Protocols for Secure Communication in Wireless Sensor Networks

2.4. Related Device Types 29
ports are being tagged. Since RFID tags can be accessed through a concealed,
wireless connection, people can be potentially tracked using the tags that are
embedded in their clothing and other personal items. By associating the identifiers
of RFID tags with the identity of a person, this person can be recognized
whenever one of the tags is detected. This leads to even better tracking capabilities
than with biometric recognition techniques, as not even physical contact
or a good view on a person is necessary for recognition.
Consequently, there are different views on RFID security. The first is from
the system operator’s point of view, where RFID tags are used as authentication
tokens. Here, security concerns exist regarding the clonability of tags, or other
manipulations that would yield illegitimate authorization. Also, the channel
between the reader device and the tag is a potential target for attacks. These
security issues are equivalent to those concerning the use of smart cards. As
the circuitry of an RFID tag is often much simpler than that of a smart card,
novel techniques are researched that offer certain security guarantees.
The second view on RFID security regards the tag itself as a risk as it allows
identification, and thus poses a potential threat to privacy. It is therefore crucial
to restrict access to the tag in such a way that the user has to agree on its
use before it can be accessed. For passports, this may be achieved by using a
metallic cover that shields the tag as long as the passport is closed. Another
approach is the use of a key that is required to access the data stored on the
RFID tag. This key can be determined from the optically readable data that is
printed in the passport (personal data of the passport holder, passport number).
Thus, a reader device with optical access to the passport can also read the data
from the RFID tag [67]. Whenever the passport is handed to somebody, for
example a customs officer, the right to access the RFID tag is implicitly granted.
2.4.3 Embedded Computers
As mentioned above, embedded microprocessors make up for the majority of
all microprocessor sales. It is estimated that on average a household in the U.S.
owns approximately 60 microcontrollers [76]. Most of these computers are not
networked in any way. They simply function as controllers for their containing
device, for instance a car engine or a washing machine. Making such devices
connected to their environment to other devices has just been started. One such
example is the registration of trucks on highways in Germany for road billing,
where so-called “on-board-units” that are installed in trucks communicate with
by-road stations for automated billing and can also be queried by mobile checking
teams [29].