WHAT CAN RFID DO FOR VANETS?
A Cryptographic Point of View
J. Munilla, A. Ortiz and A. Peinado
Dept. of Ingenieria de Comunicaciones, E.T.S. Ingenieria de Telecomunicacion, Universidad de Malaga, Málaga, Spain
Keywords: RFID security, VANET, Authentication, Traffic safety.
Abstract: Vehicular ad hoc networks (VANETs) are becoming more popular as a way to increase the traffic safety and
comfort. The inclusion of RFID technology in the VANETs architecture could enable the development of
interesting new services and improve the overall results. However, in addition to the typical problems of
RFID systems, new challenges arise in this scenario (RFID-VANETs) that must be solved. This paper
analyzes the security aspects of these applications.
1 INTRODUCTION
Nowadays, vehicular ad-hoc networks are presented
as a new generation of networks oriented to improve
the safety and driving comfort. These networks
allow connectivity among mobile hosts. This way,
vehicles in a VANET can share information to each
other in a short range by using the 802.11p wireless
technology. The use of a light infrastructure or a
backup network can improve the services offered in
a VANET providing the so called vehicle-to-
infrastructure communication (V2I) (Hartong,
2007). This infrastructure is not only composed by
802.11p base stations but, there are several
approaches proposing the use of a RFID (Radio
Frequency Identification) infrastructure (Lee, 2009)
for many purposes such as positioning or traffic
signals identification. Thus passive RFID tags can
be used as information sources at different points
such as traffic signs (Ortiz, 2010). The advantage of
this option is that they do not require a power
source, reducing the maintenance and thus the global
cost of the system.
In vehicular applications, RFID is typically used
in a scenario where the tag is located on the vehicle
and the reader is placed on the road. Tags are usually
read statically, since the vehicle will stop over the
reader. Bus tracking is a typical application using
this scheme (Lee, 2009). Most of these applications
belong to the comfort category.
In VANETs there are two different types of
information that can be used to improve the traffic
safety. The first corresponds to information coming
from other vehicles regarding traffic congestion
status or accident alerting. The second corresponds
to environmental information coming from traffic
signs, speed limits, motorway tolls or semaphores.
The use of RFID technology to collect
environmental data requires reading tags deployed
on the road and the reader to be located on the
vehicle. The RFID infrastructure consists of a series
of RFID tags located at any signalling point. So, the
tags have to contain information regarding the point
in which they are located (i.e. a speed limit, a
dangerous bend, etc.). Most of these applications
belong to safety-related category of VANET
applications.
This paper focuses on the security issues related
to the use of RFID on vehicular applications. Section
2 shows the state of the art of RFID on vehicular
applications. Section 3 depicts future uses. Section 4
analyses the security requirements for RFID in
VANETs. Section 5 discusses the Security and
feasibility of secure RFID-VANETs architectures
and finally Section 6 concludes.
2 PAST AND PRESENT OF RFID
FOR TRAFFIC USE
Electronic Toll Collection (ETC) has been until not
long ago the main use of RFID for traffic. Since
1992 active RFID tags have been used in vehicles to
automate the toll process. These tags, mounted
internally (windshield) or externally (near the plate),
295
Munilla J., Ortiz A. and Peinado A. (2010).
WHAT CAN RFID DO FOR VANETS? - A Cryptographic Point of View.
In Proceedings of the International Conference on Security and Cryptography, pages 295-298
DOI: 10.5220/0002929502950298
Copyright
c
 SciTePress

allow an automated toll process where the vehicles
can proceed without stopping to pay at the
tollbooths. Theses system consist of three basic
parts: the automatic vehicle classification based on
sensors that count the number of axles, the automatic
vehicle identification which uses RFID tags, and the
violation enforcement where cameras are used to
identify evaders.
The distance between the overhead antenna in
the ETC facility and the tag of the vehicle is around
a few meters and, thus the operating frequencies for
these applications are usually UHF or microwave
(Europe EN 300 440). .
