🚀 go-pugleaf

In comp.security.unix Raphael <rraphael_pierre@hotmail.com> wrote:
> It was stated that the inclusion of the salt in the UNIX password scheme
> increases the difficulty of guessing by a factor of 4096.  But the salt
> may be stored in plaintext in the same entry as the corresponding
> ciphertext password. Therefore, those two characters may be known to the
> attacker and need not be guessed.  Why then is it asserted that the salt
> increases security?

The two salt characters are prepended to the password prior to
encryption. This has a couple advantages:

1. It discorages building a code book by requaring you to
store 4096 entries for each possibible password.

2. It also prevents identical passwords from generating identical
entries in /etc/password. For each guess, you need to do a crypt(3)
for every salt which appears in the password file. crypt(3) being the
most time consuming part of the process by far, salt really slows
things down.

There are a couple other minor bonuses from salt, but no show
stoppers. In short, it makes breaking arbitrary passwords harder. For
brute forcing a single entry, it's "only" as hard as breaking DES. 

-- 
Matthew Gauthier <elleron@crosswinds.net>