Security and Privacy issues of Mobile Ad-Hoc NetworksIntroduction:
This assignment based upon security and privacy issues of mobile ad-hoc nettwork.
Background
Ad hoc networks are a new standard of wireless communication for movable hosts (which is called nodes). In an ad hoc network, there is no fixed infrastructure such as base stations or mobile switching centres. Mobile nodes that are within each other’s radio range communicate directly via wireless links, while those that are far apart rely on other nodes to relay messages as routers. Node mobility in an ad hoc network causes frequent changes of the network topology [1]. Figure 1.1 shows such an example: initially, nodes A and D have a direct link between them. When D moves out of A’s radio range, the link is broken. However, the network is still connected, because A can reach D through C, E, and F.
Nodes A, B, C, D, E, and F constitute an ad hoc network. The circle represents the radio range of node A. The network initially has the topology in (a). Node D moves out of the radio range of A, the network topology changes to the one in (b).
Challenges against Ad-hoc Networks
The salient features of Ad hoc networks pose both challenges and opportunities in achieving these security goals.
First, use of wireless links renders an ad hoc network susceptible to link attacks ranging from passive eavesdropping to active impersonation, message reply, and message distortion. Eavesdropping might give an adversary access to secret information, violating confidentiality. Active attacks might allow the adversary to delete message, to inject erroneous message, to modify message, and to impersonate a node, thus violating availability, integrity, authentication, and non-repudiation.
Secondly, node, roaming in a hostile environment with relatively poor physical protection, has non-negligible probability of being compromised. Therefore, we should not only consider malicious attacks from outside a network, but also take into account the attacks launched from within the network by compromised nodes. Therefore, to achieve high survivability, ad hoc networks should have a distributed architecture with no central entities. Introducing any central entity into our security solution could lead to significant vulnerability, that is, if this centralized entity is compromised, then the entire network is subverted.
Thirdly an ad hoc network is dynamic because of frequent changes in both its topology and its membership. Trust relationship among nodes also changes, for example, when certain nodes are detected as being compromised. Unlike other wireless mobile networks, such as mobile IP, nodes in an ad hoc network may dynamically become affiliated with administrative domains. Any security solution with a static configuration would not suffice. It is desirable for our security mechanisms to adapt on the fly to these changes [6].
Finally, ad hoc network may consist of hundreds or even thousands of nodes. Security mechanisms should be scalable to handle such a large network.
Properties of Ad Hoc Networks
Wireless mobile ad hoc networks have significant properties which are as follows:
Dynamic Network Topology
Each node in ad hoc network is free to move randomly. This feature makes the network topology change unpredictable. Also an ad hoc network may be comprised of both bi-directional and unidirectional links [3]. Thus using ad hoc networks could augment mobility and flexibility of nodes in the network [3]. Even though the network topology varies, connectivity in the network should be maintained to allow applications and services to operate without disruption. In particular, this characteristic will affect the design of routing protocols. In addition, a user in an ad hoc network will require access to a fixed network, such as the Internet, even if nodes are mobile. This needs mobility management functions allowing network access for devices located several radio hops away from a network access point [3]
Bandwidth-limited and Fluctuating Capacity Link
Wireless links will remain to have substantially lower capacity compared to their hardwired counterpart [03]. Beside the throughput of wireless communication in real environments is often much less than a radios maximum transmission rate, because there may be the effects of multiple accesses, fading, noise, and interference condition and so on.
The effects of high bit error rates may be more severe in a multi-hop Ad hoc network, because the aggregate of all link errors affects a multi-hop path. Moreover, more then one end-to-end route can use a given link if the link were to break. This could disrupt several sessions. However, efficient function for link layer protection, such as forward error correction (FEC) and automatic repeat request (ARQ), can significantly improve the link quality [3].
Low –power and Resource Limited Operation
In most cases, the network nodes in a wireless Ad hoc network may depend on batteries or other exhaustible means for their energy [3]. This feature makes the power budget tight for all the power-consuming components in a mobile device. For example, this will after CPU processing, memory size and usage, signal processing, and transceiver output/input power [3]. For these nodes, energy conservation should be consider for the optimization as a key system design criterion [3]
Constrained Physical Security
In general, mobile wireless networks more likely to be vulnerable to physical security threats than are fixed-cable nets. For example, there is the increased possibility of eavesdropping, spoofing, and denial of service attack that should be carefully considered. Often current link security techniques are applied to wireless networks security threats [3].
Decentralized Network Control
As an advantage, the decentralized nature of network control in mobile Ad hoc networks supports extra robustness against the single points of failure of more centralized approaches [3].
Complexity of Ad Hoc networking
Despite the fact that the management of the physical layer is of fundamental importance, there has been very little research in this area; node in mobile Ad hoc networks are confronted with a number problems, which in existing mobile networks are solved by base stations. The solution space range from hierarchical cell structures is completely Ad hoc stochastic allocations. Power management is of paramount importance. General strategies for saving power need to be addressed, as well as adoptions to the specifics of nodes of general channel and source coding methods, ratio resource management and multiple accesses.
Mobile Ad hoc networks do not rely on one single technology, instead they should be able to capitalize on technology advances. One challenge is to define a set of abstractions that can be used by the upper layers and still not preclude the use of new physical layer methods as they emerge. Primitives of such abstraction are, for example the capabilities and covering ranges of multicast and nicest channel. Information such as node distribution, network density, link failures etc, must be shared among layers and the MAC layer and the network layer need to collaboration order to have a better view of network topology and to optimize the number of message in the network.
