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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 3.23 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

                                  2003-04-04                        ENCRYPT(3)