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Abstract
Vehicular Ad Hoc Networks (VANET) is a unique platform to improve road safety and increase passenger convenience in vehicles. In the existing system, they use the air as a medium for communication; they are out in the open to several suspicions in the network that influences the reliability of these features. The need for a robust VANET networks is strongly dependent on their security and time alone features through routing, which will be conferred in this paper. In this paper a various types of routing and security problems of VANET been analyzed and discussed; we also discuss a set of way out presentation to solve these challenges and problems.
I. INTRODUCTION
Vehicular ad hoc network is a special form of MANET which is a vehicle to vehicle & vehicle roadside wireless communication network. It is autonomous & self-organizing wireless communication network, where nodes in VANET involve themselves as servers and/or clients for exchanging & sharing information [3]. With a sharp increase of vehicles on the road, new technology is envisioned to provide facilities to the passengers including safety application, assistance to the drivers, emergency warning etc.
Vehicular Ad-Hoc Networks (VANETs) is an application of MANETs that allows for communication between road transports vehicles and promotes safety on roads. There is however situations that could cause harm to the vehicle and/or its occupants; vehicles could be tracked,
Followed or have their messages monitored. Vehicular ad hoc network (VANET) is a sub class of MANET with some unique properties. VANETs have emerging out these days due to the need for supporting the increased number of wireless equipments that can be used in vehicles [1]. Some of these products are global positioning system, mobile phones and laptops. VANETs have some dissimilar properties then MANETs like road pattern restrictions, no restriction on network size, dynamic topology, mobility models, and infinite energy supply, localization functionality and so on. All these characteristics made VANET environment a challenging for developing efficient routing protocols. The major factor in it is the rapidly moving mobile nodes.
The increasing mobility of people has caused a high cost for societies as consequence of the increasing number of traffic congestion, fatalities and injuries. Vehicular Ad-Hoc Networks (VANETs) envisage supporting services on Intelligent Transportation Systems (ITSs), as collective monitoring of traffic, collision avoidance, vehicle navigation, control of traffic lights, and traffic congestion management by signaling to drivers. VANETs comprise vehicles and roadside equipments owning wireless interfaces able to communicate among them by wireless and multi-hop communication. VANET security should satisfy four goals [5], it should ensure that the information received correct (information authenticity), the source is who he claims to be (message integrity and source authentication), the node sending the message cannot be identified and tracked (privacy) and the system is robust.
In the year 1998, the team of engineers from Delphi Delco Electronics System and IBM Corporation proposed a network vehicle concept aimed at providing a wide range of applications [1]. With the advancements in wireless communications technology, the concept of network car has attracted the
Attention all over the world. In recent years, many new projects have been launched, targeting on realizing the dream of networking car and successful implementation of vehicular networks. The project Network on Wheels (NOW) [1] is a German research project founded by DaimlerChrysler AG, BMW AG, Volkswagen AG, Fraunhofer Institute for Open Communication Systems, NEC Deutschland GmbH and Siemens AG in 2004, the project adopts an IEEE 802.11 standard for wireless access. The main objectives of this project are to solve technical issues related to communication protocols and data security for car -to-car communications. The Car2Car Communication Consortium [16] is initiated by six European car manufacturers. Its goal is to create a European industrial standard for car-to-car communications extend across all brands. FleetNet [1]
was another European program which ran from 2000 to 2003 this ad hoc research was dominated by efforts to standardize MANET protocols, and this MANET research focused on the network layer[1], the ultimate challenge was to solve the problem of how to reach nodes not directly within radio range
by employing neighbors as forwarders, while the European Commission is pushing for a new research effort in this area in order to reach the goal of reducing the car accidents of 50% by 2010, aiming to reach a satisfactory level of secure VANET. CarTALK 2000 is a European Project focusing on new driver assistance systems which are based upon inter -vehicle communication. The main objectives are the development of cooperative driver assistance systems on the one hand and the development of a self-organizing ad-hoc radio network as a communication basis with the aim of preparing a future standard. As for the assistance system, the main issues are: a) assessment of today's and future applications for co-operative driver assistance systems, b) development of software structures and algorithms, i.e. New fusion techniques, c) testing and demonstrating assistance functions in probe vehicles in real or reconstructed traffic scenarios. To achieve a suitable communication system, algorithms for radio ad-hoc networks with extremely high dynamic network topologies are developed and prototypes tested in the vehicles. Apart from technological goals, CarTALK 2000 actively addresses market introduction strategies including cost/benefit analyses and legal aspects, and aims at the standardization to bring these systems to the European market. CarTALK 2000 started in August 2001 as a three-year project which is funded within the IST Cluster
of the 5th Framework Program of the European Commission.