Mobile ad hoc networking has the unique characteristics of being totally independent from any authority of infrastructure, providing great potential for the users. In fact roughly speaking, two or more users become ad hoc network simple by being close enough to radio constrains, without any external intervention. Moreover, telecommunication networks are expected to grow with the advent new application. Although in the past telecommunication networks were suited and developed as separate building blocks, for users of mobile ad hoc networks interaction between higher layers and low layers is essential. The network can be highly dynamic, implying that traditional routing algorithms will either not stabilize or will generate many routing updates and rapid response to topology change is needed [36].
Objective
In ad hoc network, providing security is a challenging task. Because, wireless medium is lack of central control and dynamic topology. Our objective in this thesis is to provide a group member authentication protocol, which can improve the security of ad hoc network. When new node comes to connect in network then the new node needs to maintain some procedure for becoming a new member of the network. For that reason in this thesis, some verification process has been designed and implemented for a new node. After this verification, a new node is allowed to become a new member in the network. To ensure the group member authentication in secure way our objective is to design and implement the protocol which is known as Zero Knowledge Proof and Threshold Cryptography. This will ensure the authentication of a new member node in the network.
Methodology
In our thesis it has been implemented group member authentication protocol. For improving security by group member authentication protocol it has been implemented threshold cryptography, zero knowledge proof and broadcast message send request to member of the network, which is known as Shareholder through multicast channel. The overview methodologies of our group authentication protocol are described below:
Distributor who gives secret to the members acts as a networks administrator for ad hoc network. It distributes share key to every member of this ad hoc network. After completing the distributions of share key to the share holders of the network when network is established, distributor doesn’t exist in this network. Shareholder stores there own key and listens for new node to join this network. New nodes, which want to join in the network, send a joining request through multicast channel. Multicast channel broadcast this request to all the member of this network. Shareholders send their acknowledgment to requested node that “I am share holder, this is my address”. Address is basically an IP, port no. When new node gets acknowledgement from shareholders then it select‘t’ number of shareholders. ‘t ‘ is a threshold value of this ad hoc network. New node establish a zero knowledge proof session for‘t’ number of share holders simultaneously. Zero knowledge proof session ensure the authentication of a node of that network. After getting ‘t’ number of shared key from share holder’s new node can generate the secret key. Secret key is essential key to becoming a member of this ad hoc network.
Outline of Research
In this section is mentioned chapter wise over all outline of our research methodology.
Chapter 2 is related works where mentioned basic concepts of ad hoc networks, types of ad hoc networks, features and application of ad hoc networks, and finally also mentioned some advantages and disadvantages of ad hoc networks.
Chapter 3 is security issues where discussed about the security requirements of mobile ad hoc networks, vulnerabilities, various types of attacks and threats of mobile ad hoc networks, and some problems to provide security to mobile ad hoc networks.
Chapter 4 is security in routing protocol of ad hoc networks which described some well known ad hoc routing protocols that is necessary to make the routing decision and also their existing problems.
Chapter 5 is proposed group authentication protocol where depicted some idea to a new proposed protocol which is the security part of the Ad hoc network and will be able to improve the security of the ad hoc network. And finally the Chapter 6 is our conclusion part where we gave some opinion and also shared our idea for future.
Summary
In this chapter, ad hoc network background, security emergence, our objective, methodology and also outline of this thesis project are discussed. In an ad hoc network, there is no fixed infrastructure such as base stations or mobile switching canters. Mobile nodes that are within each other’s radio range communicate directly via wireless links, while those that are far apart rely on other nodes to relay messages as routers. Node mobility in an ad hoc network causes frequent changes of the network topology.
Security is an important issue for ad hoc networks, especially for the security-sensitive applications. To secure an ad hoc network, it has been considered the following attributes: availability, confidentiality, integrity, authentication, and non-repudiation. Achieving security within ad hoc networking is challenging due to some reasons are eavesdropping in channel, vulnerability of nodes, absence of infrastructure, changing topology dynamically, man in middle attack etc.
Related Work
Ad hoc networks consist of mobile nodes interconnected by wireless multi-hop communication paths. Unlike conventional wireless networks, ad hoc networks have no fixed network infrastructure or administrative support. The topology of such networks changes dynamically as mobile nodes join or depart the network or radio links between nodes become unusable. Supporting appropriate quality of service for mobile ad hoc network is a complex and difficult task because of the dynamic nature of the network topology. This chapter presents the basic concepts of ah hoc network, features of ah hoc network, types of ah hoc network, application and, advantages and disadvantages of ad hoc network.
Introduction
An ad-hoc or short-live network is the network of two or more mobile devices connected to each other without the help of intervening infrastructure. In contrast to a fixed wireless network, an ad-hoc network can be deployed in remote geographical locations and requires minimum setup and administration costs [1]. Moreover, the integration of an ad-hoc network with a bigger network-such as the Internet-or a wireless infrastructure network increases the coverage area and application domain of the ad-hoc network. However, communication in an ad-hoc network between different hosts that are not directly linked is an issue not only for search and rescue operations, but also for educational and business purposes [6].
