AES Encryption in Golang and Decryption in Java

Question

I have the following AES Encryption function written in Golang.

func encrypt(key []byte, text string) string {
    plaintext := []byte(text)

    block, err          


        

Answer 1

Java decoder (see also online runnable demo, open and click "Execute"):

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);
}

Kevin in comments has offered this demo of the original Go encoder, where we can see the result of:

encrypt([]byte("0123456789abcdef"), "test text 123")

is c1bpFhxn74yzHQs-vgLcW6E5yL8zJfgceEQgYl0=.

Let's see how the Java decoder above deals with that input:

String text = "c1bpFhxn74yzHQs-vgLcW6E5yL8zJfgceEQgYl0=";
byte[] key = "0123456789abcdef".getBytes();
System.out.println(decode(text, key));

Prints test text 123 ✔

---

Scala version (online runnable demo):

def decode(input:String, key: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))
}

def main(args: Array[String]) {
    print(decode("c1bpFhxn74yzHQs-vgLcW6E5yL8zJfgceEQgYl0=", "0123456789abcdef"));
}

I think the only error in the Scala version is using Hex.decodeHex. You need a Base64 decoder that uses the URL-safe alphabet as described in RFC 4648, which java.util.Base64 offers (since Java 8) with its getUrlDecoder().