AES Decrypt a file in NodeJs

I've created some examples in both Java and Node.js that will encrypt and decrypt files. The code will be compatible as long as the same key and IV values are used, that is to say the Node code will decrypt the output from the Java and vice-versa.

Now I'm using text files as input here, but you can use any file type as input.

I've updated to use 128-bit AES in ECB mode.

The Key cannot be "1234" since it must be 128-bits long, so I've used the key given below (16 bytes / 128 bits).

Java

import java.io.*;
import javax.crypto.*;
import java.security.*;
import javax.crypto.spec.*;

public class fileEncrypter {

  private static final String key = "0123456789ABDCEF";

  public static void main(String[] args)
  {
      encryptFile(key, "java-input.txt", "java-output.txt");
      decryptFile(key, "java-output.txt", "java-decrypted.txt");
  }

  public static void encryptFile(String secret, String inputFile, String outputFile) 
  {
      try 
      {
          Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5PADDING");
          cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(secret.getBytes(), "AES"));

          byte[] inputData = readFile(inputFile);
          byte[] outputData = cipher.doFinal(inputData);
          writeToFile(outputFile, outputData);  
      } 
      catch (Exception e) 
      {
          System.out.println("Error while encrypting: " + e.toString());
      }
  }

  public static void decryptFile(String secret, String inputFile, String outputFile) 
    {
        try 
        {
            Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5PADDING");
            cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(secret.getBytes(), "AES"));

            byte[] inputData = readFile(inputFile);
            byte[] outputData = cipher.doFinal(inputData);
            writeToFile(outputFile, outputData);  
        } 
        catch (Exception e) 
        {
            System.out.println("Error while decrypting: " + e.toString());
        }
    }

    private static byte[] readFile(String fileName) throws IOException {
        byte[] data = new byte[(int) new File(fileName).length()];
        DataInputStream dis = new DataInputStream(new FileInputStream(fileName));
        dis.readFully(data);
        dis.close();
        return data;
    }

    private static void writeToFile(String fileName, byte[] data) throws IOException {
        final BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(new FileOutputStream(fileName));
        bufferedOutputStream.write(data, 0, data.length);
        bufferedOutputStream.close();
    }
}

Node.js

const crypto = require("crypto");
const Algorithm = "aes-128-ecb";
const fs = require("fs");

function encryptFile(key, inputFile, outputFile) {
    const inputData = fs.readFileSync(inputFile);
    const cipher = crypto.createCipheriv(Algorithm, key, Buffer.alloc(0));
    const output = Buffer.concat([cipher.update(inputData) , cipher.final()]);
    fs.writeFileSync(outputFile, output);
}

function decryptFile(key, inputFile, outputFile) {
    const inputData = fs.readFileSync(inputFile);
    const cipher = crypto.createDecipheriv(Algorithm, key, Buffer.alloc(0));
    const output = Buffer.concat([cipher.update(inputData) , cipher.final()]);
    fs.writeFileSync(outputFile, output);
}

const KEY = Buffer.from("0123456789ABDCEF", "utf8");

encryptFile(KEY, "node-input.txt", "node-output.txt");
decryptFile(KEY, "node-output.txt", "node-decrypted.txt");

I have solved this problem with the help of Terry Lennox. A big thanks to him first.

First Error:

error:06065064:digital envelope routines:EVP_DecryptFinal_ex:bad decrypt

This was a padding issue, By default, nodeJs uses PKCS padding so I had to set auto padding to false by using decipher.setAutoPadding(false);

This solved the first error

Secondly, I was using crypto.createDecipher(ALGORITHM, ENCRYPTION_KEY) which processes the key before using it. To solve this I changed the function to crypto.createDecipheriv(ALGORITHM, ENCRYPTION_KEY, null)

This was giving me error as we cannot pass null in place of IV value.

Since ECB does not require any IV, and we cannot pass null in place of IV I had to set my IV value to this Buffer.alloc(0)

This is the code that worked for me

function Decrypt_AES() {

    const ALGORITHM = 'aes-128-ecb';
    const key = "1234";
    const ENCRYPTION_KEY = key;

    var IV = Buffer.alloc(0);
    var decipher = crypto.createDecipheriv(ALGORITHM, ENCRYPTION_KEY, IV);
    decipher.setAutoPadding(false);
    var input = fs.createReadStream('test.enc');
    var output = fs.createWriteStream('test_copy.xls');

    input.pipe(decipher).pipe(output);

    output.on('finish', function () {
        console.log('Decrypted file written to disk!');
    });
    output.on('error', function (e) {
        console.log(e);
     });

}