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 exten-
       sions.

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 use-
       ful 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 3.27 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)