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Date: Mon, 3 Jul 2017 21:25:42 +0200
From: Solar Designer <>
Cc: Denis Burykin <>
Subject: Re: bcrypt cracking on ZTEX 1.15y FPGA boards (bcrypt-ztex)

On Mon, Jul 03, 2017 at 07:14:01PM +0200, Solar Designer wrote:
> On Mon, Jul 03, 2017 at 07:12:12AM -0800, Royce Williams wrote:
> > 0:00:00:00 - Candidate passwords will be buffered and tried in chunks of 262140
> > 
> > ... for values of both 5 and 6 for TargetSetting.
> Yes, in your case TargetSetting shouldn't matter, because you have so
> many boards that the value is capped anyway.  But you could try hacking
> this cap in the source, in ztex_bcrypt.c:
>         262140, // Absolute max. keys/crypt_all_interval for all devices.
> Try setting it to 2031616 (as 63488*32), and then TargetSetting will be
> making a difference.
> Denis - by the way, 262140 isn't even a multiple of 496 (core count per
> board) - perhaps that's wrong and should be fixed.

Royce, Denis has just explained to me where this value comes from, and
it's correct as-is and isn't to be patched: things are not expected to
work correctly for higher values.  So please disregard this part of my
advice.  Denis intends to remove this limitation in a future revision.


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