Security in Vehicular Ad Hoc Networks through Mix-Zones Based Privacy

International Journal of Science and Research (IJSR), India Online ISSN: 2319-7064
Volume 2 Issue 9, September 2013
www.ijsr.net
Security in Vehicular Ad Hoc Networks through
Mix-Zones Based Privacy
1
S. Kavitha, 2
M. Parveentaj
Research Scholar, Sri Jayendara Saraswathy Maha Vidayala College of Arts and Science, Coimbatore- 05, India
M.C.A., ADCA, M. Phil, Assistant Professor,
Sri Jayendara Saraswathy Maha Vidayala College of Arts and Science, Coimbatore- 05, India
Abstract: Vehicular Networks (VNs) seek to provide, among other applications, safer driving conditions. Vehicles need to periodically
broadcast safety messages providing precise position information to nearby vehicles. Recent advances in development of Wireless
Communication in Vehicular Adhoc Network (VANET) has provided emerging platform for industrialists and researchers. Vehicular
adhoc networks are multi-hop networks with no fixed infrastructure. As a result, the driver’s privacy is at stake. In order to mitigate this
threat, while complying with the safety requirements of VNs, the creation of mix-zones security at appropriate places of the VN to
prevent the attacks Vehicle. Propose to do so with the use of cryptography algorithm AES with zone based routing protocol, analytically
how the combination of mix-zones into mix-networks brings forth location privacy in vehicle node. Finally, show by simulations that the
proposed zone based security is effective in various scenarios.
Keywords: Vehicular Networks, VANET, AES, Cryptography Algorithm
1. Introduction
Vehicular Networks (VNs) consist of vehicles and Road
Side Units (RSUs) equipped with radios. Using Vehicle-to-
Vehicle (V2V) and Vehicle-to-Infrastructure (V2I)
communications, vehicles share safety-related information
and access location-based services. Initiatives in Europe [6]
and the US [8] are evaluating VNs promises of safer driving
conditions and more efficient traffic management.
Envisioned safety-related applications require the vehicles to
periodically broadcast their current position, speed and
acceleration in authenticated safety messages. This
messaging increases the awareness of vehicles about their
neighbours’ whereabouts and warns drivers off dangerous
situations.
The nature of the wireless communications makes
eavesdropping particularly easy. All an adversary needs to
do is to deploy its devices across the area of the network that
it wishes to monitor. At the same time, safety messages
provide rich information on their senders, for example, the
vehicle's location. This essentially allows automatic tracking
of the vehicle whereabouts. Thus, it can reveal private
information regarding the activities of the driver. The wide
availability of VN-compatible radios (802.11-based) makes
such a threat even more credible.
The use of randomly changing identifiers (i.e., pseudonyms)
has been proposed to de correlate the identity of vehicles
from their locations. The purpose of such a scheme is to
achieve un link ability between the vehicle and its
pseudonyms in the long run. However, updating the
pseudonym of a vehicle in a monitored region is in effective,
because the location information of safety messages can still
be used for tracking. Therefore, changing pseudonyms is
effective only within regions in which monitoring is
impossible.
2. Problem Statement
Problem arises when one or more users try to inject false
information to the network. This information is very
important, and has a key role in driver’s decision making. A
proper decision is the result of proper information, and
improper information causes improper decisions. E. g. a
vehicle reports heavy traffic on a few miles ahead. But
maybe a malicious user wants to cheat others for some
selfish aims, e.g., to divert traffic from a given road and thus
free it for themselves or for entertainment. In such case it is
said that the security of VANETs is affected.
3. Related Works
Public key certificates are envisioned for this purpose. These
are electronic documents that link a public key with a
subject´s identity. However, using real or permanent identity
would allow tracking. As opposed from that, these
credentials should not make the vehicle to be completely
anonymous. Liability attribution is required by the legal
authority whenever misbehaviour (e.g. traffic offence, false
warning) is detected. These tradeoffs are called resolvable
anonymity. Two different mechanisms have been proposed
to satisfy this need in VANETs – identity-based
cryptography and pseudonymous short-lived public key
certificates. Although they are based on different
cryptographic techniques, their underlying processes of
creation and use are similar. We will focus on certificates as
it is the mechanism proposed in the security standard in the
area, IEEE 1609.2 (IEEE Computer Society, 2006).
