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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	   /* 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 follow-
       ing 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  restric-
	      tions.)

ATTRIBUTES
   Multithreading (see pthreads(7))
       The encrypt() and setkey() functions are not thread-safe.

       The encrypt_r() and setkey_r() functions are thread-safe.

CONFORMING TO
       The  functions encrypt() and setkey() conform to SVr4, SUSv2, and POSIX.1-2001.	The func-
       tions 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),

COLOPHON
       This  page  is  part of release 3.55 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/.

					    2013-07-22				       ENCRYPT(3)
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