CRYPT(3)						     Library Functions Manual							  CRYPT(3)

NAME

       crypt - one-way password encryption function

SYNOPSIS

       #define _MINIX_SOURCE 1
       #include <unistd.h>

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

DESCRIPTION

       The  first  use	of  crypt()  is  to encrypt a password.  Its second use is to authenticate a shadow password.  In both cases crypt() calls
       pwdauth(8) to do the real work.

       Crypt() encrypts a password if called with a user typed key, and a salt whose first two characters  are	in  the  set  [./0-9A-Za-z].   The
       result  is  a  character  string in the [./0-9A-Za-z] alphabet of which the first two characters are equal to the salt, and the rest is the
       result of encrypting the key and the salt.

       If crypt() is called with a salt that has the form ##user then the key is encrypted and compared to the encrypted password of user  in  the
       shadow  password  file.	If they are equal then crypt() returns the ##user argument, if not then some other string is returned.	This trick
       assures that the normal way to authenticate a password still works:

	      if (strcmp(pw->pw_passwd, crypt(key, pw->pw_passwd))) ...

       If key is a null string, and the shadow password is a null string or the salt is a null string then  the  result  equals  salt.	 (This	is
       because the caller can't tell if a password field is empty in the shadow password file.)

       The key and salt are limited to 1024 bytes total including the null bytes.

FILES

       /usr/lib/pwdauth 	The password authentication program

SEE ALSO

       getpass(3), getpwent(3), passwd(5), pwdauth(8).

NOTES

       The result of an encryption is returned in a static array that is overwritten by each call.  The return value should not be modified.

AUTHOR

       Kees J. Bot (kjb@cs.vu.nl)

																	  CRYPT(3)