This scenario is similar to scenario 4. The same two parties, buyer and seller, wish to perform a transaction. In this case, however, each authenticates to a third-party security service responsible. The buyer and seller exchange authentication data provided by their security systems to authenticate the transaction. Back Office Transaction, Third Party Security Service.
Buyer authenticates with security service.
Security service provides authentication document to buyer. Seller authenticates with security service. Security service provides authentication document to seller. Buyer and seller execute transaction, providing authentication documents to each other. Authentication documents include authz attributes and authn event description.