CRYPT(3X)        MISCELLANEOUS LIBRARY FUNCTIONS        CRYPT(3X)


NAME
     crypt -- password and file encryption functions


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

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

     void setkey(char *key);

     void encrypt(char *block, int flag);

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

     void des_setkey(char *key);

     void des_encrypt(char *block, int flag);

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

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

     int crypt_close(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 alter the hashing
     algorithm in one of 4096 different  ways,  after  which  the
     password is used as the key to repeatedly encrypt 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 (rather prim-
     itive)  access  to  the  actual   hashing   algorithm.   The
     des_setkey  argument  is  a  character  array  of 64 bits in
     length containing only characters with a numerical value  of
     0  and  1.  If  this string is divided into groups of 8, the
     low-order bit in each group  is  ignored;  this  produces  a
     56-bit  key  that is set into the machine.  This key is used
     with the hashing algorithm to encrypt the string block  with
     the des_encrypt function.

     The  argument  to the des_encrypt entry is a character array
     of 64 bits in  length  containing  only  characters  with  a
     numerical  value  of 0 and 1. The argument array is modified



SUPER-UX            Last change: Oct  3, 1997                   1





CRYPT(3X)        MISCELLANEOUS LIBRARY FUNCTIONS        CRYPT(3X)


     in place to a similar array representing  the  bits  of  the
     argument  after  being  subjected  to  the hashing algorithm
     using the key set by des_setkey. If flag is zero, the  argu-
     ment is encrypted; if nonzero, 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.

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

     The  run_setkey  and  run_crypt  routines  are  designed for
     applications that need cryptographic capabilities,  such  as
     ed(l)  and  vi(l), that must be compatible with the crypt(l)
     user-level utility.  run_setkey establishes a  two-way  pipe
     connection with crypt(l) using key as the password argument.
     run_crypt takes a block of characters and transforms cleart-
     ext  or  ciphertext into their ciphertext or cleartext using
     crypt(l).

     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 con-
     nection  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
     crypt(l).

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


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


DIAGNOSTICS
     In the international version of crypt(3X), a  flag  argument
     of  1  to  des_encrypt  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.





SUPER-UX            Last change: Oct  3, 1997                   2