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ENCRYPT(3)                 Linux Programmer's Manual                ENCRYPT(3)



NAME
       encrypt, setkey, encrypt_r, setkey_r - encrypt 64-bit messages

SYNOPSIS
       #define _XOPEN_SOURCE
       #include <unistd.h>

       void encrypt(char block[64], int edflag);

       #define _XOPEN_SOURCE
       #include <stdlib.h>

       void setkey(const char *key);

       #define _GNU_SOURCE
       #include <crypt.h>

       void setkey_r(const char *key, struct crypt_data *data);
       void encrypt_r(char *block, int edflag, struct crypt_data *data);

       Each of these requires linking with -lcrypt.

DESCRIPTION
       These  functions  encrypt  and decrypt 64-bit messages.  The setkey() function sets
       the key used by encrypt().  The key argument used here is an  array  of  64  bytes,
       each  of  which  has  numerical  value  1 or 0.  The bytes key[n] where n=8*i-1 are
       ignored, so that the effective key length is 56 bits.

       The encrypt() function modifies the passed buffer, encoding if  edflag  is  0,  and
       decoding  if  1 is being passed.  Like the key argument, also block is a bit vector
       representation of the actual value that is encoded.  The result is returned in that
       same vector.

       These  two  functions  are  not  reentrant, that is, the key data is kept in static
       storage.  The functions setkey_r() and  encrypt_r()  are  the  reentrant  versions.
       They use the following structure to hold the key data:

           struct crypt_data {
               char     keysched[16 * 8];
               char     sb0[32768];
               char     sb1[32768];
               char     sb2[32768];
               char     sb3[32768];
               char     crypt_3_buf[14];
               char     current_salt[2];
               long int current_saltbits;
               int      direction;
               int      initialized;
           };

       Before calling setkey_r() set data->initialized to zero.

RETURN VALUE
       These functions do not return any value.

ERRORS
       Set errno to zero before calling the above functions.  On success, it is unchanged.

       ENOSYS The function is not provided.  (For example because  of  former  USA  export
              restrictions.)

CONFORMING TO
       The functions encrypt() and setkey() conform to SVr4, SUSv2, and POSIX.1-2001.  The
       functions encrypt_r() and setkey_r() are GNU extensions.

NOTES
       In glibc 2.2 these functions use the DES algorithm.

EXAMPLE
       You need to link with libcrypt to compile this example with glibc.   To  do  useful
       work the key[] and txt[] arrays must be filled with a useful bit pattern.

       #define _XOPEN_SOURCE
       #include <unistd.h>
       #include <stdlib.h>

       int
       main(void)
       {
           char key[64];      /* bit pattern for key */
           char txt[64];      /* bit pattern for messages */

           setkey(key);
           encrypt(txt, 0);   /* encode */
           encrypt(txt, 1);   /* decode */
       }

SEE ALSO
       cbc_crypt(3), crypt(3), ecb_crypt(3), feature_test_macros(7)

COLOPHON
       This page is part of release 3.22 of the Linux man-pages project.  A description of
       the project, and information about reporting bugs, can be found at  http://www.ker-
       nel.org/doc/man-pages/.



                                  2003-04-04                        ENCRYPT(3)

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