An access control system for signal processing applications includes an integrated circuit (IC) card, or "smart" card, that provides both security control and data descrambling functions. A security control processor in the smart card IC performs functions such as entitlement management and key generation. The smart card IC also includes a descrambler for processing data, such as video data, at high data rates. Mechanical characteristics of the smart card satisfy the ISO standard 7816-1. In addition, the interface to the smart card is via eight-terminals arranged on the surface of the card in accordance with ISO standard 7816-2. The eight terminal interface provides both high speed data I/O (input and output) required for data descrambling and ISO standard low speed serial data I/O.