.\" Portions Copyright © 2005-2006 Nokia. All rights reserved.

.\" FreeSec: libcrypt for NetBSD

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.\" Copyright (c) 1994 David Burren

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.\" $FreeBSD: src/lib/libcrypt/crypt.3,v 1.31 2005/02/09 18:03:14 ru Exp $

.\"

.Dd January 19, 1997

.Dt ENCRYPT 3

.Os

.Sh NAME

.Nm encrypt, setkey

.Nd encrypt 64-bit messages

.Sh LIBRARY

.Lb libcrypt

.Sh SYNOPSIS

.In unistd.h

.Ft void

.Fn encrypt "char block[64]" "int edflag"

.In stdlib.h

.Ft void

.Fn setkey "const char *key"

.Sh RETURN VALUES

The

.Fn encrypt 

and 

.Fn setkey

functions do not return any value.

.Sh DESCRIPTION

.Fn encrypt()

function encrypts and decrypts 64-bit messages. The algorithm used to perform 

encryption/decryption is Data Encryption Standard (DES).

.Pp

.Fn setkey()

is invoked to set the key for the DES machine.

.Fn setkey()'

s

.Fn key

parameter is an array of 64 bytes, and the numerical value of each byte in this

array is either 0 or 1. The 56-bit key for the DES algorithm is computed from the

.Fn key

parameter.

.Pp

.Fn encrypt

function either encrypts or decrypts the data block. The exact operation depends 

on the value of 

.Fn edflag

parameter. 

.Fn block

is encrypted if 

.Fn edflag

parameter is 0, and decrypted if 1 is being passed as the value of 

.Fn edflag 

parameter. 

.Fn block

is an array of 64 bytes, wherein the numerical value of each byte is either 0 or 1.

Like the 

.Fn setkey'

s

.Fn key 

parameter, 

.Fn block 

is a bit vector representation of the actual value that is encoded. It is modified in place

to return the result.

.Pp

.Fn encrypt

and

.Fn setkey

are not reentrant as the key is stored statically.

.Sh ERRORS

.Fn errno

should be set to zero prior to calling any of the above functions. The behavior of

.Fn encrypt

will be undefined if size of

.Fn block

argument is not 64.

.Sh EXAMPLE

.Bd -literal -offset indent

#include <stdlib.h>

#include <unistd.h>

void encrypt_user()

{

	/* bit vector containing the key */

	char key[64] = 

	{

			0, 0, 0, 0, 0, 0, 0, 1,

			0, 0, 1, 1, 0, 0, 0, 1,

			1, 1, 0, 1, 1, 0, 0, 1,

			0, 1, 1, 0, 0, 0, 0, 1,

			1, 0, 0, 1, 1, 1, 0, 1,

			1, 1, 0, 0, 0, 0, 0, 1,

			0, 0, 1, 1, 0, 1, 1, 1,

			0, 1, 1, 0, 1, 1, 1, 0

	};

	/* bit vector containing the data block to be encrypted */

	char block[64] = 

	{

		0, 1, 0, 1, 1, 1, 0, 0,

		1, 1, 0, 1, 0, 1, 0, 1,

		0, 1, 0, 0, 1, 1, 0, 0,

		1, 0, 1, 0, 1, 0, 0, 0,

		0, 0, 1, 1, 1, 1, 0, 1,

		1, 1, 1, 0, 1, 1, 1, 1,

		0, 1, 0, 1, 0, 1, 1, 1,

		1, 1, 0, 1, 1, 0, 1, 0

	};

	setkey(key);		/* Set the key for DES encryption */

	/* Perform encryption/decryption of the message block */

	encrypt(block, 0);	/* Encryption. The input block is modified in place

					 * to return the output to the user

					 */

	encrypt(block, 1);	/* Decryption. The input block is modified in place

					 * to return the result of the decryption operation

					 */

}

.Ed

.Sh SEE ALSO

.Sh HISTORY

.Sh BUGS

If 

.Fn encrypt

is called without priorly invoking 

.Fn setkey

the implementation assumes a bit vector consisting of all zeroes as the key

for the DES algorithm. In this scenaro the outcome of 

.Fn encrypt

function is different from that of Linux's.