Scenario: Selective signing and encrypting

BookStore creates a form that will be filled in by Alfred and sent on to EasyPay.

  1. BookStore signs all of the form except for shipping address and credit card information, which is filled in by Alfred.
  2. Alfred fills in the form, encrypts the payment authorization element in a key shared with EasyPay, signs and returns it to BookStore.
  3. BookStore processes the form and confirms the integrity of the order (the book title and price) and passes the encrypted credit card info to EasyPay.