Particularly, pseudonymous certificates allow providing both
authentication and privacy protection (Callandriello, G.
Papadimitratos, Lloy, & Hubaux, 2007). Readers interested
on identity-based cryptographic mechanisms can refer to
(Sun, Zhang, & Fang, 2007).
Vehicular contexts have an interesting feature related to
identity management. As opposed to classical computer
networks, in which no central registration exists, vehicles are
Paper ID: 12013148 115

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uniquely identified from the beginning. Indeed, this process
is performed by both manufacturers and the legal authority.
Manufacturers assign each vehicle a Vehicle Identification
Number (VIN). On the other hand, legal authorities require
vehicles to have a license plate. Both identifiers are different
by nature. Whereas VINs are intended to uniquely identify
manufactured vehicles, license plates are assigned to every
vehicle registered in an administrative domain. Thus, VINs
cannot be changed for a given vehicle, whereas license
plates can change over time. Moreover, license plates are
intended to be externally visible. This issue has an
immediate consequence related to privacy preservation -
vehicles are not completely anonymous, as visible tracking
is currently possible.
Figure 1: Alternatives to retrieve vehicular credentials
Pseudonymous certificates must be issued by a trusted
authority. A Vehicular Public Key Infrastructure (VPKI) is
often assumed for this purpose (Raya, Papadimitratos, &
Hubaux, 2006). Figure 2 shows its composition and its
relationships with other entities that were introduced on the
VANET model.
VPKI is composed by a set of Trusted Third Parties (TTPs)
in charge of managing pseudonymous certificates. It is
assumed to be structured hierarchically. There is a single
root Certificate Authority (CA) in each administrative
domain (e.g. a country) and a delegated CA in each region
within that domain. As vehicles from different regions (or
even domains) can encounter themselves in a VANET, it is
generally assumed that these CAs will be mutually
recognized.
4. Proposed System
In this paper achieving location privacy in VNs with
randomly changing identifiers in the presence of a global
passive adversary. We are fully aware of the need for strong
security in VNs, along with privacy protection. In particular,
in this context, pseudonyms are anonymized public keys.
Our proposal fits in this framework of pseudonymous
authentication. Our contribution is threefold. First, we
propose a protocol to create cryptographic mix-zones at road
inter sections. This solution thwarts computationally
bounded eavesdroppers while preserving the functionality of
safety messages. Second, we analyze the location privacy
achieved by combining mix-zones into mix-networks in
VNs. These so-called vehicular mix-networks leverage on
the mobility of vehicles and the dynamics of road
intersections to mix vehicle identifiers. Finally, we show by
means of simulations the effectiveness of the proposed mix
system.
4.1 Network Model
Vehicular Networks (VNs) consist of vehicles, Road-Side
Units (RSUs) and a collection of backbone servers
accessible via the RSUs. We assume that a single VN
Operator (VNO) is responsible for deploying RSUs in the
network. Due to their relevance to life-critical applications,
VNs have to satisfy several strict requirements, namely
sender and data authenticity, availability, liability, and real-
time delivery. VNs are a very challenging application of ad-
hoc networks as all the above prerequisites must be achieved
under the stringent conditions created by a highly dynamic
mobile environment. To prevent accidents and inform each
other of dangerous situations, vehicles periodically
broadcast safety messages indicating their position, speed,
acceleration, and possibly many other types of information
(Fig. 1). We assume that each vehicle is equipped with a
GPS device that provides accurate location information
within an acceptable error margin.
Similarly to the work in, we assume that a suitable public
key infrastructure is available in VNs and that the messages
are properly signed to ensure the liability of their sender in
case of an accident. A certificate is attached to each message
to enable other vehicles to verify the sender's authenticity.
Vehicles are equipped with Tamper-Proof Devices (TPDs)
that guarantee the correct execution of cryptographic
operations and the non-disclosure of private keying material.