For instance EZ-Pass on the east coast of the
United States, Fast-Track on the east coast and
SunPass in Florida, use active UHF RFID tags for
vehicle identification. As mentioned, the batteries of
these active tags need to be replaced after one or two
years. Although these active tags are not power
constrained and probable secure cryptographic
solutions could be implemented, some researches
have proved that these tags provide little or not
security (Green, 2008).
Other uses of RFID tags in relation to the
vehicles but not so much to the traffic is the use of
cards to pay in gas stations and as vehicle anti-theft
systems (immobilizer). These cards work usually in
HF and provides high standard of security. However,
there have also been famous cases of attacks; e.g. the
security of the DST (Digital Signature Transponder)
manufactured by Texas Instrument, with key lengths
of only 40 bits, and used by millions of customers
was defeated by performing reverse engineering and
key cracking (Bono, 2005).
3 RFID IN FUTURE VANETS
RFID technology can be easily integrated in
vehicular networks as it provides a low cost solution
for V2I communications. The RFID applications
currently in use employ this type of communication.
European Union is working in RFID tracking
systems to issue automated tickets for minor traffic
violations (Asset, 2010), as an application of the
Electronic License Plate. Other proposals describe
automatic payment systems of parking-fess, or
traffic-light priority systems for easing traffic
congestion and reducing road accidents (Lee, 2009),
but all of them with the same architecture: tag on
vehicles and reader on the road.
Since RFID technology deals with identification
and authentication, it represents a further step in the
information collection systems. This way, RFID
constitutes an alternative mechanism for I2V
(infrastructure to vehicle) communication with
important advantages.
Low cost of this technology allows the system to
disseminate a huge number of tags to complement
traditional traffic signalling. The information
obtained from RFID tags can be considered as local
meaning information due to the reading coverage
limitations of this technology. The infrastructure
gains a real advantage since a new non-attending
signalling system can be deployed. This signalling
system will always work under extreme conditions
such us VANET loss connection or bad weather
conditions (reduced visibility). Safety-related
applications, such us collision avoidance,
cooperative driving, traffic optimization, lane-
changing assistance or road conditions warnings,
may be implemented.
RFID signalling may be implemented as a
complementary support of the existing technologies.
In this way, the information collected from different
means can be analysed to obtain trusted and more
accurate information. Other I2V applications, such
as collision avoiding system in urban intersections or
wrong way detection system, may be implemented
by means of RFID technology.
Some constraints exist when we try to implement
this technology: mainly, the speed of vehicles.
Several initiatives including tag on vehicle
architectures have been previously published with
different objectives in mind (Lee, 2009), (Penttila,
2004), (Chon, 2004). The experimental results state
the maximum speed at 100 Km/h, with a high error
rate in readings.
Although these results allow the utilisation of
this architecture in reduced speed areas, such as
urban roads, much more research must be applied.
The most important constraint is the reading range
and the total reading time which includes activation
time and transmission time.
However, none of these proposals have taken in
mind security requirements to allow a secure and
trusted utilisation of the system. In the next section,
we analyse these proposals from a cryptographic
point of view.
4 SECURITY REQUIREMENTS
The main problems about security in RFID reside in
privacy and authentication (Juels, 2006). Privacy
must be applied to avoid physical tracking attacks,
where a forge reader can interrogate a legal tag
without the knowledge of its owner. Authentication
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allows readers and tags to verify the real identity of
each other. However, depending on the specific
application the security requirements may be
modified (Avoine, 2005).
Two scenarios are considered: tag on vehicles
and reader on vehicles.
Tag-on-vehicle Architecture. In these situations the
reader is connected to a backend server or central
database while the tags are attached to vehicles. This
configuration allows the reader to make hard
computations with the help of the server. Thus the
limitation of this architecture resides in the tag.
Vehicles speed is not a problem for these
applications as the vehicles (and hence the tags)
interact with the reader at very low speed or when
they are completely stopped.
Taking in mind all these features, the security
requirements for these applications are practically
the same of that for a traditional RFID system, and
hence, the protocols proposed for RFID may be
applied in most situations.
