Also, and perhaps most important, the stored data can be protected against unauthorized access and tampering. Memory functions such as reading, writing, and erasing can be linked to specific conditions, controlled by both hardware and software. Another advantage of smartcards over magnetic stripe cards is that they are more reliable and have longer expected lifetimes. Memory Cards Though referred to as smartcards, memory cards are typically much less expensive and much less functional than microprocessor cards. In the simplest designs, logic exists to prevent writing and erasing of the data.
More complex designs allow for memory read access to be restricted.
Typical memory card applications are pre-paid telephone cards and health insurance cards. Typical conventional smartcard architectures have properties reflected in Table 17-1. Though the chip can be thought of as a tiny computer, the external terminal must supply the voltage, ground, and clock. Though technically these are in the category of microprocessor cards, they are separated here because of differences in cost and functionality. However, if a cryptographic coprocessor is added to the architecture, the time required for this same operation is reduced to around a few hundred microseconds.