crypt(3X)                                                  crypt(3X)


       NAME
             crypt - password and file encryption functions

       SYNOPSIS
             cc [flag . . . ] file . . . -lcrypt [library] . . .
             #include <crypt.h>
             char *crypt(const char *key, const char *salt);
             void setkey(const char *key);
             void encrypt(char *block, int flag);
             char *des_crypt(const char *key, const char *salt);
             void des_setkey(const char *key);
             void des_encrypt(char *block, int flag);
             int run_setkey(int *connection, const char *key);
             int run_crypt(long offset, char *buffer, unsigned int count,
                   int *connection);
             int crypt_close(int *connection);

       DESCRIPTION
             des_crypt is the password encryption function.  It is based on
             a one-way hashing encryption algorithm with variations
             intended 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 des_setkey and des_encrypt entries provide access to the
             hashing algorithm.  The argument of des_setkey 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 hashing
             algorithm to encrypt the string block with the function
             des_encrypt.

             The argument to the des_encrypt 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


                           Copyright 1994 Novell, Inc.               Page 1

      crypt(3X)                                                  crypt(3X)


            des_setkey.  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.  The international version is part of the C
            Development Set, and the domestic version is part of the
            Encryption Utilities.  If decryption is attempted with the
            international version of des_encrypt, an error message is
            printed.

            crypt, setkey, and encrypt are front-end routines that invoke
            des_crypt, des_setkey, and des_encrypt respectively.

            The routines run_setkey and run_crypt 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.  run_setkey establishes a two-way pipe
            connection with the crypt utility, using key as the password
            argument.  run_crypt takes a block of characters and
            transforms the cleartext or ciphertext into their ciphertext
            or cleartext using the crypt utility.  offset is the relative
            byte position from the beginning of the file that the block of
            text provided in buffer is coming from.  count is the number
            of characters in buffer, and connection is an array containing
            indices to a table of input and output file streams.  When
            encryption is finished, crypt_close is used to terminate the
            connection with the crypt utility.  crypt_close returns -1 if
            it fails to terminate the connection with the crypt utility,
            or a 0 if termination is successful.

            run_setkey returns -1 if a connection with the crypt utility
            cannot be established.  This result will occur in
            international versions of the UNIX system in which the crypt
            utility is not available.  If a null key is passed to
            run_setkey, 0 is returned.  Otherwise, 1 is returned.
            run_crypt 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.

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



                          Copyright 1994 Novell, Inc.               Page 2

       crypt(3X)                                                  crypt(3X)


       REFERENCES
             crypt(1), getpass(3C), login(1), passwd(1), passwd(4)

       NOTICES
             The return value in crypt points to static data that are
             overwritten by each call.










































                           Copyright 1994 Novell, Inc.               Page 3