public boolean verifyResponseCode(long challenge, String response)
      throws GeneralSecurityException {
    String expectedResponse = generateResponseCode(challenge, null);
    return expectedResponse.equals(response);
  }
@param challenge A challenge to check a response against
@param response A response to verify
@return True if the response is valid
java/com/google/android/apps/authenticator/otp/PasscodeGenerator.java