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Date: Wed, 17 Sep 2014 00:58:29 +0200
From: magnum <>
Subject: Re: attacking RC2 40-bit S/MIME encrypted emails

On 2014-09-17 00:00, magnum wrote:
> On 2014-09-16 22:44, augustin wrote:
>>>> long time ago, Bruce Schneier published a tool for Windows 95 to
>>>> attack S/MIME encrypted emails that use RC2 for encryption with
>>>> 40bit long keys.
>>>> code:
>>>> I had a look at john formats but did not find anything related.
>>>> Does john support that type of encryption or will it be supported
>>>> in the future?
>>> It doesn't, and I doubt anyone was planning to write it. Is RC2/40
>>> still used at all anywhere?
>> 'openssl smime -encrypt' uses RC2/40 by default according to
>> documentation.
>> fedora 20 (openssl-1.0.1e-39)/ubuntu 14.04/rhel 6.4:
>>     man smime: "If not specified 40 bit RC2 is used."
>> so an implementation would probably still be useful these days.
> Cool. Someone should do this.

It now hits me this is out of scope for JtR itself. What JtR does is 
always based on trying human-like passwords. But this "format" would be 
a key brute-forcer with no input. For the same reason, we haven't 
implemented an RC4/40 brute-forcer for old Office documents.

However, even if Solar doesn't want these "in" Jumbo, I'm willing to 
include them either "with" Jumbo (as stand-alone programs in the Jumbo 
source tree), or simply as a separate repo if Solar persists. As Atom 
recently wrote on Hashcat forum, you can sometimes marry RC4-BF with 
actual password search:


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