Smart cards provide very high security and flexibility in subscribers management
Patrice Peyret, G. Lisimaque, T.Y. Chua · IEEE Transactions on Consumer Electronics · 1990
It is pointed out that in smart-card-based pay television, the security secrets reside solely in inexpensive and easily replaceable plastic cards-the same size as a credit card, with a secure computer microchip. The decoder no longer holds any secrets. Replacement smart cards can be sent to each subscriber periodically, or whenever there is reason to believe the system security has been breached. With each batch of new cards, algorithms or secret keys can be changed. Attacks on security are therefore extremely difficult to organize, and are not economically viable.>