一个简单的解密程序

加密过程：

#include<iostream>

#include<fstream>

void main(void)

{

char strch,ch;

int i,x;

ifstream readfile;

ofstream writefile;

readfile.open("1.txt",ios::in | ios::nocreate);

if(!readfile)

{

cerr<<"cannot open thie file for input"<<endl;

exit(0); }

writefile.open("2.txt",ios::in | ios::nocreate);

if(!writefile)

{

cerr<<"cannot open the file for output"<<endl;

exit(0); }

while(!readfile.eof())

{

ch=readfile.get();

x=static_cast<int>(ch);

x=(x+3)%128;

strch=static_cast<char>(x);

writefile.put(strch);

}

}

相应的解密过程：

#include<iostream>

#include<string>

#include<fstream>

void main(void){

char strch,ch;

int i,x;

ifstream readfile;

ofstream writefile;

readfile.open("2.txt",ios::in | ios::nocreate);

if(!readfile)

{

cerr<<"cannot open thie file for input"<<endl;

exit(0);

}

writefile.open("3.txt",ios::in | ios::nocreate);

if(!writefile)

{

cerr<<"cannot open the file for output"<<endl;

exit(0);

}

while(!readfile.eof())

{

ch=readfile.get();

x=static_cast<int>(ch);

x=(x-3)%128;

strch=static_cast<char>(x);

writefile.put(strch);

}

}