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Message-ID: <5022DBC4.5030403@semjanov.com>
Date: Thu, 09 Aug 2012 01:36:04 +0400
From: Pavel Semjanov <pavel@...janov.com>
To: john-dev@...ts.openwall.com
Subject: Re: Patch for pkzip_fmt_plug.c from jumbo-6
> Both of the files are plain archives without encryption. Maybe you sent
> the wrong ones?
I've just explained why I can't to it in previous message.
>
>>> BTW, could you by any chance help us with better early rejection
>>> in the RAR format? I'm just asking :)
>>
>> It's quite simple. In CPU code, the block is checked for LZ type or
>> PPM type. If it's LZ, the Huffman table test is used, like ZIP does.
>
> Thanks! So I can pre-test it more or less exactly like pkzip do? I
> thought there would be differences between LZ2 and LZ. Does cRARk do
> this fairly similar to Jim's pkzip code?
Any codes for Huffman table check are fairly similar ;)
>
> Regardless, I think I'll need Jim's help here.
>
>> If it's PPM, the reset bit should be set and MaxMB size can't be
>> grather than 7f. If yes, the decompression begins and password is
>> rejected quite fast in RAR PPM code.
>
> OK. So that is what, 9 bits in total? Then I can reject 75% [of PPM]
> without even calling rar_unpack29(), right?
Hmm... 3 bits, right? One for PPM, one for reset, one for MaxMB. So, 7/8
of passwords can be rejected.
>
>> In GPU code, only standard parameters (i.e, -m0 .. -m5) are allowed.
>> This makes very effective early reject by checking MaxOrder and MaxMB
>> sizes.
>
> I suppose I should transfer a portion of the file to GPU so I can reject
> immediately. Hm, but then I'd need to implement AES on GPU too.
OpenSSL code (which is very similar to original optimized code) runs
fine of CUDA and OpenCL.
I am
> very impressed with how cRARk is totally immune against file size. But
> I'll try to implement this without changing my Key-derivation-only
> kernel, as a first step.
>
> I'll try this soon, lots of thanks!
>
> magnum
>
>
--
SY / C4acT/\uBo Pavel Semjanov
_ _ _ http://www.semjanov.com
| | |-| |_|_| |-|
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