Programmable Dictionary Generator
While traditional password cracking tools simply fed a pre-existing dictionary of words through the crypt function Crack v4.0a introduced the ability to apply rules to this word list to generate modified versions of these word lists.
These could range from the simple (do not change) to the extremely complex - the documentation gives this as an example:
- X<8l/i/olsi1so0$=
- Reject the word unless it is less than 8 characters long, lowercase the word, reject it if it does not contain both the letter 'i' and the letter 'o', substitute all i's for 1's, substitute all o's for 0's, and append an = sign.
These rules could also process the GECOS field in the password file, allowing the program to use the stored names of the users in addition to the existing word lists. Crack's dictionary generation rule syntax was subsequently borrowed and extended by Solar Designer for John the Ripper.
The dictionary generation software for Crack was subsequently reused by Muffett to create CrackLib, a proactive password checking library that is bundled with Debian and Red Hat Enterprise Linux-derived Linux distributions.
Read more about this topic: Crack (password Software)
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