encrypt man page on ElementaryOS

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ENCRYPT(3)		   Linux Programmer's Manual		    ENCRYPT(3)

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

       #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.

       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.

       These functions do not return any value.

       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.)

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

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

       The functions encrypt()	and  setkey()  conform	to  SVr4,  SUSv2,  and
       POSIX.1-2001.   The functions encrypt_r() and setkey_r() are GNU exten‐

       In glibc 2.2 these functions use the DES algorithm.

       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>

	   char key[64];      /* bit pattern for key */
	   char txt[64];      /* bit pattern for messages */

	   encrypt(txt, 0);   /* encode */
	   encrypt(txt, 1);   /* decode */

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

       This page is part of release 3.54 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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