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Date: Sun, 19 Jul 2015 13:56:12 +0300
From: Aleksey Cherepanov <>
Subject: multiformats, (ab)use of salt in 'gost' format

Recently I discovered that 'gost' format has salt. Using it, it
differentiates regular gost and cryptpro gost. These can be viewed as
2 formats with 1 algo and different sboxes. There are 2 format tags:

#define FORMAT_TAG		"$gost$"
#define FORMAT_TAG_CP		"$gost-cp$"

So the 'salt' shows sboxes to use.

It can be generalized to multiformats: such formats that handle hashes
of different formats as 1 format (even without any similarities
between algorithms).

Multiformats may be interesting during contests to attack all fast
hashes in 1 command (the idea is not mine, Solar Designer shared this
idea after last hash runner). It would be something like --format=fast

Solar Designer pointed out to me that formats can assume that, when
their init() is called, other formats are done(), so 2 formats can't
be init()'ed in parallel.

Another approach to multiformats would be a wrapper that calls john
several times.

Other ideas?


Aleksey Cherepanov

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