code: public static String encipher(String key, String clearText) {
          if (key == null) {
              throw new NullPointerException("key may not be null");
          }
  
          if (key == "") {
              return clearText;
          }
  
          if (clearText == null) {
              return null;
          }
  
          byte[] keyBytes = convertKeyToByteArray(key);
          byte[] clearTextBytes = convertClearTextToByteArray(clearText);
          byte[] cipherBytes = applyCipher(keyBytes, clearTextBytes);
          return Base64.encodeToString(cipherBytes);
      }
docs: Use the key to produce a ciphered String from the clearText.