a. VANET Structure
A VANET turns every participating car into a wireless router or node, allowing cars approximately 100 to 300 meters of each other to connect and, in turn, create a network with a wide range. As cars fall out of the signal range and drop out of the network, other cars can join in, connecting vehicles to one another so that a mobile Internet is created. Vehicular communication systems are a type of network in which vehicles and roadside units are the communicating nodes, providing each other with information, such as safety warnings and traffic information. As a cooperative approach, vehicular communication systems can be more effective in avoiding accidents and traffic congestions than if each vehicle tries to solve these problems individually. Generally, vehicular networks are considered to contain two types of nodes: vehicles and roadside stations as shown in figure 1. The network should support both private data communications and public (mainly safety) communications but higher priority is given to public communications. There are three primary components of the VANET [4]: Onboard unit (OBU), Roadside unit (RSU) and the backhaul network.
b. VANET Working
Vehicular Networks System consists of large number of nodes, approximately number of vehicles exceeding 750 million in the world today [4], these vehicles will require an authority to govern it, each vehicle can communicate with other vehicles using short radio signals DSRC (5.9 GHz), for range can reach 1 KM, this communication is an Ad Hoc communication that means each connected node can move freely, no wires required, the routers used called Road Side Unit (RSU), the RSU works as a router between the vehicles on the road and connected to other network devices.
VANET CHARACTERISTICS
The characteristics of a vehicular ad hoc network are unique compared to other mobile ad hoc networks. The distinguishing properties of a VANET offer opportunities to increase network performance, and at the same time it presents considerable challenges. A VANET is fundamentally different [5] from other MANETs.
High Mobility:
The nodes in VANETs usually are moving at high speed. This makes harder to predict a node’s position and making protection of node privacy [2].
Rapidly changing network topology:
Due to high node mobility and random speed of vehicles, the position of node changes frequently. As a result of this, network topology in VANETs tends to change frequently [3].
Unbounded network size:
VANET can be implemented for one city, several cities or for countries. This means that network size in VANET is geographically unbounded [3].
Frequent exchange of information:
The ad hoc nature of VANET motivates the nodes to gather information from the other vehicles and road side units. Hence the information exchange among node becomes frequent.
Wireless Communication:
VANET is designed for the wireless environment. Nodes are connected and exchange their information via wireless. Therefore some security measure must be considered in communication [2].
Time Critical:
The information in VANET must be delivered to the nodes with in time limit so that a decision can be made by the node and perform action accordingly.
Sufficient Energy:
The VANET nodes have no issue of energy and computation resources. This allows VANET usage of demanding techniques such as RSA, ECDSA implementation and also provides unlimited transmission power [2].\
III. APPLICATIONS
Major applications of VANET embody providing safety data, traffic management, toll services, location primarily based services and documentary. One among the foremost applications of VANET embody providing safety connected data to avoid collisions, reducing compile of vehicles when associate accident and providing warnings associated with state of roads and intersections. Mounted with the security connected data are the liability connected messages, which might confirm that vehicles are present at the location of the accident and later facilitate in fixing responsibility for the accident.