The main aim of this chapter is to give an overview about mobile ad hoc networks. The rest of the chapter is organized as follow: Section 2.2 presents basic concepts of ah hoc network, while the types of ah hoc networks is presented in Section 2.3. Section 2.4 presents the features of ah hoc network, while the application of mobile ah hoc networking is presented in Section 2.5. The benefits of ad hoc network are presented in Section 2.6, while the Section 2.7 presents the drawbacks. And finally, some concluding remarks are presented in Section 2.8.
Basic Concepts of Ad Hoc Networks
The term Ad hoc Networking describes an automatic communications structures with a dynamic topology and self- organizing capability. The main idea behind ad hoc networks is that each node acts both as a host and as a router. Nodes that cannot establish a point-to-point connection because they are too distant relay packets to intermediate nodes which act as routers. Packets travel from the source to the destination hopping from node to node in a multi-hop fashion. Nodes that can communicate directly are called neighbours [4]. The Figure 2.1 shows the block diagram of mobile node acting both as host and as a router.
Figure 2.1: Block diagram of mobile node acting both as host and as router.
Ad hoc networks do not need any fixed, pre-existing infrastructure (e.g. base stations), therefore it can be deployed everywhere, at any time, quickly and without any cost. Due principally to the lack of any centralized infrastructure, ad hoc networks are difficult to design, may not be reliable, and cannot guarantee an exhaustive coverage: nodes may not be reachable and the network may be partitioned [4].
Ad hoc networks are dynamic networks. Nodes are free to move and network topology is always changing. Rapidity of topological changes is one of the biggest issues to take into consideration while designing an ad hoc network and fast changes are the main cause of performance deterioration. In other definition, a mobile ad hoc network (MANET) is a set of wireless mobile nodes that cooperatively form a network without specific user administration or configuration [5].
Figure 2.2, shows a simple ad-hoc network with three nodes. The outermost nodes are not within transmitter range of each other. However the middle node can be used to forward packet between the outermost nodes. The middle nod is acting as a router and the three nodes have formed an ad-hoc network.
Figure 2.2: Basic infrastructure of ad hoc network.
Types of Ad hoc Networks
Wireless Ad hoc networks have two major types-one is called Mobile Ad hoc Networks (MANETs) and another one is called Wireless Ad hoc Sensor Network, which can be describe as follows:
Mobile Ad hoc networks (MANETs)
A mobile ad hoc network (MANET) is a type of wireless ad hoc network, and is a self-configuring network of mobile devices connected by any number of wireless links. Every device in a MANET is also a router because it is required to forward traffic unrelated to its own use. Each MANET device is free to move independently, in any arbitrary direction, and thus each device will potentially change its links to other devices on a regular basis. The primary challenge for building a MANET is for each device to continuously maintain the information required to properly route traffic [7]. Such networks may operate in a standalone fashion, or may be connected to the larger Internet.
MANET are special cases of several other types of wireless and mesh networks, but have some key differences, at least in common usage, as listed below:
· Wireless ad hoc networks – MANET are a type and subset of ad hoc networks, but MANET usually implies the creation of a routable networking environment on top of a Link Layer ad hoc network.
· Mesh networks – MANET are a subset of mesh networks, but many mesh networks are not mobile or are not even wireless (e.g. BGP).
· Wireless mesh networks – As above, MANET are a subset of wireless mesh networks, but many mesh networks are not mobile and are not designed to support mobility [4].
MANET is sometimes referred to as mobile mesh networks. MANETs have become a very popular research topic since the mid- to late 1990s due to the increasing availability of laptops and 802.11/Wi-Fi wireless networking. Many of the academic papers evaluate protocols and abilities assuming varying degrees of mobility within a bounded space, usually with all nodes within a few hops of each other, and usually with nodes sending data at a constant rate [4]. Different protocols are then evaluated based on the packet drop rate, the overhead introduced by the routing protocol, and other measures.
MANET can also be classified into three major types, which are:
· Vehicular Ad Hoc Networks (VANET)
· Intelligent vehicular ad hoc network (InVANET)
· Internet Based Mobile Ad-hoc Networks (iMANET)
Vehicular Ad Hoc Networks (VANET)
A Vehicular Ad-Hoc Network, or VANET, is a form of Mobile ad-hoc network, to provide communications among nearby vehicles and between vehicles and nearby fixed equipment, usually described as roadside equipment [12].
The main goal of VANET is providing safety and comfort for passengers. To this end a special electronic device will be placed inside each vehicle which will provide Ad-Hoc Network connectivity for the passengers. This network tends to operate without any infra-structure or legacy client and server communication. Each vehicle equipped with VANET device will be a node in the Ad-Hoc network and can receive and relay others messages through the wireless network. Collision warning, road sign alarms and in-place traffic view will give the driver essential tools to decide the best path along the way [4 12].
There are also multimedia and internet connectivity facilities for passengers, all provided within the wireless coverage of each car. Automatic payment for parking lots and toll collection are other examples of possibilities inside VANET.
Most of the concerns of interest to MANets are of interest in VANets, but the details differ. Rather than moving at random, vehicles tend to move in an organized fashion. The interactions with roadside equipment can likewise be characterized fairly accurately. And finally, most vehicles are restricted in their range of motion, for example by being constrained to follow a paved highway [4].
Intelligent Vehicular Ad Hoc Networks (InVANET)
Intelligent vehicular ad hoc networks (InVANETs) use WiFi IEEE 802.11 and WiMAX IEEE 802.16 for easy and effective communication between vehicles with dynamic mobility. Effective measures such as media communication between vehicles can be enabled as well methods to track automotive vehicles. InVANET is not foreseen to replace current mobile (cellular phone) communication standards [6].
