into web ui, find successful attack that
> covers only part of hashes (how?)

Did you want to ask how it can be possible that an attack covered only
part of the hashes of a particular hash type (format)?.

If so, there can be several reasons, e.g.:

You have so many different hashes that they don't fit into the RAM,
would you try to load them all at the same time.
So you would just split all these hashes into several files, and start
cracking the hashes in one of those files.
The attacks that turn out to be most effective on this first file will
then be tries on the other files.

You have a large number of salted hashes, but you notice that the hashes
are not distributed randomly across the possible salts.
Some salts have much more hashes than others.
So it might make sense to split the hashes into different files,
depending on the number of hashes per salt.
You start cracking the hashes of the file with many different hashes per
salt, because you'll be able to crack more passwords by computing fewer
hashes (and doing more comparisons of hashes - which sould be faster
than computing hashes).
The most effective attacks are then tried against the other file(s) with
a smaller number of different hashes per salt.

You have a salted hash format, and an even distribution of hashes (say
just one hash per salt), but you know some of the users are more
privileged than others.
So you try to spend more effort trying to crack the hashes of those more
valuable accounts first, later on you might want to try these attacks on
less important accounts.


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