crypt(3X)                                                         crypt(3X)

NAME
     crypt, setkey, encrypt, descrypt, dessetkey, desencrypt,
     runsetkey, runcrypt, cryptclose - password and file encryption
     functions

SYNOPSIS
     cc [flag ...] file ... -lcrypt

     #include <crypt.h>

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

     void setkey(const char *key);

     void encrypt(char *block, int flag);

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

     void dessetkey(const char *key);

     void desencrypt(char *block, int flag);

     int runsetkey(int *p, const char *key);

     int runcrypt(long offset, char *buffer, unsigned int count,
                    int *p);

     int cryptclose(int *p);

DESCRIPTION
     descrypt() is the password encryption function. It is based on a
     one-way hashing encryption algorithm with variations intended (among
     other things) to frustrate use of hardware implementations of a key
     search.

     key is a user's typed password. salt is a two-character string chosen
     from the set [a-zA-Z0-9./]; this string is used to perturb the hashing
     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 password. The first two characters are
     the salt itself.

     The dessetkey() and desencrypt() functions provide access to the
     actual hashing algorithm. The argument of dessetkey() 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, thereby creating a 56-bit key that is set
     into the machine. This key is the key that will be used with the hash-
     ing algorithm to encrypt the string block with the function
     desencrypt().





Page 1                       Reliant UNIX 5.44                Printed 11/98

crypt(3X)                                                         crypt(3X)

     The argument to the desencrypt() entry is a character array of length
     64 containing only the characters with numerical value 0 and 1. The
     argument array is modified in place to a similar array representing
     the bits of the argument after having been subjected to the hashing
     algorithm using the key set by dessetkey(). If flag is zero, the
     argument is encrypted; if non-zero, it is decrypted.

     Note that decryption is not provided in the international version of
     crypt(3X). The international version is part of the C Development Set,
     and the domestic version is part of the Security Administration Utili-
     ties. If decryption is attempted with the international version of
     desencrypt(), an error message is printed.

     crypt(), setkey(), and encrypt() are front-end routines that invoke
     descrypt(), dessetkey(), and desencrypt() respectively.

     The routines runsetkey() and runcrypt() are designed for use by
     applications that need cryptographic capabilities [such as ed(1) and
     vi(1)] that must be compatible with the crypt(1) user-level utility.
     runsetkey() establishes a two-way pipe connection with the crypt()
     utility, using key as the password argument. runcrypt() takes a block
     of characters and transforms the cleartext or ciphertext into their
     ciphertext or cleartext using the crypt() utility. offset is the rela-
     tive byte position from the beginning of the file that the block of
     text provided in buffer is coming from. count is the number of charac-
     ters in buffer, and p is an array containing indices to a table of
     input and output file streams. When encryption is finished,
     cryptclose() is used to terminate the connection with the crypt(1)
     utility.

     runsetkey() returns -1 if a connection with the crypt(1) utility can-
     not be established. This result will occur in international versions
     of the Reliant UNIX system in which the crypt(1) utility is not avail-
     able. If a null key is passed to runsetkey(), 0 is returned; other-
     wise, 1 is returned. runcrypt() returns -1 if it cannot write output
     or read input from the pipe attached to crypt(). Otherwise it returns
     0.

     The program must be linked with the object file access routine library
     libcrypt.a.

RESULT
     In the international version of crypt(3X), a flag argument of 1 to
     encrypt() or desencrypt() is not accepted, and errno is set to ENOSYS
     to indicate that the functionality is not available.

NOTES
     The return value in crypt() points to static data that is overwritten
     by each call.

SEE ALSO
     crypt(1), login(1), passwd(1), getpass(3C), passwd(4).


Page 2                       Reliant UNIX 5.44                Printed 11/98