password cracking : - DES can only be cracked by a brute force attack, because there is no way to crack the s-boxes. - to crack DES, means to find the 56 bit long key. - the cracker has 2^56 different keys, and only one is the right - he has the encrypted password, the algorithm and the way to encrypt passwords, then he tests all 2^56 different keys and compares it with the value of the shadow-file, one key shows the cleartext password
There's a misconception here. People seem to believe that some magic key is used to encrypt the password. This is wrong. It's not the password that gets encrypted. The password is used to encrypt the salt (the two characters the come first in the password field in /etc/shadow). So the key _is_ the password - and there are much more efficient ways to brute forcing passwords using e.g. dictionary attacks. Check out john the ripper (there's a suse package for it called john I think). Choosing a good password hashing algorithm isn't just a question of key size. It's a question of speed, too. Fast algorithms are bad. Slow algorithms are better. Olaf -- Olaf Kirch | Anyone who has had to work with X.509 has probably okir@suse.de | experienced what can best be described as ---------------+ ISO water torture. -- Peter Gutmann