john-users - Re: checking only first 5 characters of a md5 hash

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Date: Thu, 9 Mar 2006 12:22:14 +0100 (CET)
From: rembrandt@...erlin.de
To: john-users@...ts.openwall.com
Subject: Re: checking only first 5 characters of a md5 hash

> How can I tell John to get the substring of the hash and checking only its
> 5
> chars?
>
> .Thanks.

As far as I know you can`t because for this john would have to know the
keyspace to know where to start and where to end.

Maybe I`m wrong but such a function is not implemented (as far as I know)
but reducing the keyspace by using parts of the key you know or even the
start of the plaintext-password is maybe a neat function... :-)

E.g. if you just saw that xyz entered "At526" at the beginning of the
passwords. Not that we spy passwords.. it`s more to speed up cracking
passwords of users who left. :-))

Kind regards,
Rembrandt