CRYPT(3X-SysV)      RISC/os Reference Manual       CRYPT(3X-SysV)



NAME
     crypt - password and file encryption functions

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

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

     void setkey (key)
     char *key;

     void encrypt (block, flag)
     char *block;
     int flag;

     char *des_crypt (key, salt)
     char *key, *salt;

     void des_setkey (key)
     char *key;

     void des_encrypt (block, flag)
     char *block;
     int flag;

     int run_setkey (p, key)
     int p[2];
     char *key;

     int run_crypt (offset, buffer, count, p)
     long offset;
     char *buffer;
     unsigned int count;
     int p[2];

     int crypt_close(p)
     int p[2];

DESCRIPTION
     des_crypt 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 dif-
     ferent 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.



                         Printed 1/15/91                   Page 1

CRYPT(3X-SysV)      RISC/os Reference Manual       CRYPT(3X-SysV)



     The des_setkey and des_encrypt entries provide (rather prim-
     itive) access to the actual 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; this gives a 56-bit key which is set
     into the machine.  This 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 des_setkey.  If edflag 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 Programming Language Utilities, and the domestic ver-
     sion is part of the Security Administration 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 crypt(1), 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 crypt(1). offset is the relative byte
     position from the beginning of the file that the block of
     text provided in block is coming from.  count is the number
     of characters in block, and connection is an array contain-
     ing indices to a table of input and output file streams.
     When encryption is finished, crypt_close is used to ter-
     minate the connection with crypt(1).

     run_setkey returns -1 if a connection with crypt(1) cannot
     be established.  This will occur on international versions
     of UNIX where crypt(1) 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.





 Page 2                  Printed 1/15/91

CRYPT(3X-SysV)      RISC/os Reference Manual       CRYPT(3X-SysV)



DIAGNOSTICS
     In the international version of crypt(3X), a flag argument
     of 1 to des_encrypt is not accepted, and an error message is
     printed.

SEE ALSO
     getpass(3C), passwd(4).
     crypt(1), login(1), passwd(1) in the User's Reference
     Manual.

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










































                         Printed 1/15/91                   Page 3