Key Management - Codes: The Guide to Secrecy from Ancient to Modern Times - page 242

6.3 Secure Electronic Transaction (SET)

To travel hopefully is better than to arrive, and the true success is to labour.
Robert Louis Stevenson (1850-1894), Scottish novelist

On page 232, we mentioned the circumstances surrounding how Visa and
MasterCard developed SET in 1997. Now we have the tools to describe this
scheme in detail. To do so, we need some terminology, and due to the complexity
of the scheme, a brief overview before we give the complete description.
First of all, a payment gateway is an interface between SET and the existing
e-commerce network for authorization and payment. We will use Trent for this
role. Alice will be our cardholder, and Bob will be our merchant. Diagram 6.1
is an illustration of the SET mechanism after which we will explain the opera-
tion in detail. However, it will be a simplified version to ease the explanation
without significantly altering the themes and function of the SET protocols.
For instance, in the following we assume that Trent is internally contacting the
acquirer (a financial institution that processes credit card payments and autho-
rizations), and an issuer (a bank that provides Alice with her card), without
mentioning them, except parenthetically.

Diagram 6.1 SET Protocol Actions

Trent
Payment
Gateway

Alice
Cardholder

Bob
Merchant

Purchase
−−−−−−−→
Request

Authorization
−−−−−−−−−−→
Request

Verify Verify

Purchase
←−−−−−−−
Response

Authorization
←−−−−−−−−−−
Response

Verify

Encrypt

Payment Capture
−−−−−−−−−−−−−→
Request

Sign & Decrypt

& Verify

Payment Capture
←−−−−−−−−−−−−−
Response

Send Goods
←−−−−−−−−−
or Services

Transfer
Funds

Bob's
Bank
Account