4.2 Cryptographic Mix-Zones
A mix-zone is an anonymizing region that obfuscates the
relation between entering and exiting vehicles. The
adversary observes the timing and the location of the
entering and exiting vehicles in order to derive a probability
distribution over the possible mappings. In VNs, because we
assume that mix-zones are located at road intersections, the
timing of events depends on the delay characteristics of the
intersection structure. Likewise, the location of entering and
exiting vehicles depends on their trajectory in an
intersection. Since the location of mix-zones is fixed, the
adversary can identify them and thus could easily attempt to
eavesdrop transmissions originating in the mix-zone area. To
solve this problem, we introduce the CMIX Protocol to
create Cryptographic MIX-zones: all legitimate vehicles
within the mix-zone obtain a symmetric key from the road-
side unit (RSU) of the mix-zone, and utilize this key to
encrypt all their messages while within the zone. The
symmetric key is obtained through a key establishment
phase. To ensure the functionality of safety messages, this
mix-zone key can be obtained by nodes approaching the
mix-zone with the help of a key forwarding mechanism, and,
finally, the RSU can swap to a new key through a key
update mechanism. AES Symmetric Key Encryption
provides data confidentiality.
Hash Code of Message encrypted with sender’s Private Key
providing a digital signature. (Since only the sender could
have produced the encrypted hash code). Even if the attacker
came to know of the symmetric key, in order to alter the
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message and get away with it, he would have to know the
sender’s private key.
4.2.1 Key Establishment
Symmetric Key systems were the first type of cryptosystems
used to secure information. In these systems, nodes can only
communicate after sharing and agreeing on a secret key that
is used to process communication messages. As stated
previously, VANETs are a relatively new research area and
the security for such networks is only starting to be a major
research topic. Hence, there are not many papers that
propose the use of such systems for VANET security as the
attention is more directed towards Public Key and Identity
Based systems. Nevertheless, this section discusses existing
proposals of using Symmetric Key systems for VANET
security.
The Key Establishment protocol. Ts is a time stamp, Sign ()
is the signature of the message, Cert is the certificate of the
message sender. As soon as a vehicle vi enters in the of
transmission range of an RSU, R Beacon, it initiates the key
establishment protocol described. As the vehicle knows its
own location and the location of the RSU (announced in the
beacon), it can estimate whether it is within the mix-zone,
defined by a transmission range RCMIX < R Beacon. If so,
the vehicle vi broadcasts one or, if needed, several key
request messages (first message in Table 1). The RSU
replies with the symmetric key SK encrypted with the public
key of vehicle vi and a signature. vi receives and decrypts
the message. If the message is validated, vi acknowledges it
and SK can be used to encrypt all subsequent safety
messages until vi leaves the mix-zone. In case RSUs are co-
located (i.e., their mix-zones overlap), vehicles are aware of
all CMIX keys so that they can decrypt all messages.
Alternatively, co-located RSUs could coordinate to use the
same CMIX key.
4.2.2 Key Forwarding
Vehicles in the extended mix-zone, that is, at a distance d
from the RSU where RCMIX < d < R Beacon may be
unable to obtain directly the key from the RSU; for example,
they are beyond their transceiver's range for bidirectional
communication. Thus, they cannot decrypt safety messages
coming out of the CMIX. As vehicles know they are within
an RSU transmission range, when they receive encrypted
safety messages, they issue one or, if needed, several key
requests to obtain the SK key with the help of vehicles
already in the mix-zone which are aware of it.
The signature from the RSU, along with the time stamp,
allows validating the transmitted symmetric key. Note that
vehicles in the extended region do not encrypt their safety
messages with the CMIX key before entering the mix-zone
(RCMIX). The entire above message is in addition signed by
v1.
4.2.3 Key Update
Propose a Key Update mechanism to renew or revoke CMIX
symmetric keys. The RSU is responsible for such key
updates and determines when to initiate the process. Key
updates occur only when the mix-zone is empty and vehicles
obtain new keys via the key transport and key forward
protocols. The CA obtains the new symmetric key from the
RSU over a secure channel, to satisfy the liability
requirements (i.e., possibly, decrypt safety messages in the
future). The robustness provided by the system is increased,
if key up dates are asynchronous across different base
stations. But there is a trade of between security and cost, as
frequent updates can incur additional overhead.
5. Simulation Results
Presents the average location privacy obtained in an
intersection for various vehicle densities. We show that the
achieved location privacy varies with respect to the traffic
congestion and the vehicle density. We observe that the less
congested the traffic is, and the easier it is for the adversary
to track vehicles based on their delay characteristics. The
upper bound is the average of over the number of user per
intersection in the simulation.