Automotive vehicular information can be viewed on electronic maps using the Internet or specialized software. The advantage of WiFi based navigation system function is that it can effectively locate a vehicle which is inside big campuses like universities, airports, and tunnels. InVANET can be used as part of automotive electronics, which has to identify an optimally minimal path for navigation with minimal traffic intensity [7]. The system can also be used as a city guide to locate and identify landmarks in a new city.
Communication capabilities in vehicles are the basis of an envisioned InVANET or intelligent transportation systems (ITS). Vehicles are enabled to communicate among themselves (vehicle-to-vehicle, V2V) and via roadside access points (vehicle-to-roadside, V2R). Vehicular communication is expected to contribute to safer and more efficient roads by providing timely information to drivers, and also to make travel more convenient [6 7]. The integration of V2V and V2R communication is beneficial because V2R provides better service sparse networks and long distance communication, whereas V2V enables direct communication for small to medium distances/areas and at locations where roadside access points are not available.
Currently there is ongoing research in the field of InVANETs for several scenarios. The main interest is in applications for traffic scenarios, mobile phone systems, sensor networks and future combat systems. Recent research has focused on topology related problems such as range optimization, routing mechanisms, or address systems, as well as security issues like traceability or encryption [12]. In addition, there are very specific research interests such as the effects of directional antennas for InVANETs and minimal power consumption for sensor networks. Most of this research aims either at a general approach to wireless networks in a broad setting or focus on an extremely specific issue.
Internet Based Mobile Ad Hoc Network (iMANET)
Internet Based Mobile Ad-hoc Networks (iMANET) are basically Networks in which Mobile Nodes (ad-hoc network) and Fixed Nodes (for providing internet) are present. Fixed nodes are gateways. In such type of networks normal ad-hoc routing algorithms don’t apply directly [4].
Mobile Ad hoc Sensor Networks
A mobile Ad hoc sensor network consists of a number of sensor spread across a geographical area. Each sensor has wireless communication capability and some level of intelligence to process signals and to transmit data. Unlike typical sensor networks, which communicate directly with the centralized controller, a mobile ad-hoc sensor network follows a broader sequence of operational scenarios, thus demanding a less complex setup procedure. In order to support routed communications between two mobile nodes, the routing protocol determines the node connectivity and routes packets accordingly. This makes a mobile ad-hoc sensor network highly adaptable so that it can be deployed in almost all environments [3].
Mobile ad-hoc sensor networks are very beneficial in different scenarios. These networks advance operational efficiency of certain civilian applications. For example, in a military operation, it can be used to gather information about enemy location, movement, etc. As a mobile traffic sensor networks, it can be used to monitor vehicle traffic on motorways, and as a mobile surveillance sensor network, it can be used for providing security in various places such as shopping malls, hotels, and in other similar facilities. Mobile ad-hoc sensor networks can also be use to locate free and occupied spots in a parking area and to monitor environmental changes in places like forests, oceans, etc [3 4].
Two ways to classify mobile Ad hoc sensor networks are whether or not the nodes are individually addressable, and whether the data in the network is aggregated. The sensor nodes in a parking lot network should be individually addressable, so that one can determine the locations of all the free spaces. This application shows that it may be necessary to broadcast a message to all the nodes in the network. If one wants to determine the temperature in a corner of a room, then addressability may not be so important. Any node in the given region can respond. The ability of the sensor network to aggregate the data collection can greatly reduce the number of message that need to be transmitted across the network [3].
The mobile ad-hoc sensor network is a new invention with long-term potential for transforming our daily lives. In mobile ad-hoc sensor networks, each host may be equipped with a variety of sensors that can be organized to detect different local events. Moreover, an ad-hoc sensor network offers low setup and administration costs. We can expect to see their deployment on a wide scale in the near future [4].
Features of Ad Hoc Network
Wireless, or single-hop networks, until recently were based on a fixed structure, basically network nodes communicating to fixed infrastructure. Mobile ad-hoc networking offers multi-hop communication, in effect network nodes communicating via other nodes. So, we find some features of Ad hoc network, which can be describe as follows:
Mobility
Mobile ad-hoc networks are highly dynamic. Node mobility introduces certain scalability problems in mobile ad-hoc network protocols. When network topology changes frequently, control messages have to be sent between nodes so that new routes are found and propagated throughout the network. Rapid deployment in areas with no infrastructure often implies that the users must explore an area and perhaps form team that in turn coordinate among themselves to create a taskforce or a mission [1]. We can have individual random mobility, group mobility, motion along replanned router etc. The mobility model can have major impact on the selection of a routing scheme and can thus influences performance.
Self Organization
Since network infrastructure is not available, the nodes must organize and maintain the network by themselves. Node is both a host and a router .A node may want to connect to a node that is out of single-hop distance, thus routing function is necessary for each node since there is no infrastructure support [7]. Moreover, the ad hoc network must autonomously determine its own configuration parameters including: addressing, routing, clustering, position identification, power control etc. In some cases, special nodes (e.g. mobile backbone nodes) can coordinate their motion and dynamically distribute in the geographic area and provide coverage of disconnected island.
