NAME

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

SYNOPSIS

       #define _XOPEN_SOURCE       /* See feature_test_macros(7) */
       #include <unistd.h>

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

       #define _XOPEN_SOURCE       /* See feature_test_macros(7) */
       #include <stdlib.h>

       void setkey(const char *key);

       #define _GNU_SOURCE         /* See feature_test_macros(7) */
       #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.)

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌────────────────────────┬───────────────┬──────────────────────┐
       │Interface               │ Attribute     │ Value                │
       ├────────────────────────┼───────────────┼──────────────────────┤
       │encrypt(), setkey()     │ Thread safety │ MT-Unsafe race:crypt │
       ├────────────────────────┼───────────────┼──────────────────────┤
       │encrypt_r(), setkey_r() │ Thread safety │ MT-Safe              │
       └────────────────────────┴───────────────┴──────────────────────┘

CONFORMING TO

       encrypt(), setkey(): POSIX.1-2001, POSIX.1-2008, SUS, SVr4.

       The functions encrypt_r() and setkey_r() are GNU extensions.

NOTES

       In glibc 2.2, these functions use the DES algorithm.

EXAMPLE

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

       int
       main(void)
       {
           char key[64];
           char orig[9] = "eggplant";
           char buf[64];
           char txt[9];
           int i, j;

           for (i = 0; i < 64; i++) {
               key[i] = rand() & 1;
           }

           for (i = 0; i < 8; i++) {
               for (j = 0; j < 8; j++) {
                   buf[i * 8 + j] = orig[i] >> j & 1;
               }
               setkey(key);
           }
           printf("Before encrypting: %s\n", orig);

           encrypt(buf, 0);
           for (i = 0; i < 8; i++) {
               for (j = 0, txt[i] = '\0'; j < 8; j++) {
                   txt[i] |= buf[i * 8 + j] << j;
               }
               txt[8] = '\0';
           }
           printf("After encrypting:  %s\n", txt);

           encrypt(buf, 1);
           for (i = 0; i < 8; i++) {
               for (j = 0, txt[i] = '\0'; j < 8; j++) {
                   txt[i] |= buf[i * 8 + j] << j;
               }
               txt[8] = '\0';
           }
           printf("After decrypting:  %s\n", txt);
           exit(EXIT_SUCCESS);
       }

SEE ALSO

       cbc_crypt(3), crypt(3), ecb_crypt(3),

COLOPHON

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                                                   2015-08-08                                         ENCRYPT(3)