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Date: Sat, 20 Oct 2012 15:23:24 +0530
From: Dhiru Kholia <dhiru.kholia@...il.com>
To: john-dev@...ts.openwall.com
Subject: Re: cracking 40-bit RC4 keys of Office and PDF files

On Thu, Oct 18, 2012 at 1:23 PM, Dhiru Kholia <dhiru.kholia@...il.com> wrote:
> On Thu, Oct 18, 2012 at 10:34 AM, Solar Designer <solar@...nwall.com> wrote:
>> On Thu, Oct 18, 2012 at 10:22:29AM +0530, Dhiru Kholia wrote:
>> Huh?  GuaPDF cracks these in about the same time that GuaWord/GuaExcel
>> do, so I think that you're wrong.  Perhaps the MD5s are inside the loop
>> only when you're cracking passwords and not keys?
>
> My bad. You are right.

Update: brute-forcing RC4 keyspace for PDF files is a *lot* faster
than Office files since it doesn't involve extra MD5 step.

I have modified qpdf to do decryption using RC4 key. See
https://github.com/kholia/qpdf.git

Now all we need are some kind of Rainbow Tables to make cracking faster.

-- 
Cheers,
Dhiru

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