AES encryption in Node.js and decryption on Scala

Question

I'm trying to decrypt AES on Scala (using javax.crypto.Cipher), the ciphertext was encrypted in Node.js app (using aes-js). and getting an error

• I'm using Electronic Codebook

Node (encryption)

var aesjs = require("aes-js");

// An example 128-bit key
var key = [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 ];
var key_128_array = new Uint8Array(key);

var key_128_hex = aesjs.utils.hex.fromBytes(key_128_array);
console.log(key_128_hex);
// 0102030405060708090a0b0c0d0e0f10


// Convert text to bytes
var text = 'TextMustBe16Byte';
var textBytes = aesjs.utils.utf8.toBytes(text);

var aesEcb = new aesjs.ModeOfOperation.ecb(key_128_array);
var encryptedBytes = aesEcb.encrypt(textBytes);

// To print or store the binary data, you may convert it to hex
var encryptedHex = aesjs.utils.hex.fromBytes(encryptedBytes);
console.log(encryptedHex);
// "a7d93b35368519fac347498dec18b458"

Scala (decryption)

import org.bouncycastle.jce.provider.BouncyCastleProvider
import javax.crypto.Cipher

val cipher = Cipher.getInstance("AES", new BouncyCastleProvider())

val key = "0102030405060708090a0b0c0d0e0f10";
val aesKeySpec = new SecretKeySpec(key.getBytes("UTF-8"), "AES")
cipher.init(Cipher.DECRYPT_MODE, aesKeySpec)

val msg = "a7d93b35368519fac347498dec18b458"
val decrypted = cipher.doFinal(msg.getBytes())
log.debug(s"decrypted data ${decrypted}")

And I'm getting the following error:

javax.crypto.BadPaddingException: pad block corrupted
        at org.bouncycastle.jcajce.provider.symmetric.util.BaseBlockCipher$BufferedGenericBlockCipher.doFinal(Unknown Source)
        at org.bouncycastle.jcajce.provider.symmetric.util.BaseBlockCipher.engineDoFinal(Unknown Source)
        at javax.crypto.Cipher.doFinal(Cipher.java:2164)
...

Any idea what I'm doing wrong? Any help would be greatly appreciated.

Answer 1

The problem is with the key and message formats. Key is represented as hex sting and calling .getBytes will return bytes of chars in UTF-8 and not actual key bytes. Java 8 has javax.xml.bind.DatatypeConverter that can convert a hex string into correct Array[Byte]. Same with msg, it has to be converted correctly into Array[Byte]

You have to specify cipher AES/ECB/NoPadding as you do use ecb in node-js.

import javax.crypto.spec.SecretKeySpec
import javax.xml.bind.DatatypeConverter

object DecryptApp extends App {

  import org.bouncycastle.jce.provider.BouncyCastleProvider
  import javax.crypto.Cipher

  val cipher = Cipher.getInstance("AES/ECB/NoPadding", new BouncyCastleProvider())

  val key = "0102030405060708090a0b0c0d0e0f10"
  val keyBytes = DatatypeConverter.parseHexBinary(key)
  val aesKeySpec = new SecretKeySpec(keyBytes, "AES")
  cipher.init(Cipher.DECRYPT_MODE, aesKeySpec)

  val msg = "a7d93b35368519fac347498dec18b458"
  val decrypted = cipher.doFinal(DatatypeConverter.parseHexBinary(msg))
  println(s"decrypted data ${decrypted.map(_.toChar).mkString}")

}