arcfour.cpp

KeePassX用于保护密码的安全

/***************************************************************************
 *   Copyright (C) 2005-2006 by Tarek Saidi                                *
 *   [e-mail]                                                  *
 *                                                                         *
 *   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 <QByteArray>
#include "arcfour.h"


static inline void swap_byte(unsigned char *a, unsigned char *b)
    {
        unsigned char swapByte;

        swapByte = *a;
        *a = *b;      
        *b = swapByte;
    } 

void CArcFour::setKey(byte* key_data_ptr, int key_data_len){
RawKey=QByteArray((const char*)key_data_ptr,key_data_len);
}

void CArcFour::prepareKey(){
 unsigned char swapByte;
 unsigned char index1;
 unsigned char index2;
 unsigned char* state;
 short counter;    

 state = &key.state[0];        
 for(counter = 0; counter < 256; counter++)              
 state[counter] = counter;              
 key.x = 0;    
 key.y = 0;    
 index1 = 0;    
 index2 = 0;            
 for(counter = 0; counter < 256; counter++)      
 {              
   index2 = (RawKey.at(index1) + state[counter] + index2) % 256;                
   swap_byte(&state[counter], &state[index2]);            
   index1 = (index1 + 1) % RawKey.size();  
  }      
}

void CArcFour::encrypt(const byte* src, byte* dst,int length){
//qDebug("Key:%s",RawKey.data());
		prepareKey();
        unsigned char x;
        unsigned char y;
        unsigned char* state;
        unsigned char xorIndex;
        short counter;              

        x = key.x;    
        y = key.y;    

        state = &key.state[0];        
        for(counter = 0; counter < length; counter ++)      
        {              
             x = (x + 1) % 256;                      
             y = (state[x] + y) % 256;              
             swap_byte(&state[x], &state[y]);                        

             xorIndex = (state[x] + state[y]) % 256;                

			 dst[counter]=src[counter]^state[xorIndex];        
         }              
         key.x = x;    
         key.y = y;
}