CrackLib is a library containing a C function (well, lots of functions
really, but you only need to use one of them) which may be used in a
"passwd"-like program.
The idea is simple: try to prevent users from choosing passwords that
could be guessed by "Crack" by filtering them out, at source.
CrackLib finds potential passwords quickly, by using an index file to
access dictionary words, and by keeping a table to assist binary
searching.
CrackLib's dictionary is modified-DAWG compressed with a chunksize of 16
words and then the index file is built, with one entry per chunk.
CrackLib makes literally hundreds of tests to determine whether you've
chosen a bad password.
* It tries to generate words from your username and gecos entry to tries
to match them against what you've chosen.
* It checks for simplistic patterns.
* It then tries to reverse-engineer your password into a dictionary
word, and searches for it in your dictionary.
- after all that, it's PROBABLY a safe(-ish) password.