Network Topology
Topology changes when nodes are mobile, new nodes join in, some nodes leave, or some routes break down. Frequent, temporary, and unannounced loss of network connectivity is common [7]. In such environments, it’s reasonable to expect that when topology changes happen there might be a short period where a lot of control messages will propagate across the network to distribute the new destination paths. Therefore, the protocol designer should make provision for highly dynamic and fast adapting algorithms that minimize control messages, and attempt to utilize long-lived routes to the maximum extent.
Minimising control messages is also essential, because of the additional load they place in the bandwidth-constrained wireless links. There’s at least an order of magnitude difference between wired and wireless data rates, with the former having a standardised 100 megabits/sec in a local Ethernet, and the latter having a nominal bit rate of 10Mbit/sec in the best case. The techniques used to reduce control messages must strike a balance between the minimum amount of messages and flooding the network each time the topology changes by keeping network state information in each node [7].
The former has the side effect that in an ever changing network topology, stale routes will appear often. While when the latter is applied to a network containing nodes with high rate of mobility, it might result in control messages consuming all the available bandwidth. This could also lead to very slow network convergence where nodes contain either incomplete or out-of-date views of the network topology.
Multi-hop
Since each node can route traffic for the others, multi-hopping is possible. No default router available, every node acts as a router and forwards each other’s packets to enable information sharing between mobile hosts, Capacity of wireless technologies etc [6]. Multi-hopping is a desirable capability in ad hoc network because single-hop ad hoc network does not scale large, thus limiting the communications among the node [7]. Moreover ad hoc network exhibits multi-hops for obstacle negotiation, spectrum reuse, and energy conservation.
Power Constraint
Most ad hoc nodes (e.g. laptops, PDAs, sensors, etc.) have limited power supply and no capability to generate their own power (e.g. solar panels). Since nodes can be mobile, it cannot be line-powered but instead batteries power it [8]. Saving battery power in the participating nodes of a mobile ad-hoc network is an important challenge. In many kinds of mobile ad-hoc networks, mobile nodes usually rely on exhaustible means for providing energy, such as batteries. For these nodes, energy conservation suddenly becomes an important design decision.
Nodes with low battery power may decide to enter a power saving mode when they having nothing to send, or until another high priority event is generated. This behaviour might affect the way the whole network is operating, since each node is responsible for forwarding another node’s packets in addition to its own. If nodes decide to become “selfish” and break the collective and cooperative nature of mobile ad-hoc networking by not forwarding another node’s data, the mobile ad-hoc architecture is endangered. A multitude of other problems and design trade-offs are concerned with power utilization in such networks, and this particular area is becoming the focus of increased attention [8].
Variation in Scale
Design constraints that are specific to ad hoc net- working Autonomous and infrastructure-less. MANET does not depend on any established infrastructure or centralized administration. Each node operates in distributed peer-to-peer mode, acts as an independent router and generates independent data. Network management has to be distributed across different nodes, which brings added difficulty in fault detection and management Multi-hop routing .No default router available [7].
Peer-to-Peer
Direct communication between peers is mandatory. This means that the piece of software forming an ad hoc application has to interact directly, without using a central server. A physical infrastructure has no impact on the fulfilment of this aspect [7].
Collocation
All logical interactions between applications have to result in a physical interaction between users. This is called collocation. It means that in order to be called an ad-hoc application, the service has to be location-based [6].
Heterogeneity
Each node may have different capabilities. And in order to be able to connect to infrastructure-based network (to form a hybrid network); some nodes can communicate with more than one type of network. [6].
Application of Ad hoc Networking
Ad hoc wireless networks can be used wherever there is a need for establishing a networking environment for a limited duration of time. These networks provide tremendous opportunities and can be used in numerous situations, particularly where a communication infrastructure is nonexistent or difficult to establish within timing constraints.
Typical Application
Mobile ad hoc networks have been the focus of many recent research and development efforts. So far, ad hoc packer-radio networks have mainly been considered for military applications, where a decentralized network configuration is an operative advantage or even a necessity [1]. In the commercial sector, equipment for wireless, mobile computing has not been available at a price attractive to large markets. However, as the capacity of mobile computers increase steadily, the need for unlimited networking is also expected to rise. Commercial ah hoc networks could be used in situations where no infrastructure (fixed or cellular) is available. Examples include rescue operations in remote areas, or when local coverage must be deployed quickly at a remote construction site. Ad hoc networking could also serve as wireless public access in urban areas, providing quick deployment and exte4nded coverage [2]. The access points in networks of this kind could serve as stationary radio relay stations that perform ad hoc routing among themselves and between user nodes. Some of the access points would also provide gateways via which users might connect to a fixed backbone network at the loca level, ah hoc networks that link notebook or palmtop computer could be used to spread and share information among participants at a conference. They might also be appropriate for application in home networks where devices can communicate directly to exchange information, such as audio-video devices, alarms, and configuration updates. Perhaps the most far-reaching applications is this context are more or less autonomous networks of interconnected home robots that clean, do dished, mow the lawn, perform security surveillance, and so on [1].
Some people have been proposed ad hoc multi-hop networks (denoted sensor networks)-for example, for environment monitoring, where the networks could be used to forecast water pollution or to provide early warning of an approaching tsunami. Short-range ad hoc networks can simplify intercommunication between various mobile devices (such as a cellular phone and a PDA) by forming a personal area network (PAN), and thereby eliminate the tedious need for cables. This could also extend the mobility provided by the fixed network (that is, mobile Internet Protocol, or IP) to nodes further our in an ad hoc network domain. The Bluetooth system is perhaps the most promising technology in the context of personal area networking [1].
