Applications and the Future - Codes: The Guide to Secrecy from Ancient to Modern Times - page 354

cryptographic coprocessor is typically added to the architecture, thereby
reducingcryptographic calculations to a few hundred microseconds.
Types 1-3 are often grouped under the single heading of memory cards and
type 4 under the headingof microprocessor chip cards . Memory cards are, nat-
urally, the least expensive and most common. They contain what is called Elec-
tronically Erasable Programmable Read-Only Memory (EEPROM) nonvolatile
memory. 9.27 For security, the data may be locked in by a PIN of up to eight
digits written to a special file on the card.
Chips : There are three kinds of smart card chips as follows.
1. Memory Chips : Naturally, the most basic and least expensive are those
chips that merely store data and have no processingcapabilities. Once
created, memory chips cannot be reprogrammed, since they can only hold
static data such as personal information that does not require dynamic
encipheringcapacity. To chane the capacity of such a memory card, it
would need to be replaced entirely.
2. Applications Specific Integrated Circuits (ASIC) : The ASIC chips
are hard-wired to keep data and execute a specific processingjob. Of
course, this processingcapacity makes the ASIC chip stroner than the
memory chip. Yet, the ASIC chip cannot be reprogrammed, as is the case
with the memory chip. However, the ASIC chip does allow for some static
encryption, but this is suitable only for low-level security applications.
3. Microprocessor Chips : These chips are the most powerful and versatile
of the three types. They cannot only do what both the memory and ASIC
chips can do, but also they are capable of dynamic encryption, and they
can be reprogrammed or updated, unlike the previous two. Processor
cards have microprocessor chips that typically come in 8-, 16-, or 32-bit
formats. Their data storage may range from 300 to 32,000 bytes.
Microprocessor-based smart cards have the benefits of (1) a high level of
security, havingthe capacity to execute PKC or SKC protocols, including
DES, RSA, and ECC; (2) multiple applications on the same card; and (3)
ease of updatingexistingapplications, or the addition of new ones.
Microprocessor cards have numerous applications: the access medium for
GSM (see page 347); for identification; for electronic signatures; for access
to restricted areas; to pro tect data storage; and for e-commerce.
9.27 Nonvolatile memory means any kind of solid-state memory that does not lose its contents
when the computer is turned off. In the case of a memory card, when it is removed from the
card reader, the power is cut off, yet the card stores the data. On the other hand volatile
memory loses its contents when the computer is turned off. Nearly all RAM is volatile, except
of course, battery-powered RAM. Included under the heading of nonvolatile memory are not
only EEPROM, but also all other forms of ROM such as programmable read-only memory
(PROM), erasable programmable read-only memory (EPROM), and flash memory, sometimes
called flash RAM . The latter type of memory can be erased and reprogrammed. The term
“flash” is derived from the fact that in a microchip, a section of memory cells is erased in one
solitary act, in a flash . Flash memory is employed in PC cards, digital cell phones, printers,
and digital cameras, for example.