How to Decrypt AES-Encrypted Text in Java When Encrypted in Go?

AES Encryption in Go and Decryption in Java

Question:

I have successfully encrypted text using AES in Go. However, I face challenges decrypting the encrypted text in Java. Can you provide assistance in understanding the Java decryption flow and a working Java decoder?

Answer:

Java Decoder:

<code class="java">import java.nio.charset.StandardCharsets;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
import java.util.Base64;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.IvParameterSpec;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKeySpec;

public class AesDecrypter {

    public static String decode(String base64Text, byte[] key) throws NoSuchPaddingException, NoSuchAlgorithmException,
            InvalidAlgorithmParameterException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException {

        byte[] inputArr = Base64.getUrlDecoder().decode(base64Text);
        SecretKeySpec skSpec = new SecretKeySpec(key, "AES");
        Cipher cipher = Cipher.getInstance("AES/CFB/NoPadding");
        int blockSize = cipher.getBlockSize();
        IvParameterSpec iv = new IvParameterSpec(Arrays.copyOf(inputArr, blockSize));
        byte[] dataToDecrypt = Arrays.copyOfRange(inputArr, blockSize, inputArr.length);
        cipher.init(Cipher.DECRYPT_MODE, skSpec, iv);
        byte[] result = cipher.doFinal(dataToDecrypt);
        return new String(result, StandardCharsets.UTF_8);
    }

}</code>

Scala Decoder:

<code class="scala">import java.nio.charset.StandardCharsets
import javax.crypto._
import java.security.spec.IvParameterSpec
import java.security.spec.SecretKeySpec
import java.util.Base64

object AesDecrypter {
  def decode(input:String, key:String): String = {
    val cipher = Cipher.getInstance("AES/CFB/NoPadding")
    val blockSize = cipher.getBlockSize()
    val keyBytes = key.getBytes()
    val inputArr = Base64.getUrlDecoder().decode(input)
    val skSpec = new SecretKeySpec(keyBytes, "AES")
    val iv = new IvParameterSpec(inputArr.slice(0, blockSize).toArray)
    val dataToDecrypt = inputArr.slice(blockSize, inputArr.size)
    cipher.init(Cipher.DECRYPT_MODE, skSpec, iv)
    new String(cipher.doFinal(dataToDecrypt.toArray))
  }
}</code>

Demo:

For demonstration purposes, let's encode the string "test text 123" with the encryption function written in Go and decode it with the decryption function written in Java (or Scala):

// Go encoder
key := []byte("0123456789abcdef")
text := "test text 123"
encryptedText := encrypt(key, text)
println(encryptedText) // prints c1bpFhxn74yzHQs-vgLcW6E5yL8zJfgceEQgYl0=

// Java decoder
byte[] keyBytes = "0123456789abcdef".getBytes();
String decodedText = AesDecrypter.decode(encryptedText, keyBytes);
System.out.println(decodedText); // prints test text 123

// Scala decoder
val decodedText = AesDecrypter.decode(encryptedText, "0123456789abcdef")
println(decodedText) // prints test text 123

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