In Personal Area Network (PAN)
A network extension seen from the viewpoint of the traditional mobile network, a Bluetooth-based PAN opens up a new way of extending mobile networks into the user domain. Someone on a trip who has access to a Bluetooth PAN could use the General Packet Radio Service/Universal Mobile Telecommunication System (GPRS/UMTS) mobile phones a gateway to the Internet or to a corporate IP network. In terms of traffic load in the network, the aggregate traffic of the PAN would typically exceed that of the mobile phone [10]. In addition, if Bluetooth PANs could be interconnected with scatter-nets, this capacity would be increased. Figure 2.3 shows a scenario in which four Bluetooth PANs are used.
Figure 2.3: Personal Area Network (PAN) scenario
The PANs are interconnected via laptop computers with Bluetooth links. In addition, two of the PANs are connected to an IP backbone network, one via a local area network (LAN) access point and the other via a single GPRS/UMTS phone. A PAN can also encompass several different access technologies distributed among its member devices, which exploit the ad hoc functionality in the PAN. For instance, a notebook computer could have a wireless LAN (WLAN) interface (such as Institute of Electrical and Electronic Engineers [IEEE] 802.11 standards or HiperLAN/2) that provides network access when the computer is used indoors. Thus the PAN would benefit from the total aggregate of all access technologies residing in the PAN devices. As the PAN concept matures it will allow new devices and new access technologies to be incorporated into the PAN framework. It should also eliminate the need to create hybrid devices, such as PDA-mobile phone combination, because the PAN network will instead allow for wireless integration. In other word, it will not be necessary to trade off form for function. In all the scenarios discussed above it should be emphasized that close-range radio technology, such as Bluetooth, is a key enabler for introducing the flexibility represented by the PAN concept [10].
Search-and-Rescue Applications
When we face an unfortunate situation such as an earthquake, hurricane, or similar disaster, ad hoc wireless networks can prove to be very useful in search-and-rescue operations. In general, disasters leave a large population without power and communication capabilities for they destroy the infrastructures. Ad hoc wireless networks can be established without such infrastructures and can provide communications information, and take an action that they are programmed to do. A smart dress may be programmed to monitor certain conditions and vital signs of an individual on a regular basis. This could become very useful for defence personnel in combat situations. The monitored information can be processed, and appropriate action can be taken by the dress, if needed. A smart dress may even be able to indicate the exact location of the problem [10].
Health Care Applications
Exchanging multimedia (audio, video, and data) information between a patient and health care facilities is very helpful in critical and emergency situations. An individual who is being transported to a hospital by an ambulance may exchange information using ad hoc communication networks. A health care professional, in many situations, is in a much better position to diagnose and prepare a treatment plan for an individual if he or she has video information rather than just audio or data information [10]. For instance, video information may be helpful in assessing the reflexes and viewing the coordination capability of a patient. Similarly, the level of injuries of a patient can be established better with visual information than with just audio or other descriptive information. Real-time ultrasound scans of a patient’s kidneys, heart, or other organs may be very helpful in preparing a treatment plan for a patient who is being transported to a hospital, prior to his or her arrival in the hospital. Such information can be transmitted through wireless communication networks, from an ambulance to hospital or to other health care professionals who are currently scattered at different places but are converging toward the hospital for treating the patient being transported [1].
Ah hoc wireless networks established within a (smart) home can also be very useful for monitoring homebound patients. Such homes may be able to make some basic decisions (based on information exchanged between various sensors participating in an ad hoc network) that are beneficial to the elderly population. Some of the actions that smart homes can take include monitoring the movement patterns inside a home, recognizing a fall of a human being, recognizing an unusual situation, and informing a relevant agency so that appropriate help can be provided, if needed. The concept of a smart dress, discussed in the subsection on defence applications (above), can also be used to monitor health conditions of patients. Such dresses may become very useful for providing heath care for our elderly population [10].
Academic Environment Applications
Most of the academic institutions either already have wireless communication networks or are in the process of establishing such facilities. Such an environment provides students and faculty a convenient to interact and accomplish their mission. Ad hoc wireless networks can enhance such an environment and add many attractive features. For instance, an ad hoc wireless communication network can be established among the instructor and the students enrolled in his/her class. Such a setting can provide an easy and convenient mechanism for instructor to distribute handouts to all the students in the class and also for students to submit their assignments. Sharing information among the class participants can be as easy as click of a key on the keyboard. Due to the aura of mobility attached with the ad hoc wireless networks, such networks can also be established while on a field trip and industrial visits. Staying in touch cannot be any easier than this [10].
Industrial Environment Applications
Most industrial or corporate sites have wireless communication networks in place, particularly in manufacturing environments. Manufacturing facilities, in general, have numerous electronic devices that are interconnected. Having wired connectivity leads to cluttering and crowding of space, which not only pose safety hazards but also adversely affect reliability. Use of wireless communication networks eliminates many of these concerns. If the connectivity is in the form of ad hoc wireless communication networks, that adds many attractive aspects, including mobility. The devices can be easily relocated, and the networks reconfigured based on the requirements as they arise. At the same time, communication among various communicating entities can be maintained, and corporate meetings can take place without employees gathering in the same room [10].
