How to Decrypt AES-Encrypted Text in Java and Scala, Given Golang Encryption?

AES Encryption in Golang and Its Decryption in Java

The Golang encryption function for AES provided in the question encrypts a string using the Advanced Encryption Standard (AES) algorithm, producing a ciphertext in Base64 encoding. To decrypt this ciphertext in Java, we require an appropriate decryption function.

Java Decryption Function

<code class="java">import java.util.Base64;
import javax.crypto.*;
import javax.crypto.spec.*;

public class AESDecryption {

    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);
    }

    public static void main(String[] args) {
        // Encryption result from the Go function.
        String base64Text = "c1bpFhxn74yzHQs-vgLcW6E5yL8zJfgceEQgYl0=";
        // The encryption key (same as in Go).
        byte[] key = "0123456789abcdef".getBytes();

        try {
            // Decrypt the ciphertext.
            String decrypted = decode(base64Text, key);
            // Print the decrypted text.
            System.out.println(decrypted);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}</code>

Scala Decryption Function

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

object AESDecryption {

  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), StandardCharsets.UTF_8)
  }

  def main(args: Array[String]): Unit = {
    // Encryption result from the Go function.
    val base64Text = "c1bpFhxn74yzHQs-vgLcW6E5yL8zJfgceEQgYl0="
    // The encryption key (same as in Go).
    val key = "0123456789abcdef"

    // Decrypt the ciphertext.
    val decrypted = decode(base64Text, key)
    // Print the decrypted text.
    println(decrypted)
  }
}</code>

Both the Java and Scala decryption functions take the ciphertext and key as input, decrypt the ciphertext using the AES/CFB/NoPadding algorithm, and return the decrypted plaintext as a string.

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