UFC-crypt or how my code ended up in your Linux box
Back in the dark ages, I read the papers analyzing the “Morris Internet Worm”. In order to protect my employers systems, I wanted to do proactive password cracking.
This, however, was painfully slow. A SUN 3⁄50 could do some 5 password checks a second. This was because the Crypt(3) function does 25 slightly modified DES encryptions using the supplied password as the encryption key.
The number 25 had been chosen to make things slow on the machines available back then.