Drawbacks of Ad Hoc Networks
Medium access control, Routing, security, limited bandwidth, and low power are some of the important challenges to the technology [7]. As far as low power is concerned, it’s more of a hardware issue. However, it does effect the other operations of the ad-hoc network. In this section summarizes the technical problem that faces in ad hoc network mow
Medium Access Control
A packet collision over the air is much more severe in multi-hop environments than that in wireless LANs. Packet losses due to MAC layer contention will definitely affect the performance of the high layer networking schemes such as the TCP congestion control and routing maintenance because a node does not know whether an error is due to the collision or the unreachable address. It has been shown that multi-hop ad hoc networks perform poorly with TCP traffic as well as heavy UDP traffic [6].
The source of the above problems comes mainly from the MAC layer. The hidden terminals may introduce collision and the exposed terminals may lead to low throughput efficiency. In addition to these two notorious problems, the receiver blocking problem (i.e., the intended receiver does not respond to the sender with CTS or ACK due to the interference or virtual carrier sensing operational requirements for the other ongoing transmissions) also deserves serious consideration. In facet, this problem becomes more severe in multi-hop environments and results in throughput inefficiency and starvation of some traffic flows or nodes. The next few subsections describe a few problems in multi-hop mobile ad hoc networks when the IEEE 802.11 MAC protocol is deployed [7].
Hidden Terminal Problem
Figure 2.4: Hidden terminal problem
The shared wireless environment of mobile ad hoc networks requires the use of appropriate medium access control (MAC) protocols to mitigate the medium contention issues, allow efficient use of limited bandwidth, and resolve so-called hidden and exposed terminal problems. These are basic issues, independent of the support of QoS; the QoS requirements add extra complexities for the MAC protocols. The issues of efficient use of bandwidth and the hidden/exposed terminal problem have been studied exhaustively and are well understood in the context of accessing and using any shared medium. We briefly discuss the “hidden-terminal” problem as an issue especially pertinent for the wireless networks [7].
Consider the scenario of Fig. 2.4, where a barrier prevents node B from receiving the transmission from D, and vice versa, or, as usually stated, B and D cannot “hear” each other. The “barrier” does not have to be physical; a large enough distance separating two nodes is the most commonly occurring “barrier” in ad hoc networks. Node C can “hear” both B and D. When B is transmitting to C, D, begin unable to “hear” B, may transmit to C as well, thus causing a collision and exposing the hidden-terminal problem. In this case, B and D are “hidden” from each other.
Exposed Terminal Problem
An exposed terminal is the one within the sensing range of the transmitter but not within that of the receiver. The exposed node senses the medium busy and does not transmit when the transmitter transmits, leading to bandwidth under-utilization.
Figure 2.5: Exposed terminal problem
In Fig 2.5, F is the exposed terminal to A when A is transmitting to B. F senses A’s transmission and keeps silent, although F can transmit to other nodes outside of A’s sensing range without interfering with B’s reception.
In fact, in the four-way handshake procedures in IEEE 802.11 MAC, either RTS and CTS or DATA and ACK bidirectional packets are exchanged. Thus, the exposed node of one transmitter-receiver pair is also the hidden node of the other pair. So, in addition to the hidden terminal, the exposed terminal of the transmitter should not initiate any new transmission during the whole transmission process to avoid collision with the short packets ACK or CTS in IEEE 802.11 MAC. Thus, the carrier sensing strategy based on the RTS/CTS handshake will lead to a significant deficiency in spatial reuse [7].
Routing Misbehaviour
Routing in mobile ad-hoc networks is achieved through mobile nodes acting as intermediate nodes. These nodes are responsible for receiving and forwarding data packets from one host to another in the network. The absence of a fixed infrastructure makes routing a challenge in a mobile ad-hoc environment.
There are also several other issues which have an effect on the overall performance of the mobile ad-hoc network. Some of these issues include bandwidth constraints, hidden terminal problems, security and limited battery power of the participating nodes. These issues are somehow interrelated with the overall routing mechanism. In order to gain a better routing solution, it’s almost always required to address these issues in conjunction with the routing problem of the mobile ad-hoc network.
Within the traditional routing mechanism, there are also several other issues to consider. For example, a node can become selfish and refuse to forward data packets to other nodes; or the node fails to forward data packets to the destination node. Finally, a node could enter an inactive state because of a limited power supply. These are some of the issues can result in communication breakdowns and can eventually lead us to an abnormal network environment [10].
Limitation of Battery Power
Limitation on the battery power of the mobile nodes is another basic issue for ad hoc networking. Limited battery power restricts the transmission range (hence the need for each node to act as a router) as well as the duration of the active period for the nodes. Below some critical thresholds for battery power, a node will not be able to function as a router, thus immediately affecting the network connectivity, possibly isolating one or more segments of the network. Fewer routers almost always mean fewer routes and, therefore, increased likelihood of degraded performance in the network. Indeed, QoS obviously becomes meaningless if a node is not even able to communicate, owing to low battery power. Since exchange of messages necessarily means power consumption, many ad hoc networking mechanisms, especially routing and security protocols, explicitly include minimal battery power consumption as a design objective.
Again, power is a costly resource in mobile devices. And networking is one of the most energy consuming operations [8]. According to an experiment by Kravets and Krishnan (1998), power consumption caused by networking related activities is approximately 10% of the overall power consumption of a laptop computer. This figure rises up to 50% in handheld devices! The aim of saving power in infrastructure-based network is to minimize energy consumption in the hosts/nodes. The tactic is to move the communication and computation efforts to the fixed infrastructure, thus keeping the network interface of the devices in inactive or sleep state as long as possible. In ad hoc network every node has to contribute to maintain the network connections. Hence the aim of minimizing energy consumption of each node is inadequate. An additional aim is to maximize network lifetime [8].
