ENCRYPT(3)		   Linux Programmers Manual		   ENCRYPT(3)



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

SYNOPSIS
       #define _XOPEN_SOURCE
       #include 

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

       #define _XOPEN_SOURCE
       #include 

       void setkey(const char *key);

       #define _GNU_SOURCE
       #include 

       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 reen
       trant 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 2.2.
       To do useful work the key[] and txt[] arrays must be filled with a use
       ful bit pattern.

       #define _XOPEN_SOURCE
       #include 
       #include 

       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 3.05 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)