[suse-security] passwords

Subject: [suse-security] passwords
From: willy (willyph-karlsruhe.de)
Date: Mon Jan 31 2000 - 00:34:08 CST

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Hi,

the UNIX/Linux password encoding mechanism is a derivation of DES, which uses
a 56-bit encoding key (eight 7-bit characters).

I.e. the crypt() function takes the user's password, pads it out to 8 (!)
characters, and then uses 7 bits of each character to form a 56-bit DES key.
This key is used to encrypt a 64-bit block of zeros, ...

The final output is a string of 11 characters.

A "salt" 2-character string is added to the first string.

Thus, a complete encoded password entry consists of 13 characters.
(see the second field in /etc/shadow)

With Extended crypt the plaintext password can be longer than 8 characters;

best regards

willy

-- 
Willy Luchian 
Paedagogische Hochschule
ZIM - System- u. Netzadministration 
Bismarckstrasse 10; D-76133 Karlsruhe/Germany
willyph-karlsruhe.de  phone: +49-721-9254744
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