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crypt(3) Library Functions Manual crypt(3) NAME crypt, crypt16, setkey, encrypt - DES encryption SYNOPSIS char *crypt(key, salt) char *key, *salt; char *crypt16(key, salt) char *key, *salt; void setkey(key) char *key; DESCRIPTION The subroutine is the password encryption routine. It is based on the NBS Data Encryption Standard, with variations intended to frustrate use of hardware implementations of the DES for key search. The first argument to is normally a user's typed password. The second is a 2-character string chosen from the set [a-zA-Z0-9./]. The salt string is used to perturb the DES algorithm in one of 4096 different ways, after which the password is used as the key to encrypt repeatedly a constant string. The returned value points to the encrypted pass- word, in the same alphabet as the salt. The first two characters are the salt itself. The subroutine is identical to the function except that it will accept a password up to sixteen characters in length. It generates a longer encrypted password for use with enhanced security features. The other entries provide primitive access to the actual DES algorithm. The argument of is a character array of length 64 containing only the characters with numerical value 0 and 1. If this string is divided into groups of 8, the low-order bit in each group is ignored, leading to a 56-bit key which is set into the machine. The argument to the entry is likewise a character array of length 64 containing 0s and 1s. The argument array is modified in place to a similar array representing the bits of the argument after having been subjected to the DES algorithm using the key set by If edflag is 0, the argument is encrypted; if non-zero, it is decrypted. RESTRICTIONS The return values from and point to static data areas whose content is overwritten by each call. ENVIRONMENT Default Environment In the default environment on systems that do not have the optional en- cryption software installed the function expects exactly one argument, the data to be encrypted. The edflag argument is not supplied and there is no way to decrypt data. If the optional encryption software is in- stalled the function behaves as it does in the POSIX environment. The syntax for the default environment follows: void encrypt(block) char *block; POSIX Environment In the POSIX environment the encrypt function always expects two argu- ments. The function will set errno to ENOSYS and return if edflag is non-zero and the optional encryption software is not present. The syn- tax for the POSIX environment follows: void encrypt(block, edflag) char *block; int edflag; In all cases the function will set errno to ENOSYS and return if the optional encryption software is not present. RELATED INFORMATION login(1), passwd(1), yppasswd(1), getpass(3), passwd(4), prpasswd(4) delim off crypt(3)