encrypt(3) — Linux manual pages

Linux manual pages	Section 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 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 */
}

COLOPHON

This page is part of release 3.24 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/.

Copyright 2000 Nicolás Lichtmaier <nickdebian.org>
Created 2000-07-22 00:52-0300

This is free documentation; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of
the License, or (at your option) any later version.

The GNU General Public License's references to "object code"
and "executables" are to be interpreted as the output of any
document formatting or typesetting system, including
intermediate and printed output.

This manual is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

Modified 2002-07-23 19:21:35 CEST 2002 Walter Harms
<walter.harmsinformatik.uni-oldenburg.de>

Modified 2003-04-04, aeb

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`;
};