Given Final Block not properly padded while AES decryption

Question

First, I\'ll tell what is my primary goal. I\'m going to use AES to encrypt some content in the client side, then use RSA public key to encrypt the important AES specs and s

Answer 1

Thanks to Artjom B.

Solution : Working Code

Javascript / Client Code

Server / Java Code

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.Key;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.KeyGenerator;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

// You have to download and add it into your project, others are Java Inbuilt Libraries
// Do not use sun.misc for Base64 functions
import org.apache.commons.codec.binary.Base64; 

public class BasicDecryption {

//I've done it in post method of servlet

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    String encryptedData = request.getParameter("cipherData");
    String data[] = encryptedData.split(":");
    String iv = data[0];
    byte[] encryptedByteData = hexStringToByteArray(data[1]);
    String keyString = data[2];

    IvParameterSpec iv = new IvParameterSpec(Base64.decodeBase64(iv);
    Key k = new SecretKeySpec(Base64.decodeBase64(keyString),"AES");

    try {
        System.out.println("Decrypted String:"+BasicDecryption.decrypt(Base64.encodeBase64String(encryptedByteData),k,iv));
    } catch (InvalidKeyException | NoSuchAlgorithmException
            | NoSuchPaddingException | IllegalBlockSizeException
            | BadPaddingException | InvalidAlgorithmParameterException e) {
        e.printStackTrace();
    }
}

public static final String decrypt(final String encrypted,final Key key, final IvParameterSpec iv) throws InvalidKeyException,
NoSuchAlgorithmException, NoSuchPaddingException,
IllegalBlockSizeException, BadPaddingException, IOException, InvalidAlgorithmParameterException {

      Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
      cipher.init(Cipher.DECRYPT_MODE, key,iv);
      byte[] raw = Base64.decodeBase64(encrypted);
      byte[] stringBytes = cipher.doFinal(raw);
      String clearText = new String(stringBytes, "UTF8");
      return clearText;
}

public static byte[] hexStringToByteArray(String s) {

    int len = s.length();
    byte[] data = new byte[len / 2];

    for (int i = 0; i < len; i += 2) {
        data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4)
                + Character.digit(s.charAt(i+1), 16));
    }
    return data;
}
}