package expressCheckout;

import java.util.logging.Level;
import java.util.logging.Logger;
import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import org.json.JSONException;
import org.json.JSONObject;

/**
 * DecryptParameters decryption class
 *
 * @author Mula
 */
public class DecryptParameters {
  /**
   * Define the your IV and Secret Key.
   */
  static String IV = "******";
  static String encryptionKey = "*******";

   /**
    * Main function.
    *
    * @param args the command line arguments
    */
   public static void main(String[] args) {
     try {
       // Get the encrypted string from the payload during the callback.
       String encryptedString = "**********************";

       // Instead consume the parameter object as you may wish.
       System.out.println(decrypt(hexToBytes(encryptedString), encryptionKey));
     } catch (JSONException ex) {
       Logger.getLogger(DecryptParameters.class.getName()).log(Level.SEVERE, null, ex);
     } catch (Exception ex) {
       Logger.getLogger(DecryptParameters.class.getName()).log(Level.SEVERE, null, ex);
     }
   }

   /**
    * Convert string to byte
    *
    * @param string String
    *
    * @return data byte[]
    */
   public static byte[] hexToBytes(String string) {
     if (string == null) {
       return null;
     } else if (string.length() < 2) {
       return null;
     } else {
       int len = string.length() / 2;
       byte[] buffer = new byte[len];
       for (int i = 0; i < len; i++) {
          buffer[i] = (byte) Integer.parseInt(string.substring(i * 2, i * 2 + 2), 16);
       }
       return buffer;
     }
   }

   /**
    * Decrypt the encrypted bytes to string
    *
    * @param cipherText byte[]
    * @param encryptionKey String
    *
    * @return string String
    * @throws java.lang.Exception
    */
   public static String decrypt(byte[] cipherText, String encryptionKey) throws Exception {
     Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding", "SunJCE");
     SecretKeySpec key = new SecretKeySpec(encryptionKey.getBytes("UTF-8"), "AES");
     cipher.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(IV.getBytes("UTF-8")));
     return new String(cipher.doFinal(cipherText), "UTF-8");
   }
}