// File Name: FileEncryptor.java

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;

public class FileEncryptor {

public static void main(String[] args) {

// A simple secret key. You can change this to any character.

char secretKey = 'K';

// The name of the file you want to encrypt.

// It must be in the same folder as your project.

String originalFilePath = "my_secret_message.txt";

// Names for the output files.

String encryptedFilePath = "encrypted_file.dat";

String decryptedFilePath = "decrypted_message.txt";

try {

System.out.println("Starting encryption...");

encryptFile(originalFilePath, encryptedFilePath, secretKey);

System.out.println("File encrypted successfully! Output: " + encryptedFilePath);

System.out.println("\nStarting decryption...");

// We use the SAME function to decrypt! That's the magic of XOR.

encryptFile(encryptedFilePath, decryptedFilePath, secretKey);

System.out.println("File decrypted successfully! Output: " + decryptedFilePath);

} catch (IOException e) {

System.out.println("An error occurred. Make sure '" + originalFilePath + "' exists in your project folder.");

e.printStackTrace();

}

}

/**

* Reads a file, encrypts/decrypts its content using a key, and writes to a new file.

* @param sourcePath Path of the input file.

* @param destinationPath Path for the output file.

* @param key The secret key for XOR operation.

* @throws IOException If there's an error reading or writing files.

*/

public static void encryptFile(String sourcePath, String destinationPath, char key) throws IOException {

try (FileInputStream inputStream = new FileInputStream(sourcePath);

FileOutputStream outputStream = new FileOutputStream(destinationPath)) {

int byteRead;

while ((byteRead = inputStream.read()) != -1) {

// This is the core encryption/decryption logic!

// The ^ symbol is the bitwise XOR operator.

int encryptedByte = byteRead ^ key;

outputStream.write(encryptedByte);

}

}

}

}