利用异或的性质来对文件进行加密：

复制代码 代码如下:

c=a^b

c^b=a

#include "stdio.h"

#include "stdlib.h"

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

{

FILE *fp1,*fp2;

char c,ch;

long j;

if(3!=argc)

{

printf("Command error/n");

exit(1);

}

if((fp1=fopen(argv[1],"rb"))==NULL)

{

printf("Can not open the source file/n");

exit(1);

}

if(NULL==(fp2=fopen(argv[2],"wb")))

{

printf("Can not open the aim file/n");

exit(1);

}

printf("Please input the password:/n");

scanf("%i",&j);

srand(j);

ch=fgetc(fp1);

while(!feof(fp1))

{

c=rand();

ch=ch^c;

fputc(ch,fp2);

ch=fgetc(fp1);

}

fclose(fp1);

fclose(fp2);

}