Client opens an account
Client receives a certificate
Merchants have their own certs
The client places an order (C M)
The merchant is verified (M C)
The order and payment are sent (C M)
The merchant requests payment authorization (M PG)
Payment is approved (PG I, I A, I,A PG)
The merchant receives authorization response (PG M)
The merchant confirms the order (M C)
The merchant provides goods or service (M C)
The merchant requests payment (M A)