C++ Secure Chat System

A secure chat system in C++ consists of two programs that work together: one for encrypting and sending messages and the other for decrypting and displaying them.

Main Features

The system includes:

Program A (Sender)

• Encrypts messages using an algorithm like AES or XOR.
• Saves encrypted messages to a file.

Program B (Receiver)

• Reads encrypted messages from the file.
• Decrypts them using the same encryption method.

---

Program A: Sender

This program encrypts a message and saves it to a file.

Code:

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

// Simple XOR encryption
string encryptMessage(const string& message, char key) {
    string encrypted = message;
    for (char& c : encrypted) {
        c ^= key;
    }
    return encrypted;
}

int main() {
    string message;
    char key = 'X'; // Secret key

    cout << "Enter message to encrypt: ";
    getline(cin, message);

    string encryptedMessage = encryptMessage(message, key);

    // Save to file
    ofstream outFile("secure_message.txt");
    if (outFile) {
        outFile << encryptedMessage;
        outFile.close();
        cout << "Message encrypted and saved.\n";
    } else {
        cout << "Error saving message!\n";
    }

    return 0;
}

---

Program B: Receiver

This program reads an encrypted message from the file and decrypts it.

Code:

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

// Simple XOR decryption (same as encryption)
string decryptMessage(const string& encryptedMessage, char key) {
    string decrypted = encryptedMessage;
    for (char& c : decrypted) {
        c ^= key;
    }
    return decrypted;
}

int main() {
    string encryptedMessage;
    char key = 'X'; // Same secret key

    // Read from file
    ifstream inFile("secure_message.txt");
    if (inFile) {
        getline(inFile, encryptedMessage);
        inFile.close();

        string decryptedMessage = decryptMessage(encryptedMessage, key);
        cout << "Decrypted message: " << decryptedMessage << endl;
    } else {
        cout << "Error reading message!\n";
    }

    return 0;
}

---

How It Works Together

1. Run Program A (Sender):

   • Enter a message.
   • The message is encrypted and saved to a file.

2. Run Program B (Receiver):

   • Reads the encrypted message from the file.
   • Decrypts it using the same key.
   • Displays the original message.

This simple C++ secure chat system demonstrates basic encryption and decryption using XOR. For stronger security, AES or other cryptographic algorithms should be considered.