Table 1: Table showing the Simulation parameters
Parameter Value
Field Size 3000X3000m
MAC 802.11
Fading Rayleigh
Simulation Time 60s or user define
Number of (s,d) paris 10
Number of nodes 25…100
Presents the success probability of an adversary in tracking
vehicles. The adversary success probability is the ratio of the
number of successfully mapped vehicles to the total number
of vehicles in a mix-zone, averaged over all mix-zones. As
expected, the success ratio decreases as the entropy
increases. Even with a high ½ and congested traffic, the
adversary success ratio is relatively high. We show next that
the combination of mix-zones into mix-networks
significantly reduces this success ratio.
Table 2: Comparison of node disjoint path
Number of Nodes 0 100 200 300 400 500 600 700
Geocast(AAG) 2 2 2 2 2 2 2 2
Aggregation 2 4 6 8.3 10 12 11 10.8
Baseline 4 12 21 32 44.6 50 55 60
Proposed 1.2 1.5 1.53 1.65 1.67 1.87 1.9 1.99
Figure 2: Number of node v/s node disjoint path
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In figure 2 check with different type exiting system method
with proposed one here we show to reduce the disjoint path
in proposed system.
Table 3: Comparison of information routing
Distribution of information 0 20 40 60 80 100
Existing City 100 nodes 5 21 22 22.65 23 28
Proposed City 100 nodes 5.4 22.4 24 28 30 35.4
Existing Highway 50 nodes 21 40 40 41 43 46
Proposed 50 nodes 23 45 46.4 48 56 70
Figure 3: Information with different topology
Figure 3, information distribution compare with existing
method with new method.
6. Conclusion
The problem of providing location privacy in vehicular
networks. Introduce the zone based security protocol to
create AES algorithm and cryptographic mix-zones at road
intersections wherein vehicles can change their pseudonyms.
Vehicular mix-networks rely on the mobility of vehicles to
provide location privacy the efficiency of safety messages.
Further, we proposed an anonymous access protocol to
address threats to privacy that arise due to access to LBS
(location based service) applications, and found that it was
robust under the global adversary model, as well as under
the safety application constraints. Future work includes
evaluation of proposed location privacy solutions under
more realistic mobility for vehicles, combined with map
data, and with communication traffic models.
References
[1] R. Beresford. Location privacy in ubiquitous
computing. Technical Report 612, University of
Cambridge, January 2005.
[2] R. Beresford and F. Stajano. Mix-zones: User privacy in
location-aware services. In Proceedings of PerSec,
2004.
[3] L. Butty an, T. Holczer, and I. Vajda. On the
effectiveness of changing pseudonyms to provide
location privacy in VANETs. In Proceedings of ESAS,
2007.
[4] G. Calandriello, P. Papadimitratos, A. Lloy, and J.P.
Hubaux. Efficient and robust pseudonymous
authentication in vanets. In The Fourth ACM
International Workshop on Vehicular Ad Hoc Networks
(VANET), 2007.
[5] D. Chaum. Untraceable electronic mail, return
addresses, and digital pseudonyms. Communications of
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[6] M. Gerlach and F. GÄuttler. Privacy in VANETs using
changing pseudonyms - ideal and real. In Proceedings
of VTC, April 2007.
[7] M. Gruteser and D. Grunwald. Enhancing location
privacy in wireless LAN through disposable interface
identiffers: a quantitative analysis. Mobile Networksand
Applications, 10(3):315-325, June 2005.
[8] Hoh and M. Gruteser. Protecting location privacy
through path confusion. In Proceedings of
SECURECOMM, pages 194-205, 2005.
[9] L. Huang, K. Matsuura, H. Yamane, and K. Sezaki.
Towards modelling wireless location privacy. In
Proceedings of PET, 2005.
[10]L. Huang, K. Matsuura, H. Yamane, and K. Sezaki.
Silent cascade: Enhancing location privacy without
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Author Profile
S. Kavitha M.Sc (C.S), Pursuing M. Phil (CS) in Sri
Jayendra Saraswathy Maha Vidyalaya CAS, Area of
Interest, Networking, Software Project management.,
M. Parveentaj M.C.A., ADCA, M.Phil., working as
an Associate Professor, in Department of Computer
Science- Sri Jayendra Saraswathy Maha Vidyalaya
CAS for a passed 8years. Area of Interested;
Networking, Data Mining, Software Engineering.
Presented 2 papers in an International Conference, 1 paper in
National Level.
Paper ID: 12013148 118

Security in Vehicular Ad Hoc Networks through Mix-Zones Based Privacy

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