rc4.cpp

加密解密 用于数据的加密,解密 包括 RSA rc4 md5 等,多种加密方法

//rc4.cpp
/*
 *  An implementation of the ARC4 algorithm
 *
 *  Copyright (C) 2001-2003  Christophe Devine
 *
 *  This program is free software; 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.
 *
 *  This program 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.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include "rc4.h"
#include <stdlib.h>
#include <windows.h>
void rc4_makey(  unsigned char *key, int keylength  )
{
	//由于RC4算法加密是采用的xor，所以，一旦子密钥序列出现了重复，
	//密文就有可能被破解。RC4算法生成的子密钥序列是否会出现重复呢
	//经过我的测试，存在部分弱密钥，使得子密钥序列在不到100万字节
	//内就发生了完全的重复，如果是部分重复，则可能在不到10万字节
	//内就能发生重复，因此，推荐在使用RC4算法时，必须对加密密钥进
	//行测试，判断其是否为弱密钥。

	//有办法让他不重复。但是也觉得没有必要
    srand(GetTickCount());
	//生成密钥
	for (long i = 0 ;i<keylength;i++)
	{
		try		
		{
			key[i] =rand()%256;//怕数组越界
		}
		catch (...)
		{
            break;			
		}		
	}
}
void rc4_setup( struct rc4_state *s, unsigned char *key,  int length )
{
    int i, j, k, *m, a;

    s->x = 0;
    s->y = 0;
    m = s->m;

    for( i = 0; i < 256; i++ )
    {
        m[i] = i;
    }

    j = k = 0;

    for( i = 0; i < 256; i++ )
    {
        a = m[i];
        j = (unsigned char) ( j + a + key[k] );
        m[i] = m[j]; 
		m[j] = a;
        if( ++k >= length )
			k = 0;
    }
}

void rc4_crypt( struct rc4_state *s, unsigned char *data, int length )
{ 
    int i, x, y, *m, a, b;

    x = s->x;
    y = s->y;
    m = s->m;

    for( i = 0; i < length; i++ )
    {
        x = (unsigned char)( x + 1 ); 
		a = m[x];
        y = (unsigned char)( y + a );
        m[x] = b = m[y];
        m[y] = a;
        data[i] ^= m[(unsigned char) ( a + b )];
    }

    s->x = x;
    s->y = y;
}