.. _common_parameters:

Common Parameters
~~~~~~~~~~~~~~~~~

These parameters are always mandatory:

``cp``
  **Merchant id** which you get from your LaterPay merchant backend, which
  matches your API key.

``hmac``
  **URL signature** (see :ref:`Signing URLs <signing_urls>`).

``ts``
  The current time as a number of seconds since the Unix epoch
  (1970-01-01T00:00:00Z) formatted as an integer. It should be set to the
  value when the user made the request.

  Example: ``"1325408400"`` is ``"Jan 1st 2012, 09:00am"``. This is used to
  ensure that your API calls are "fresh", preventing someone attempting to
  store and re-use a signed URL later.