Security Problems
There are two types of security attack: passive and active. In a passive attack, a malicious node either ignores operations supposed to be accomplished by it (examples: silent discard, partial routing information hiding), or listens to the channel, attempting to retrieve valuable information (example: eavesdropping) [5]. In both cases the malicious node does not insert any message to the network [5]. It is hard to decide ignorance to operations from normal network failures in ad hoc networks. As for active attack, information is inserted to the network and thus the network operation or some nodes may be harmed [7]. Examples are impersonation/spoofing, modification, fabrication and disclosure attack. The security mechanisms to counter the above attacks can be ‘preventive’ by using key-based cryptography, or ‘detective’. Key distribution is at the canter of preventive mechanisms. Explain in the following section. Since no central authority, no centralized trusted third party, and no central server are available in ad hoc network, key management has to be distributed over the nodes. On the other hand, the intrusion detection system (IDS) in detective mechanisms has to monitor and rely on the audit trace that is limited to communication activities taking place within the radio range (i.e. partial and localized information) [7].
Conclusion
In Ad Hoc Network basic section, it has been discussed about basic of ad hoc network, feature of ad hoc network, ad hoc application features, benefit of ad hoc network, and draw back of ad hoc network.
Ad hoc networks are dynamic networks: nodes are free to move and network topology is always changing. The main idea behind ad hoc networks is that each node acts both as a host and as a router. Nodes that cannot establish a point-to-point connection because they are too distant relay packets to intermediate nodes which act as routers. Packets travel from the source to the destination hopping from node to node in a multi-hop fashion. Nodes that can communicate directly are called neighbours.
Ad hoc networks are a new wireless networking paradigm for mobile hosts. Ad hoc networks features are infrastructure, router and self-organizer, network topology, multi-hop, power constraint, variation in scale and heterogeneity.
Ad hoc applicationas a self-organizing application composed of mobile and autonomous devices, interacting as peers and which relationships are made pos-sable because of relative physical distance. More formally, three basic features must be present which are mobility, peer- to-peer, and collocation.
In ad hoc network have benefits to the users, communication network operators and service providers. Medium access control, Routing, security, limited bandwidth, and low power are some of the important challenges to the technology. As far as low power is concerned, it’s more of a hardware issue. The technical problem, faces in ad hoc network such as medium access control, routing, power conservation, security etc.
Ad hoc network is not a one-size-fit-all measure, its’ have some limitations such as- Killer application has not turned out, another is acceptance by users is unclear, scalability remains unknown, and delay caused by multi-hopping. The channel is unprotected from outside signals. Hidden-terminal and exposed-terminal phenomena may occur.
Security Issues
In ad hoc networks the communicating nodes do not necessarily rely on a fixed infrastructure, which sets new challenges for the necessary security architecture they apply. In addition, as ad hoc networks are often designed for specific environments and may have to operate with full availability even in difficult conditions, security solutions applied in more traditional networks may not directly be suitable for protecting them. However, MANETs are vulnerable to different attacks due to its fundamental characteristics such open medium, dynamic topology, absence of central administration, distributed cooperation, and constrained capability. In this chapter we introduce security attacks on mobile ah hoc networks as well as some security requirements of ad hoc network.
Introduction
Ad hoc networks may be very different from each other, depending on the area of application. For instance in a computer science classroom an ad hoc network could be formed between students’ PDAs and the workstation of the teacher. In another scenario a group of soldiers is operating in a hostile environment, trying to keep their presence and mission totally unknown from the viewpoint of the enemy. The soldiers in the group work carry wearable communication devices that are able to eavesdrop the communication between enemy units, shut down hostile devices, divert the hostile traffic arbitrarily or impersonate themselves as the hostile parties. As can obviously be seen, these two scenarios of ad hoc networking are very different from each other in many ways: In the first scenario the mobile devices need to work only in a safe and friendly environment where the networking conditions are predictable. Thus no special security requirements are needed. On the other hand, in the second and rather extreme scenario the devices operate in an extremely hostile and demanding environment, in which the protection of the communication and the mere availability and operation of the network are both very vulnerable without strong protection [3].
Security is an important issue for ad hoc networks, especially for those security-sensitive applications. To secure an ad hoc network, we consider the following attributes: availability, confidentiality, integrity, authentication, and non-repudiation .Ad hoc wireless network does not have any predefined infrastructure. Considering this principal to the lack of any centralized infrastructure, difficult to establish security ad hoc networks thus it is obvious that with lack of infrastructural support and susceptible wireless link attacks, security in ad hoc network becomes inherent weakness [3].
The main objective of this chapter is to give an overview of how the area of application affects the security requirements of ad hoc networks. The focus of the discussion is in security issues in MANETs.
The rest of this chapter is designed as follows: Section 3.2 introduces to the readers about the vulnerabilities against ad hoc network, while Section 3.3 presents various types of attacks against ad hoc networks. Section 3.4 presents different types of attacks against routing layer of MANETs, where security requirements of MANETs are presented in Section 3.5. Section 3.6 presents some problems to provide security in ad hoc networks. And finally, some concluding remarks are presented in Section 3.7.
Vulnerabilities against MANETs
While a wir