Java Code House

package com.javaingrab.security.encrypt;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;


public class AESEncryptor {

 public void encrypt(String fname) throws Exception{
  KeyGenerator keyGen = KeyGenerator.getInstance("AES");
  keyGen.init(256);  //using AES-256
  SecretKey key = keyGen.generateKey();  //generating key
  Cipher aesCipher = Cipher.getInstance("AES");  //getting cipher for AES
  aesCipher.init(Cipher.ENCRYPT_MODE, key);  //initializing cipher for encryption with key
  
  //creating file output stream to write to file
  try(FileOutputStream fos = new FileOutputStream(fname+".aes")){
   //creating object output stream to write objects to file
   ObjectOutputStream oos = new ObjectOutputStream(fos);
   oos.writeObject(key);  //saving key to file for use during decryption

   //creating file input stream to read contents for encryption
   try(FileInputStream fis = new FileInputStream(fname)){
    //creating cipher output stream to write encrypted contents
    try(CipherOutputStream cos = new CipherOutputStream(fos, aesCipher)){
     int read;
     byte buf[] = new byte[4096];
     while((read = fis.read(buf)) != -1)  //reading from file
      cos.write(buf, 0, read);  //encrypting and writing to file
    }
   }
  }
  
 }
 
 public void decrypt(String fname)throws Exception{
  SecretKey key =null;
    
  //creating file input stream to read from file
  try(FileInputStream fis = new FileInputStream(fname)){
   //creating object input stream to read objects from file
   ObjectInputStream ois = new ObjectInputStream(fis);
   key = (SecretKey)ois.readObject();  //reading key used for encryption
   
   Cipher aesCipher = Cipher.getInstance("AES");  //getting cipher for AES
   aesCipher.init(Cipher.DECRYPT_MODE, key);  //initializing cipher for decryption with key
   //creating file output stream to write back original contents
   try(FileOutputStream fos = new FileOutputStream(fname+".dec")){
    //creating cipher input stream to read encrypted contents
    try(CipherInputStream cis = new CipherInputStream(fis, aesCipher)){
     int read;
     byte buf[] = new byte[4096];
     while((read = cis.read(buf)) != -1)  //reading from file
      fos.write(buf, 0, read);  //decrypting and writing to file
    }
   }
  }
 
 }
 
 public static void main(String[] args) throws Exception {
  AESEncryptor obj = new AESEncryptor();
  obj.encrypt("clear.txt");
  obj.decrypt("clear.txt.aes");
 }

}

NOTE : You will need the clear.txt file which is the file to be encrypted to execute the code. The encrypted file will be placed in the same directory with same name as original file but with an extension ".aes". The decrypted file will have the same name as the encrypted file but with extension ".dec", this is done deliverately for you people to check whether the original conetents are same as the decrypted one.
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