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Date: Fri, 2 Oct 2015 08:56:13 +0530
From: Sayantan Datta <>
To: john-dev <>
Subject: Re: GPU-side mask vs. tens of millions of hashes

On Fri, Oct 2, 2015 at 2:28 AM, magnum <> wrote:

> Sayantan,
> I got the idea to test a really large number of hashes with GPU-side mask
> (primarily to stress-test the new FMT_REMOVE code), and it bailed
> ungracefully:
> $ ../run/john -form:raw-md5-opencl -mask:?a -min-len=3
> -max-len=6
> Device 0: GeForce GTX TITAN X
> Loaded 24917564 password hashes with no different salts (Raw-MD5-opencl
> [MD5 OpenCL])
> 128 bit add overflow.
> Is this an expected outcome, or is 25 million hashes supposed to work
> fine? If it's not supposed to work, what is the design maximum? Perhaps we
> can bail out with a bit more finesse, eg. telling the user a max.?
> oclHashcat supports "up to 100 million hashes". I'm not sure we need to
> support that, but it wouldn't hurt.
> magnum
This is an issue with table building. I'll fix. 25 million shouldn't be
much of an issue. In fact, I had 100-120 million hashes in mind when
writing tables algorithm, and I tested it for 110 million 128bit hashes and
upto 60 million 192 bit hashes. However, as solar said, some adjustments
are required regarding initial table size.


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