crypt(3)						     Library Functions Manual							  crypt(3)

NAME

       crypt, crypt16, setkey, encrypt - DES encryption

SYNOPSIS

       #include <unistd.h>
       #include <stdlib.h>

       char *crypt(
	    const char *key,
	    const char *salt);

       char *crypt16(
	    const char *key,
	    const char *salt);

       void setkey(
	    const 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 repeat-
       edly a constant string.	The returned value points to the encrypted password, 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, lead-
       ing 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 encryption software installed the function expects  exactly	one  argu-
       ment,  the data to be encrypted. The edflag argument is not supplied and there is no way to decrypt data.  If the optional encryption soft-
       ware is installed 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 arguments.  The function will set errno to ENOSYS and return if edflag	is
       non-zero and the optional encryption software is not present.  The syntax 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)