crypt(3X) — AMIX 1.1



crypt(3X)        MISCELLANEOUS LIBRARY FUNCTIONS        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 *p, const char *key);

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

     int crypt_close(int *p);

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.

     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, 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.





          Last change: C Programming Language Utilities         1



crypt(3X)        MISCELLANEOUS LIBRARY FUNCTIONS        crypt(3X)



     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  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
     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 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 block is coming from.
     count is the number of characters in block,  and  connection
     is  an array containing indices to a table of input and out-
     put file streams. When encryption is  finished,  crypt_close
     is used to terminate the connection with the crypt utility.

     run_setkey returns -1 if a connection with the crypt utility
     cannot  be  established.  This result will occur in interna-
     tional versions of the UNIX system in which the crypt  util-
     ity 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  rou-
     tine library libcrypt.a.

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

DIAGNOSTICS
     In the international version of crypt(3X), a  flag  argument
     of 1 to encrypt or des_encrypt is not accepted, and errno is



          Last change: C Programming Language Utilities         2



crypt(3X)        MISCELLANEOUS LIBRARY FUNCTIONS        crypt(3X)



     set to ENOSYS to indicate  that  the  functionality  is  not
     available.

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

















































          Last change: C Programming Language Utilities         3

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