a. Intelligent transportation applications
Intelligent transport system(ITS) that embody a range of applications like on global positioning system, traffic observation, analysis of traffic jam, management of traffic system, and diversion of routes which support the traffic scenario. As an example, existing roadside unit observing traffic on the roads and send all the information to a central authority that analyze them to control traffic flow so that the best traffic signal schedules will be designed.
b. Comfort applications
Those applications which permit the clients to share information either with alternative clients in vehicles or with others having anywhere on the web to improve comfort of clients are known as comfort applications. For instance, VANETs allows vehicular nodes to connect with web to so that
the back seat passengers will play games or transfer music. Usually, some dynamic or fastened allotted networks to internet gateways are summed up with the networks, so that it will send the data packets to the VANETs and therefore the web [ 1].
c. Collision Avoidance
Vehicles to vehicles and vehicles to roadside unit communications will save several lives and forestall injuries. According to this application, if a vehicle reduces its speed considerably once identifying an accident then vehicle broadcast its location to its neighbor vehicles [1]. And different receivers can try to transfer the message to the vehicles further behind them and therefore the vehicle in question can emit some alarm to its vehicles and different vehicles behind. During this process, a lot of vehicles way behind can get an alarm signal before they see the accident and may take any better decision.
d. Cooperative Driving
The drivers play a major role during this application. Like turn conflict warning, violation warning, curve warning, lane merging warning etc. These services might nobly lower the life-endangering accidents. In fact, several of the accidents come back from the dearth of cooperation between drivers.
Given a lot of information concerning the doable conflicts, we will stop several accidents [1].
e. Payment Services
This application is incredibly appropriate for toll assortment while not even decelerating the vehicle or waiting in line.
f. Location-based Services
Finding the nearest fuel station, motels, cafes etc. is done effectively by exploitation of location based service. GPS system is used to elaborate these kinds of services in VANET. The various applications of VANETs are [5] to assist the driver, data dissemination, parking problems, emergency vehicle warning, maintenance of minimum security distance, internet connectivity, peer to peer application, congestion on the road, information about intersections, and many more.
IV. CHALLENGES IN VANET
The security of VANET has mostly directed the attention of today research efforts, while comprehensive solutions to protect the network from adversary and attacks still need to be improved, trying to reach a satisfactory level, for the driver and manufacturer to achieve safety of life and infotainment.
4.1 Vehicular Security Challenges
VANET face many security attacks and these attacks and threat can be categorized in few classes.
The five different types of classes for the attacks with the aim to provide an easy identification with association to respective class. Each of the classes will represent different types of attack level and priority. Below are the proposed classes of attack:
a. Network Attack:
Network attacks are always on the top of the list and are classified as a top priority since it can be dangerous to the entire network. A single successful network attack may easily affect the whole network. Few example of network attack are such as Denial of service (DOS) Attack and Sybil Attack.
Denial of Service attack:
As shown in figure 3 this attack happens when the attacker takes control of a vehicle’s resources or jams the communication channel used by the Vehicular Network, so it prevents critical information from arriving. It also increases the danger to the driver, if it has to depend on the application’s information.
Sybil Attack:
This attack happens when an attacker creates large number of pseudonymous, and claims or acts like it is more than a hundred vehicles, to tell other vehicles that there is jam ahead, and force them to take alternate route[3][4]. Sybil attack depends on how cheaply identities can be generated as shown
in figure 4. For instance an attacker can pretend and act like a hundred vehicle to convince the other vehicles in the road that there is congestion, go to another rout, so the road will be clear.
b. Application Attack:
In application attack class, the attacker attention is no other than to manipulate application content for its own benefit. These attackers will tend to suppress or alter the actual message and change it with a false content which may cause harm to other vehicle. This type of attack might be done by
either malicious or rational attacker for fun or to serve their own benefits. Few examples of application attack are such as message suppression attack, fabrication attack, alteration attack
Fabrication Attack:
An attacker can make this attack by transmitting f alse information into the network, the information could be false or the transmitter could claim that it is somebody else as shown in figure 5. This attack includes fabricate messages, warnings, certificates, identities
Alteration Attack:
This attack happens when attacker alters an existing data, it includes delaying the transmission of the information, replaying earlier transmission, or altering the actual entry of the data transmitted [3]. For instance, as shown in figure 6 ban attacker can alter a message telling other vehicles that the current road is clear while the road is congested [5].
c. Social Attack:
Social attack contains all unmoral and emotional messages [4]. The main objective in most of social attack is to indirectly create problem in the network by bad and unwanted messages which can affect the behavior of others road users.
