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

//exchange between two
void swap(unsigned char *s1,unsigned char *s2){
char temp;
temp=*s1;
*s1=*s2;
*s2=temp;
}
//create s_box
void re_S(unsigned char *S){
unsigned int i;
for(i=0;i<256;i++)
   S[i]=i;
}

void re_T(unsigned char *T,char *key){
int i;
int keylen;
keylen=strlen(key);
for(i=0;i<256;i++)
   T[i]=key[i%keylen];
//for(i=0;i<256;i++)
//   printf("%c",T[i]);
}
//chaos s_box
void re_Sbox(unsigned char *S,unsigned char *T){
int i;
int j=0;
for(i=0;i<256;i++){
   j=(j+S[i]+T[i])%256;
   swap(&S[i],&S[j]);
	}
}
//initial
void re_RC4(unsigned char *S,char *key){
char T[255]={0};
re_S(S);
re_T(T,key);
re_Sbox(S,T);
}
//encrypt or decrypt
void RC4(FILE *readfile,FILE *writefile,char *key){ 

unsigned char S[256]={0};
unsigned char readbuf[1];
int i,j,t; 
re_RC4(S,key);//To create 256 bit sub_key sequence
i=j=0;
while(fread(readbuf,1,1,readfile)){
   i = (i + 1) % 256;
   j = (j + S[i]) % 256;
   swap(&S[i],&S[j]);
   t = (S[i] + (S[j] % 256)) % 256;
   readbuf[0]=readbuf[0]^S[t];//從256bit子密鑰序列，隨機(jī)地選一bit來(lái)做異或運(yùn)算
   fwrite(readbuf,1,1,writefile);
   memset(readbuf,0,1);
	}
printf("加密|解密成功!!!\n");
}


int main(int argc,char *argv[]){

char *Filename1,*Filename2;
char *key;
FILE *file1,*file2;
Filename1 = argv[1];
Filename2 = argv[2];
key=argv[3];
if ( argc == 4){
   printf("**********************正在加密中*******************\n");
	}
else{ 
   printf("輸入格式： \n");
   printf("文件名|加密或解密文件名|存放文件名|密鑰 \n");
   return -1; 
	}
if ((file1= fopen(Filename1,"rb")) == NULL|| (file2 = fopen(Filename2,"wb"))==NULL){  
   printf("Can't open file\n");
   return -1;
	}
RC4(file1,file2,key);
fclose(file1);
fclose(file2);
return 0;
}
/************************************************
試驗(yàn)步驟：
1.編譯、調(diào)試源代碼，在Debug下生成labrc4.exe可執(zhí)行文件
2.打開(kāi)命令編輯窗口，>f://源代碼所在目錄
3.F：\cd exe
4:F:\exe\dir//列出該目錄下的所有文件及文件夾，進(jìn)入到rc4\Debug\下，可以看到labrc4.exe
5.labrc4 file1.txt file2.txt 0110010//其中file1.txt是明文所在的文件，
file2.txt是用來(lái)存放密文的文件，0110010為初始密鑰。
需要注意的是：labrc4.exe file1.txt file2.txt須在同一個(gè)文件夾下面。
***************************************************/