I have big problem with encryption by ASCII

hello every body here

just today I knew I am stupid in C++ because I taken 2 hours thinking about this program

I have to write two programs

first program encrypt file from hard drive (.txt) and ask the user to enter the key to encrypt the file for example:

A=65 if we ask the user enter key and he enter 3

3+65 = 68 the letter after encrypt will be D because D=68

the kind of encryption is ASCII

second program same thing but decryption the file.

this my tried for quiestion 1

Code:

---

#include <iostream>
#include <fstream>
using namespace std;
void main()
{
        int key;
        char x;

        ifstream in_stream;
        ofstream out_stream;

        in_stream.open("encrypt.txt"); //it's already in the hard drive and contain some words or digits.
    out_stream.open("decrypt.txt");//the program it will be create this file.
        in_stream >> x;

       

        while(!in_stream.eof())
        {
                if(x>='a' && x<='z' || x=='A' && x=='Z' ||  x>=0 && x<9)
                {
                        cout <<"Enter the key to encrypt your file\n";
                        cin>>key;
                        in_stream.get(x);
                        x=key+x;
                        cout<<x<<endl;
                }
        }
        in_stream.close();
        out_stream.close();
}

---

So what's the problem?

the problem how can I encrypt the file.

the code doesn't work.

Here's some code for cin that encrypts with 3. You probably want the key to be set once and used for every character instead of a different key for each character. That way you don't have to keep save all the keys for decryption.

Code:

---

#include <iostream>
#include <cctype>


using namespace std;


int main() {
  int key = 3;
  char x;

  while ( cin.get( x ) ) {
    if ( isalnum( x ) ) {
      x += key;
    }

    cout << x;
  }
}

---

To decrypt you need the same key and just do -= instead of +=.

thank you very much Noir.

This is a very simply encryption scheme however ;)

Simple shift, easily broken, if you want to busy yourself in the future you can look into some more advanced stuff ;)

have fun!

try to open the file via fstream

Quote:

---

Originally Posted by Junior89

This is a very simply encryption scheme however ;)

Simple shift, easily broken, if you want to busy yourself in the future you can look into some more advanced stuff ;)

have fun!

---

This is most likely a homework thing. It says questions 1 and 2. I did something like this in CS160 I believe. It's call the ceaser cipher, or the ceaser shift, and at any rate, it was created by ceaser as a means of "encrypting" his messages so if lost they couldn't be figured out. Being that old, its not that bad of an idea lol. At any rate, don't bash the encryption if it was assinged... theres no reason to do something more complicated and get a bad grade due to incompetence in following directions.