CODEWITHSUNDEEP
javanode.jsencryptionsecure-codingcode-security
Jyubin Patel
Jyubin Patel

Reputation: 1373

Getting some error while decrypting text in Java

I have below NodeJS code for decryption and it is working perfectly fine but when I am trying to convert the same code in Java at that time I am getting below error.

Given final block not properly padded. Such issues can arise if a bad key is used during decryption

Node JS code snippet:

  let textParts = text.split(':');
  let iv = Buffer.from(textParts.shift(), 'hex');
  let encryptedText = Buffer.from(textParts.join(':'), 'hex');
  let decrypted = decipher.update(encryptedText);
  let decipher = crypto.createDecipheriv(
    'aes-256-cbc',
    Buffer.from(ENCRYPTION_KEY),
    iv,
  );
  decrypted = Buffer.concat([decrypted, decipher.final()]);
  return decrypted.toString();

Java code snippet:

try {
    IvParameterSpec iv = new IvParameterSpec(initVector.getBytes(StandardCharsets.UTF_8));
    SecretKeySpec skeySpec = new SecretKeySpec(key.getBytes(StandardCharsets.UTF_8), "AES");
    Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
    cipher.init(Cipher.DECRYPT_MODE, skeySpec, iv);
    byte[] original = cipher.doFinal(Base64.decodeBase64(encyptedData));
    return new String(original);
} catch (Exception ex) {
    ex.printStackTrace();
}

Encryption Key is same for both Node JS and Java code. Thanks in advance.

Upvotes: 0

Views: 706

Answers (2)

Anup Ganatra
Anup Ganatra

Reputation: 366

If your initial vector is 32 bytes then you need to decrypt as below.

public String decrypt(String encryptedData) {
    try {
        String data[] = encryptedData.split(":");
        IvParameterSpec iv = new IvParameterSpec(getBytes(data[0]));
        Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
        SecretKeySpec skeySpec = new SecretKeySpec(YOUR_KEY.getBytes(), "AES");
        cipher.init(Cipher.DECRYPT_MODE, skeySpec, iv);
        byte[] decryptedData = cipher.doFinal(getBytes(data[1]));
        return new String(decryptedData);
    } catch (Exception e) {
        throw new RuntimeException("Error occured while decrypting data", e);
    }
}

public byte[] getBytes(String s) {                   
    String tmp;
    byte[] b = new byte[s.length() / 2];
    int i;
    for (i = 0; i < s.length() / 2; i++) {
        tmp = s.substring(i * 2, i * 2 + 2);
        b[i] = (byte)(Integer.parseInt(tmp, 16) & 0xff);
    }
    return b;
}

Upvotes: 1

hamed
hamed

Reputation: 1

it seems the problem is with size of the variabel in java when you decode. Check this links maybe those give you some hints :

1- ejava-base64-encode-and-decode

2- given-final-block-not-properly-padded

Upvotes: -2

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