ncbc_enc.c

这是一个DES加解密的C程序。其中实现了一重DES、三重DES、DES的两种工作模式：ECB和CBC。

/* crypto/des/ncbc_enc.c */
/*
 * #included by:
 *    cbc_enc.c  (DES_cbc_encrypt)
 *    des_enc.c  (DES_ncbc_encrypt)
 */
/* Copyright (C) 1995-1998 Eric Young ([e-mail])
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young ([e-mail]).
 * The implementation was written so as to conform with Netscapes SSL.
 * 
 * This library is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.  The following conditions
 * apply to all code found in this distribution, be it the RC4, RSA,
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
 * included with this distribution is covered by the same copyright terms
 * except that the holder is Tim Hudson ([e-mail]).
 * 
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.
 * If this package is used in a product, Eric Young should be given attribution
 * as the author of the parts of the library used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young ([e-mail])"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
 * 4. If you include any Windows specific code (or a derivative thereof) from 
 *    the apps directory (application code) you must include an acknowledgement:
 *    "This product includes software written by Tim Hudson ([e-mail])"
 * 
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * 
 * The licence and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution licence
 * [including the GNU Public Licence.]
 */

#include "des_locl.h"

#ifdef CBC_ENC_C__DONT_UPDATE_IV
void DES_cbc_encrypt(const unsigned char *in, unsigned char *out, long length,
		     DES_key_schedule *_schedule, DES_cblock *ivec, int enc)
#else
void DES_ncbc_encrypt(const unsigned char *in, unsigned char *out, long length,
		     DES_key_schedule *_schedule, DES_cblock *ivec, int enc)
#endif
	{
	register DES_LONG tin0,tin1;
	register DES_LONG tout0,tout1,xor0,xor1;
	register long l=length;
	DES_LONG tin[2];
	unsigned char *iv;

	iv = &(*ivec)[0];

	if (enc)
		{
		c2l(iv,tout0);
		c2l(iv,tout1);
		for (l-=8; l>=0; l-=8)
			{
			c2l(in,tin0);
			c2l(in,tin1);
			tin0^=tout0; tin[0]=tin0;
			tin1^=tout1; tin[1]=tin1;
			DES_encrypt1((DES_LONG *)tin,_schedule,DES_ENCRYPT);
			tout0=tin[0]; l2c(tout0,out);
			tout1=tin[1]; l2c(tout1,out);
			}
		if (l != -8)
			{
			c2ln(in,tin0,tin1,l+8);
			tin0^=tout0; tin[0]=tin0;
			tin1^=tout1; tin[1]=tin1;
			DES_encrypt1((DES_LONG *)tin,_schedule,DES_ENCRYPT);
			tout0=tin[0]; l2c(tout0,out);
			tout1=tin[1]; l2c(tout1,out);
			}
#ifndef CBC_ENC_C__DONT_UPDATE_IV
		iv = &(*ivec)[0];
		l2c(tout0,iv);
		l2c(tout1,iv);
#endif
		}
	else
		{
		c2l(iv,xor0);
		c2l(iv,xor1);
		for (l-=8; l>=0; l-=8)
			{
			c2l(in,tin0); tin[0]=tin0;
			c2l(in,tin1); tin[1]=tin1;
			DES_encrypt1((DES_LONG *)tin,_schedule,DES_DECRYPT);
			tout0=tin[0]^xor0;
			tout1=tin[1]^xor1;
			l2c(tout0,out);
			l2c(tout1,out);
			xor0=tin0;
			xor1=tin1;
			}
		if (l != -8)
			{
			c2l(in,tin0); tin[0]=tin0;
			c2l(in,tin1); tin[1]=tin1;
			DES_encrypt1((DES_LONG *)tin,_schedule,DES_DECRYPT);
			tout0=tin[0]^xor0;
			tout1=tin[1]^xor1;
			l2cn(tout0,tout1,out,l+8);
#ifndef CBC_ENC_C__DONT_UPDATE_IV
			xor0=tin0;
			xor1=tin1;
#endif
			}
#ifndef CBC_ENC_C__DONT_UPDATE_IV 
		iv = &(*ivec)[0];
		l2c(xor0,iv);
		l2c(xor1,iv);
#endif
		}
	tin0=tin1=tout0=tout1=xor0=xor1=0;
	tin[0]=tin[1]=0;
	}