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Date: Tue, 13 Aug 2013 15:29:12 +1000
From: Michael Samuel <>
Subject: Re: key-length for mask mode.

On 13 August 2013 15:10, Sayantan Datta <> wrote:

> More optimizations are possible if we could limit the key length to 16.
> Current key length limit of 55 seems to be unnecessary. This should free up
> some more registers and allow me to introduce few more bitmpas.
> I was doing some of my own playing with this kernel, and was thinking it
would be better to pass a complete block (already padded), with these

- Only pass 15 integers, X[15] is always zero for single blocks, so pass it
as a constant
- Align X column-wise, eg X[(gsize*n)+gid].  This will make the kernel work
on AVX nicely, and also helped heaps on my old nVidia GTX-9800. (I don't
have a modern GPU that does OpenCL at the moment)

Hard-coding other parts of X[] works too (which is what I assume you're
doing) - for otp-md5 I created a kernel that passed X0 and X1 via global
mem, then hardcoded the rest of the array, but that's because it was always
8 bytes of input.

I haven't delved into the JtR source yet to see how easy this is to do, I
was mostly just interested because I wanted to hear how well the Phi worked


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