Differentiation Features of RFID Systems - RFID: Fundamentals and Applications in Contactless Smart Cards and Identification - page 27

set equal to zero, meaning that even a cheap low-end system without security logic
can be used.
Our second example is a ticketing system for use in public transport. Such a system,
primarily data carriers in the form of contactless smart cards, is accessible to anyone.
The circle of potential attackers is thus enormous. A successful attack on such a
system could represent large-scale financial damage to the public transport company
in question, for example in the event of the organised sale of falsified travel passes,
to say nothing of the damage to the company's image. For such applications a high-
end transponder with authentication and encryption procedures is indispensable. For
applications with maximum security requirements, for example banking applications
with an electronic purse, only transponders with microprocessors should be used.
2.5.4 Memory capacity
The chip size of the data carrier — and thus the price class — is primarily determined
by its memory capacity . Therefore, permanently encoded read-only data carriers are
used in price-sensitive mass applications with a low local information requirement.
However, only the identity of an object can be defined using such a data carrier.
Further data is stored in the central database of the controlling computer. If data is
to be written back to the transponder, a transponder with EEPROM or RAM memory
technology is required.
EEPROM memories are primarily found in inductively coupled systems. Memory
capacities of 16 bytes to 8 Kbytes are available.
SRAM memory devices with a battery backup, on the other hand, are predominantly
used in microwave systems. The memory capacities on offer range from 256 bytes to
64 Kbytes.