Tunnel Attack:
Since GPS signals disappear in tunnels, an attacker may exploit this temporary loss of positioning information to inject false data once the vehicle leaves the tunnel and before it receives an authentic position update as shown in figure 7. The physical tunnel in this example can also be replaced by an area jammed by the attacker, which results in the same effects.
Monitoring Attack:
Monitoring attack is a serious threat for the road safety officials. In this kind of attack, the attackers which can be considered both local and outsider would silently monitor and track important messages which are not supposed to be release in public network. Attackers would use the valuable information gathered from eavesdropping to serve their own benefit. In monitoring attack, the attacker just monitor the whole network, listen the communication between V2V and V2I. If they find any related information then pass this information to concern person.
Eavesdropping:
Eavesdropping is a network layer attack consisting of capturing packets from the network transmitted by others' computers and reading the data content in search of sensitive information like passwords, session tokens, or any kind of confidential information.
Eavesdropping is secretly listening to the private conversation of others without their consent as shown in figure 8. Eavesdropping is the unauthorized real-time interception of a private communication, such as a phone call, instant message, video conference or fax transmission. The term eavesdrop derives from the practice of actually standing under the eaves of a house, listening to conversations inside Eavesdropping can also be done over telephone lines (wiretapping), email, instant messaging, and other methods of communication considered private.
4.2 Vehicular Networks Challenges
Mobility
The basic idea from Ad Hoc Networks is that each node in the network is mobile, and can move from one place to another within the coverage area, but still the mobility is limited, in Vehicular Ad Hoc Networks nodes moving in high mobility, vehicles make connection throw their way with another vehicles that maybe never faced before, and this connection lasts for only few seconds as each vehicle goes in its direction, and these two vehicles may never meet again. So securing mobility challenge is hard problem [3].
Volatility
The connectivity among nodes can be highly ephemeral, and maybe will not happen again, vehicles travelling throw coverage area and making connection with other vehicles, these connections will be lost as each car has a high mobility, and maybe will travel in opposite direction[1][3]. Vehicular networks lacks the relatively long life context, so personal contact of user’s device to a hot spot will require long life password and this will be impractical for securing VC [5].
Privacy VS Authentication
The importance of authentication in Vehicular Ad Hoc Networks is to prevent Sybil Attack that been discussed earlier [3]. To avoid this problem we can give a specific identity for every vehicle, but this solution will not be appropriate for the most of the drivers who wish to keep their information protected and private[1][3].
Privacy VS Liability
Liability will give a good opportunity for legal investigation and this data can’t be denied (in case of accidents)[1], in other hand the privacy mustn’t be violated and each driver must have the ability to keep his personal information from others (Identity, Driving Path, Account Number f or toll Collector etc.) [5].
Network Scalability
The scale of this network in the world approximately exceeding the 750 million nodes [5], and this number is growing, another problem arise when we must know that there is no a global authority govern the standards for this network [5], for example: the standards for DSRC in North America is deferent from the DSRC standards in Europe, the standards for the GM Vehicles is deferent from the BMW one.
Bootstrap
At this moment only few number of cars will be have the equipment required for the DSRC radios, so if we make a communication we have to assume that there is a limited number of cars that will receive the communication, in the future we must concentrate on getting the number higher, to get a financial benefit that will courage the commercial firms to invest in this technology [5].
