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Date: Fri, 20 Jul 2012 20:39:04 +0200
From: Frank Dittrich <frank_dittrich@...mail.com>
To: john-dev@...ts.openwall.com
Subject: Re: Some more external mode definitions

On 07/20/2012 08:06 PM, Solar Designer wrote:
> On Fri, Jul 20, 2012 at 07:27:00PM +0200, Frank Dittrich wrote:
>> The first patch creates new [List.External:Repeats_*] sections, similar
>> to [List.External:Repeats], but with a limited character set.
>> Repeats_digits: '0' - '9'
>> Repeats_lowercase: 'a' - 'z'
>> Repeats_printable_ASCII: ' ' - '~'
>> The common logic has been moved into [List.External_base:Repeats].
> 
> I don't mind, but I felt that Repeats was quick enough as it was, except
> maybe for very slow hashes/ciphers - but in those rare cases you'd
> probably want to reduce the length first / as well.

I just thought that printable characters are more likely, and it saves
more than 50% of the run time. I intended to use it for slow hashes.
The maximum length is not that much of a problem for me, because for
slow hashes, I intend to interrupt the session when the length has
reached the maximum supported length of the format (e.g., 27 for mscash2).
BTW: I should try to write a patch which makes the max. password length
(for the format, or specified using --stdout=LENGTH) available in
external modes.
Then, the external mode could stop if the length exceeds the max. length.

Without these new external modes, you could also use --stdout and grep
for the characters you want to include / exclude, and use a word list
file instead.
This would even have the advantage to use just the missing characters in
a repeated run, whereas with the external mode, you'd have to use all
the characters from ' ' to 0xff.

So may be it really isn't worth adding these external modes.

>> The second patch adds a simple Rot13 filter, [List.External:Filter_Rot13].
>> Words that don't contain any letters (and would remain unchanged after
>> applying rot13) are skipped (word = 0).
> 
> Please document this detail in a comment.

OK, new patch attached instead of the old one.
(For me it would be obvious to skip unchanged words which probably
should have been tried before trying mangled words.)

Frank

View attachment "0001-Add-List.External-Filter_Rot13.patch" of type "text/x-patch" (1192 bytes)

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