Question

Using java: Store the files in .txt format and use the readByte() and writeByte() methods.

File encryption is the science of writing the contents of a file in a secret code. Write an encryption program that works like a filter, reading the contents of one file, modifying the data into a code, and then writing the coded contents out to a second file. The second file will be a version of the first file, but written in a secret code. Although there are complex encryption techniques, you should come up with a simple one of your own. For example, you could read the first file one character at a time, and add 10 to the character code of each character before it is written to the second file.

Write a second program that decrypts the file produced by the program. The decryption program should read the contents of the coded file, restore the data to its original state, and write it to another file.

Please have readByte() and writeByte() in the answer. Every answer I've looked at on this site including one that I've received for the same question has chosen to ignore this.

Answer 1

If you have any problem with the code feel free to comment.

Encryption.java

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;

public class Encyption {

   public static void main(String[] args) {
       ArrayList<Character> encrypts = new ArrayList<>();// for holding encrypted characters

       // reading from the file
       try {
           // change the name and path of file accordingly
           DataInputStream dis = new DataInputStream(new FileInputStream("data.txt"));
           while (true) {
               try {
                   // reading using readByte
                   int encrypted = (int) dis.readByte() + 10;// adding 10 to char
                   encrypts.add((char) encrypted);// adding to the arraylist
               } catch (EOFException e) {
                   break;
               }
           }
           dis.close();
       } catch (IOException e) {
           System.out.println(e);
       }

       // writing to the file
       try {
           DataOutputStream dos = new DataOutputStream(new FileOutputStream("encrypt.txt"));

           for (Character ch : encrypts) {
               dos.writeByte(ch);// writing using write byte
           }

           dos.close();
       } catch (FileNotFoundException e) {
           e.printStackTrace();
       } catch (IOException e) {
           e.printStackTrace();
       }

   }

}

Decryption.java

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;

public class Decrption {

   public static void main(String[] args) {
       ArrayList<Character> decrypts = new ArrayList<>();//for holding decrpted characters

       try {
           //change the name and path of the file accordingly
           DataInputStream dis = new DataInputStream(new FileInputStream("encrypt.txt"));
           while (true) {
               try {
                   //reading using readByte
                   int encrypted = (int) dis.readByte() - 10;//decrypting
                   decrypts.add((char) encrypted);
                   System.out.println(decrypts);
               } catch (EOFException e) {
                   break;
               }
           }
           dis.close();
       } catch (IOException e) {
           System.out.println(e);
       }

       try {
           //change the name and path of the file accordingly
           DataOutputStream dos = new DataOutputStream(new FileOutputStream("decrypt.txt"));

           //writing to the file
           for (Character ch : decrypts) {
               dos.writeByte(ch);//wrting using writeByte
           }

           dos.close();
       } catch (FileNotFoundException e) {
           e.printStackTrace();
       } catch (IOException e) {
           e.printStackTrace();
       }

   }

}

Input

data.txt - Notepad File Edit Format View Help Something's not right

Output

encrypt.txt - Notepad File Edit Format View Help ||ywoºrsxq1}*xy^* | sqrx

decrypt.txt - Notepad File Edit Format View Help Something's not right