Once authorized by the user with Touch ID, your app receives a payment token from PassKit.
The payment token encapsulates the information needed to complete a payment transaction. It
includes a cryptogram, unique to the specific purchase, that can be decrypted with your private
key or when the payment information is transmitted to a payment processor’s server that has
your private key.
Figure 2 illustrates a typical payment flow. First the app checks that it can offer Apple Pay as a
payment method. In this example, the app needs the postal code from the selected shipping
address to calculate shipping cost and update the total amount due. When the user authorizes
payment, your app receives a payment token from the Secure Element, via PassKit.
Finally the app calls appropriate APIs in the payment processor SDK to pass the payment
information to the payment processor, they process the transaction.