Java Encryption With AES and MAC

Question

I am trying to figure out a way to complete my Java coursework. I am expected to encrypt a file but honestly I didn't really understand the instructions. I achieved file encryption and decryption however I have doubts that it does the thing instructions says. The instruction is as following:

The encryption has three stages:
Generate 16-byte random data as the Initial Vector (IV) that is needed for the CBC mode
Apply the AES cipher to encrypt the content of the file in the CBC mode using the PKCS5 padding scheme.
Apply a MAC cipher (e.g., “HmacSHA1”) to compute a MAC that encapsulates IV and ciphertext
The encrypted file will be the concatenation of the following data: 16-byte IV || ciphertext || 20-byte HMAC

The code I have written is like this, it successfully encrypts a text file. This is the whole code for my application.

import java.io.FileNotFoundException;
import java.io.*;
import java.util.Scanner;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.security.AlgorithmParameters;
import java.security.SecureRandom;
import java.security.spec.KeySpec;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;

public class AESFileEncryption {

/*public AESFileEncryption(String nameoffile){

}
public String FileReturn(String filename){
    String fl = filename;       
    return fl;      
}*/

public static void main(String[] args) throws Exception {

    File f = new File("plainfile.txt");
    File g = new File("plainfile.txt.8102");
    File fl = new File("plainfile.txt.8102");

    if(g.exists() && !g.isDirectory()){
        System.out.println("The file is already encrypted...");
        String fname = fl.getAbsolutePath();
        System.out.print("Absolute Encrypted File Pathname => "+ fname);
        System.exit(0);
    }       
    else if(f.exists() && !f.isDirectory()) { 
         System.out.println(" The file is found.The encryption process is going to begin...");

    }       
    else{
         System.out.println(" The file is missing!!!!");
         System.exit(0);
    }

    // file to be encrypted
    FileInputStream inFile = new FileInputStream("plainfile.txt");       

    // encrypted file
    FileOutputStream outFile = new FileOutputStream("plainfile.txt.8102");


    // password to encrypt the file
    Scanner scan= new Scanner(System.in);
    System.out.println("Enter the password : => ");
    String password= scan.nextLine();

    //String password = "javapapers";

    // password, iv and salt should be transferred to the other end
    // in a secure manner

    // salt is used for encoding
    // writing it to a file
    // salt should be transferred to the recipient securely
    // for decryption
    byte[] salt = new byte[8];
    SecureRandom secureRandom = new SecureRandom();
    secureRandom.nextBytes(salt);
    FileOutputStream saltOutFile = new FileOutputStream("salt.enc");
    saltOutFile.write(salt);
    saltOutFile.close();

    SecretKeyFactory factory = SecretKeyFactory
            .getInstance("PBKDF2WithHmacSHA1");
    KeySpec keySpec = new PBEKeySpec(password.toCharArray(), salt, 65536,
            256);
    SecretKey secretKey = factory.generateSecret(keySpec);
    SecretKey secret = new SecretKeySpec(secretKey.getEncoded(), "AES");

    //
    Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
    cipher.init(Cipher.ENCRYPT_MODE, secret);
    AlgorithmParameters params = cipher.getParameters();

    // iv adds randomness to the text and just makes the mechanism more
    // secure
    // used while initializing the cipher
    // file to store the iv
    FileOutputStream ivOutFile = new FileOutputStream("iv.enc");
    byte[] iv = params.getParameterSpec(IvParameterSpec.class).getIV();
    ivOutFile.write(iv);
    ivOutFile.close();

    //file encryption
    byte[] input = new byte[64];
    int bytesRead;

    while ((bytesRead = inFile.read(input)) != -1) {
        byte[] output = cipher.update(input, 0, bytesRead);
        if (output != null)
            outFile.write(output);
    }

    byte[] output = cipher.doFinal();
    if (output != null)
        outFile.write(output);

    inFile.close();
    outFile.flush();
    outFile.close();

    System.out.println("File Encrypted.");

    }

}

Java Encryption With AES and MAC

Answers (1)

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