1CRYPT(3) Library Functions Manual CRYPT(3)
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6 crypt, setkey, encrypt - DES encryption
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9 char *crypt(key, salt)
10 char *key, *salt;
11 setkey(key)
13 char *key;
14 encrypt(block, edflag)
16 char *block;
17
19 Crypt is the password encryption routine. It is based on the NBS Data
20 Encryption Standard, with variations intended (among other things) to
21 frustrate use of hardware implementations of the DES for key search.
22 The first argument to crypt is normally a user's typed password. The
24 second is a 2-character string chosen from the set [a-zA-Z0-9./]. The
25 salt string is used to perturb the DES algorithm in one of 4096 differ‐
26 ent ways, after which the password is used as the key to encrypt
27 repeatedly a constant string. The returned value points to the
28 encrypted password, in the same alphabet as the salt. The first two
29 characters are the salt itself.
30 The other entries provide (rather primitive) access to the actual DES
32 algorithm. The argument of setkey is a character array of length 64
33 containing only the characters with numerical value 0 and 1. If this
34 string is divided into groups of 8, the low-order bit in each group is
35 ignored, leading to a 56-bit key which is set into the machine.
36 The argument to the encrypt entry is likewise a character array of
38 length 64 containing 0's and 1's. The argument array is modified in
39 place to a similar array representing the bits of the argument after
40 having been subjected to the DES algorithm using the key set by setkey.
41 The edflag flag is ignored; the argument can only be encrypted.
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44 passwd(1), passwd(5), login(1), getpass(3)
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47 The return value points to static data whose content is overwritten by
48 each call.
497th Edition August 12, 1986 CRYPT(3)