encrypt

ENCRYPT(3)		   Cryptographic Functions		   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 parameter 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  parameter	 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, 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.)

EXAMPLE
       You  need to link with libcrypt to compile this example with glibc2.2.
       To do useful work the key[] and txt[] array  must  be  filled  with  a
       useful  bit  pattern.  Note  that the <crypt.h> header unconditionally
       gives the prototypes for setkey() and encrypt().

       #include <crypt.h>

       main() {
	 char key[64];	    /* bit pattern for key */
	 char txt[64];	    /* bit pattern for messages */
	 setkey(key);
	 encrypt(txt, 0);   /* encode */
	 encrypt(txt, 1);   /* decode */
       }

NOTE
       In glibc2.2 these functions use the DES algorithm.

CONFORMING TO
       The functions encrypt() and setkey() conform to SVID, SUSv2, and POSIX
       1003.1-2001.   The functions encrypt_r() and setkey_r() are GNU exten-
       sions.

SEE ALSO
       cbc_crypt(3), crypt(3), ecb_crypt(3), fcrypt(3)



glibc2				  2003-04-04			   ENCRYPT(3)