4.3 Vehicular Technical Challenges
The technical challenges deals with the technical obstacles which should be resolved before the deployment of VANET. Some challenges are given below:
Network Management:
Due to high mobility, the network topology and channel condition change rapidly. Due to this, we can’t use structures like tree because these structures can’t be set up and maintained as rapidly as the topology changed [2].
Congestion and collision Control:
The unbounded network size also creates a challenge. The traffic load is low in rural areas and night in even urban areas. Due to this, the network partitions frequently occurs while in rush hours the traffic load is very high and hence network is congested and collision occurs in the network.
Environmental Impact:
VANETs use the electromagnetic waves for communication. These waves are affected by the environment. Hence to deploy the VANET the environmental impact must be considered.
MAC Design:
VANET generally use the shared medium to communicate hence the MAC design is the key issue. Many approaches have been given like TDMA, SDMA, and CSMA etc. IEEE 802.11 adopted the CSMA based Mac for VANET.
Security:
As VANET provides the road safety applications which are life critical therefore security of these messages must be satisfied.
V. CURRENT SOLUTIONS
There are many solutions provided to mitigate the attacks in VANET. The following are the five most effective solutions that are most commonly used. The system should be able to help establish the liability of drivers; but at the same time, it should protect the privacy of the drivers and passengers [2].
B. Dahilletal proposed a secure routing protocol for ad hoc network based on authentication. This is based on AODV but it prevents from attacks including spoofing. ARAN uses the public key cryptography and requires a certificate server whose public key is known to all nodes. It uses timestamp for the freshness of the route. A source node broadcasts the route discovery packet (RDP) to all its neighbors for route discovery [2]. Each node keeps the record of its neighbor from which it receives the message. After receiving the message all the neighbor again forwards this message to their neighbors with their sign and own certificate. When the message received by the destination, it replies to the first node from which it received the message. No intermediate node can reply the RDP other than destination even if that intermediate node knows the path of destination. The destinations will unicast the reply (REP) in reverse from destination to source. All REP is signed by the sender and checked by the next hop. For the shortest path, the source begins with the encrypted shortest path confirmation (SPC) message and broadcasts it to its neighbor. Destination node replies with the recorded shortest path (RSP) to the source through its predecessor. Each neighbor signs the encrypted part of the message and attaches its certificate. ARAN requires that each node must keep one routing table for each node in a network. When no traffic is found on node in lifetime it is simply deactivated from the table. If data is received on inactive route, the error message ERR is generated which travels through reverse path of the source.
If a node is broken due to the node movement, the ERR message is generated.
5.2. SEAD (Secure and Efficient Ad hoc Distance Vector):
Y. C. Hu, D. B. Johnson and A. Perrig proposed a new secure routing protocol which protects against multiple uncoordinated attackers who creates incorrect routing in any other node. It is based on the Destination sequenced Distance Vector (DSDV) routing. SEAD supports the node which has limited CPU processing capability and protects from the DoS attack in which attackers attempts to consume excess network bandwidth. It uses the one way hash function rather than more expensive asymmetric cryptographic operation. ++One way hash function is created by choosing a random initial vale through the node
CONCLUSION
Security is the major issue to implement the VANET. The study of attacks revealed that the attacker generally targets the network layer directly or indirectly hence the routing protocol must be secure enough to prevent the most types of attacks. Each solution must preserve the security requirements
like authentication, integrity, and privacy which are more targeted. Vehicular Ad Hoc Networks is an emerging and promising technology, this technology is a fertile region for attackers, who will try to challenge the network with their malicious attacks. This report gives a wide analysis for the current challenges and solutions. Apart from ensuring availability of information that provides a safer driving behavior and a better travelling experience, the network is an economic, communication, and knowledge management enabler. However, despite the benefits, information security threats and privacy issues pose an enormous challenge to VANET expansion and usage. One of the most interesting parts of the network is the ability of the network to self- organize in a highly mobile network environment. This paper provided readers with a succinct anecdote of the network by describing the network characteristics, architecture, applications, communication patterns, and security challenges.