Computing the IPN signature

The signature is computed by following the same procedure as for creating the payment form.

The data submitted by the payment gateway is encoded in UTF-8. Any alteration of received data will result in signature computation error.

You must compute the signature with the fields received in the notification and not the ones that you transmitted in your payment form.

To compute the signature:

  1. Take all the fields whose name starts with vads_.
  2. Sort these fields alphabetically.
  3. Concatenate the values of these fields separating them with the "+" character.
  4. Concatenate the result with the test or production key separating them with a "+".
  5. According to the signature algorithm defined in your shop configuration:
    1. if your shop is configured to use "SHA-1", apply the SHA-1 hash function to the chain obtained during the previous step.
    2. if your shop is configured to use "HMAC-SHA-256", compute and encode in Base64 format the message signature using the HMAC-SHA-256 algorithm with the following parameters:
      • the SHA-256 hash function,
      • the test or production key (depending on the value of the vads_ctx_mode field) as a shared key,
      • the result of the previous step as the message to authenticate.