Reader-on-vehicle Architecture. This architecture
corresponds to future or recently proposed
applications where the main objective is related to
traffic safety. These applications use RFID tags to
get information from the road, where the tags are
located. It is important to note that this architecture
presents severe limitations derived from the
simplicity of tags (as any other RFID application)
and the connectivity restriction of the readers. The
connectivity depends on the VANET instant
behaviour and range. Another relevant restriction
comes from the high speed of vehicles during the
identification process. As a consequence, most of the
protocols proposed in the literature are not suitable
for this scenario. The security requirements for this
architecture are the followings.
Confidentiality. It is not necessary as those
applications provide information about road
conditions. This is the general criteria applied to
safety-related applications (Yousefi, 2006).
Untraceability. Since the tags are located on a
fixed place on the road, traceability does not
constitute a problem. This fact simplifies notably the
identification protocols.
Authentication. It is mandatory. The main risk
resides in the possibility that an attacker inserts fake
tags on the road producing fake readings.
Authentication scheme must be resistant to reply
attacks and tag-cloning attacks.
Non-repudiation. This is not a requirement for
this kind of application.
Availability. Availability is not the main concern
provided that RFID is not the unique mechanism on-
board to get road information.
5 OPTIONS AND FEASIBILITY
Security requirements for tag-on-vehicle
architectures coincide with that of traditional RFID
systems. For this reason the only applications
currently in use are based in this architecture. In
spite of that, many of these applications do not apply
security mechanisms or apply very low level
security, such us toll collection systems described in
section 2.
Security requirements for reader-on-vehicle
architectures apparently simplify the RFID
identification schemes as only authentication is
mandatory and anti-collision is not necessary.
However, the existing protocols can not be applied
due to constraints imposed by vehicle speed, reading
range and reader connectivity lack. Furthermore,
although transmission time is short, it is important to
note that any attacker can interrogate a tag for
undefined time because the tags are located on the
road with no physical access restriction.
Cryptographic tags may be divided into two
categories: symmetric-key tags and asymmetric-key
tags. Symmetric-key tags are not suitable because
the key management is too complex. The number of
tags to authenticate is too high, and the readers on
vehicles must know all the secret keys. Remember
that the reader have no permanent connection with
the backend server.
A special type of asymmetric-key cryptosystems
is the identity-based encryption and signature,
particularly designed to reduce the global
complexity using the own identification data (such
as the email address) instead of digital certificates as
a public key for encryption and signature
verification (Baek, 2004). In (Liang, 2008), it is
proposed an implementation of identity-based
encryption and signature in RFID systems. The
implementation of these schemes requires the
existence of a central trusted server (PKG). PKG
first generates its master (private) and public key
pair. Then the PKG generates the private key of
every user associated with his identity. In the case of
RFID systems, this key may be loaded in each tag
and reader prior to the system deployment. The main
advantage of these schemes resides in the
mechanism to obtain the public key of another user.
In traditional asymmetric schemes, public keys must
be retrieved from a public repository. In identity-
WHAT CAN RFID DO FOR VANETS? - A Cryptographic Point of View
297

based encryption, every user can generate the public
key of another user employing the identifying
information of the receiver (for encryption) or the
signer (for signature) and the public key of the PKG.
Hence, no connection has to be established to verify
the signatures sent by the tags. Thus, identity-based
encryption and signature seem to be the most
suitable schemes to this architecture, although more
research has still to be applied because identity-
based cryptography is based on asymmetric-key
cryptosystems, and its computational complexity
must be taken in mind
6 CONCLUSIONS
The feasibility of RFID applications in VANETs has
been analysed from a cryptographic point of view. In
addition to the typical problems of RFID systems,
new challenges arise in this scenario (RFID-
VANETs) that must be solved. A classification of
RFID-VANET applications is presented based on
the reader-tag architecture, resulting in two
categories: tag on vehicles architectures, similar to
traditional RFID systems, and reader on vehicles
architectures, with new challenges to solve. Most
relevant guidelines to secure this kind of systems
have been presented, since currently, most RFID
systems can be characterized by an important
security lack.
ACKNOWLEDGEMENTS
This work has been partly supported by the Spanish
Ministry of Science and Innovation and the
European FEDER funds under project TIN 2008-
02236/TSI.
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