rc4加密的C源代码

rc4.h

#ifndef _RC4_H
#define _RC4_H

struct rc4_state
{
    int x, y, m[256];
};

void rc4_setup( struct rc4_state *s, unsigned char *key,  int length );
void rc4_crypt( struct rc4_state *s, unsigned char *data, int length );

#endif /* rc4.h */

rc4.c

/*
*  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"

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;
}

#ifdef TEST

#include <string.h>
#include <stdio.h>

/*
* ARC4 tests vectors from OpenSSL (crypto/rc4/rc4test.c)
*/

static unsigned char keys[7][30]={
        {8,0x01,0x23,0x45,0x67,0x89,0xab,0xcd,0xef},
        {8,0x01,0x23,0x45,0x67,0x89,0xab,0xcd,0xef},
        {8,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00},
        {4,0xef,0x01,0x23,0x45},
        {8,0x01,0x23,0x45,0x67,0x89,0xab,0xcd,0xef},
        {4,0xef,0x01,0x23,0x45},
        };

static unsigned char data_len[7]={8,8,8,20,28,10};
static unsigned char data[7][30]={
        {0x01,0x23,0x45,0x67,0x89,0xab,0xcd,0xef,0xff},
        {0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0xff},
        {0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0xff},
        {0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
           0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
           0x00,0x00,0x00,0x00,0xff},
        {0x12,0x34,0x56,0x78,0x9A,0xBC,0xDE,0xF0,
           0x12,0x34,0x56,0x78,0x9A,0xBC,0xDE,0xF0,
           0x12,0x34,0x56,0x78,0x9A,0xBC,0xDE,0xF0,
           0x12,0x34,0x56,0x78,0xff},
        {0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0xff},
        {0},
        };

static unsigned char output[7][30]={
        {0x75,0xb7,0x87,0x80,0x99,0xe0,0xc5,0x96,0x00},
        {0x74,0x94,0xc2,0xe7,0x10,0x4b,0x08,0x79,0x00},
        {0xde,0x18,0x89,0x41,0xa3,0x37,0x5d,0x3a,0x00},
        {0xd6,0xa1,0x41,0xa7,0xec,0x3c,0x38,0xdf,
         0xbd,0x61,0x5a,0x11,0x62,0xe1,0xc7,0xba,
         0x36,0xb6,0x78,0x58,0x00},
        {0x66,0xa0,0x94,0x9f,0x8a,0xf7,0xd6,0x89,
         0x1f,0x7f,0x83,0x2b,0xa8,0x33,0xc0,0x0c,
         0x89,0x2e,0xbe,0x30,0x14,0x3c,0xe2,0x87,
         0x40,0x01,0x1e,0xcf,0x00},
        {0xd6,0xa1,0x41,0xa7,0xec,0x3c,0x38,0xdf,0xbd,0x61,0x00},
        {0},
        };

int main( void )
{
    int i;
    struct rc4_state s;
    unsigned char buffer[30];

    printf( "\n RC4 Validation Tests:\n\n" );

    for( i = 0; i < 6; i++ )
    {
        printf( " Test %d ", i + 1 );

        memcpy( buffer, data[i], data_len[i] );

        rc4_setup( &s, &keys[i][1], keys[i][0] );
        rc4_crypt( &s, buffer, data_len[i] );

        if( memcmp( buffer, output[i], data_len[i] ) )
        {
            printf( "failed!\n" );
            return( 1 );
        }

        printf( "passed.\n" );
    }

    printf( "\n" );

    return( 0 );
}

#endif

===============================================================================

刚才浪费了好长的时间研究RC4加密算法。
关于RC4加密算法,可以参考百度百科:RC4算法

参考RC4经典加密算法代码(VB版)，写了个VBS版。
下面附有代码，我觉得应该没有错误。
但测试后却发现:
1, key不能使用中文
2, 不同编码的中文加密以后的值也是不同的
3, 加密以后太多的不可见字符，根本不适合web使用。
4, 也许变通一下会是一个不错的加密算法。比如我下面的直接输出asc码。

Function RC4(inp,key)
' //RC4加密算法的VBS版
' //by fisker

     Dim S(255), K(255), i
     Dim j, temp, Y, t, x
     Dim Outp

     For i = 0 To 255
     S(i) = i
     Next

     j = 1
     For i = 0 To 255
     If j > Len(key) Then j = 1
     K(i) = Asc(mid(key, j, 1))
     j = j + 1
     Next

     j = 0
     For i = 0 To 255
     j = (j + S(i) + K(i)) Mod 256
     temp = S(i)
     S(i) = S(j)
     S(j) = temp
     Next

     i = 0
     j = 0
     For x = 1 To Len(inp)
     i = (i + 1) Mod 256
     j = (j + S(i)) Mod 256
     temp = S(i)
     S(i) = S(j)
     S(j) = temp
     t = (S(i) + (S(j) Mod 256)) Mod 256
     Y = S(t)

     'Outp = Outp & (Asc(mid(inp, x, 1)) Xor Y)   
     Outp = Outp & Chr(Asc(mid(inp, x, 1)) Xor Y)   'RC4算法
     next

     RC4 = Outp

End Function