SECURITY PROBLEMS PERTAINING TO E-CONTENT INFORMATION FLOW IN WIRELESS MOBILE AD-HOC NETWORKS. P. Balagangadhar Rao INDIA

Security strength and network performance are the two sides of a coin. If, one of these is enhanced, the other will suffer. Achieving a good trade-off between these two extremes is a fundamental challenge in security design for mobile ad-hoc networks which are basically self-organized wireless interconnecting communication devices that would either extend (or) operate in concert with the wired networking infrastructure INTRODUCTION:

 Lot of research is going on in this field in respect of the unique characteristics of ad-hoc networks such as open peer-to-peer network architecture, shared wireless medium, highly dynamic topology and stringent resource constraints. These limitations make a strong case for building multi-fence security solutions that meet both the goals of security as well as desirable network performance. Ad-hoc networks can be established on demand and disappear when there is no need, traditional security solutions applicable to wired-networks will not be sufficient because of the inherent limitations of such networks. In such an open and distributed communication environment, a central authorization facility that makes more stringent security will not be available. Self organization in ad-hoc networks aims to bring orderliness to the evolving distributed systems with the least possible human intervention. The three important characteristics of such a self organized systems are - I.P (Internet Protocol) auto-configuration, peer-to- peer networking, and shared open-content web pages. The fundamental security problem in mobile ad-hoc network is: the protection of its basic functionality to deliver the "data bits" from one node to the other. Unlike wired networks that have dedicated routers, each mobile node in an ad- hoc network will function as a router and forward packets to other peer nodes.

 Two basic approaches to protect mobile ad-hoc networks are: proactive and reactive. In this paper, an attempt is made to discuss certain fundamental security design challenges like denial-of-service attacks, providing link-layer security support, protecting routing and forward protocol, secured authentication and end-to-end communication through data encryption, preventing viruses, worms and application abuses, at different layers in a wireless ad-hoc network.

 Keywords: Mobile Ad-hoc Networks, Q.O.S. (quality of service), Security Solutions, Net- Work Layers, Link-layer, Viruses, Worms, Nodes

 Mobile ad-hoc network is an autonomous system of mobile nodes connected by wireless links. Each node operates as an end system and a router for all other nodes in the network. Since the nodes are mobile, the network topology may change rapidly and unpredictably over time. The network is decentralized where all network activity including discovering the nodes themselves must execute the topology and delivering messages. This implies that the routing of message in the form of “bits” is also to be ensured by the mobile node

. The design of network protocols for these networks is a complex issue Preservation of security, latency, reliability, recovery from failure or significant factors that are to be considered while designing the algorithms for these networks.Security has become a primary concern in order to provide protected communication between nodes in a potentially hostile environment.Security services such as authentication, confidentiality, integrity, anonymity and availability are the ultimate goals of the security solutions for mobile ad-hoc networks. In order to achieve these goals, the security solutions should be provided in the entire protocol stack. Quality-of- service(Q.O.S) is measure of performance of a system or network.  Viruses, Worms are software programmes by hackers in order to destroy or steal or damage or intrude into the data of others, in an unauthorized way. Network-Layers are various functionalities in a computer network.

 SECURITY SOLUTIONS: (a) Preventing signal jamming and denial of service attacks at Physical layer level. (b) Protecting the wireless MAC (medium access control) protocol and providing link-layer security support at Link layer level. (c) Protecting the ad-hoc routing and forwarding protocols at Network layer level. (d) Authenticating and securing end-to-end communications through data encryption at Transport layer level. (e) Detecting and preventing viruses, worms, malicious codes and application abuses at Application layer level. By ensuring above mentioned security solutions at different layers of mobile ad-hoc networks, we can securely transport e-content information flow.

 CHALLENGES: As there will not be any dedicated routers as in the case of wired networks, each mobile node in an ad- hoc network should function as a router and forward packets of information to other peer nodes. We should make a note of the accessibility of wireless channel to both legitimate network users and malicious attackers, equally. There is no well defined place where traffic monitoring or access control mechanisms can be deployed.As a result, the boundary that separates the inside network from the outside world becomes thin.

 The existing protocols assume a trusted and co-operative environment. As a result, a malicious attacker can readily become a router and disrupt network operations by intentionally disobeying the protocol specifications. There are basically to approaches to protect such networks. The first one is “proactive” where as the other one is “reactive”.

 The proactive approach attempts to prevent an attacker from launching attacks in the first place, typically through various cryptographic techniques. In contrast, the reactive approach reacts, suitably, after detecting a security threat. A complete security solution should integrate both these approaches for preventing, detecting and reacting to security threats. Security is a chain, and it is only as secure as that of the weakest link.

 CONSTRAINTS: The stringent resource constraints in mobile ad-hoc networks constitute another serious challenge to security design. The wireless channel is bandwidth constrained and shared among multiple network entities. The computational capability of certain type of mobile nodes is limited. For example, such as PDAs (Personnel Digital Assistance), can hardly perform computation-intensive tasks like asymmetric cryptographic computation. As mobile devices are typically powered by batteries, they may have limited energy availability. The network topology is highly dynamic as nodes as nodes frequently join or leave the network, and roam in the network on their own will. The wireless channel is subject to interferences like co-channel interference or adjacent channel interference, thus prone for errors. The security scheme adopted by each device has to work with in its own resource limitations and is a challenging job because of the limited wireless transmission range, broad cast nature of wireless, node mobility, limited power resource.

 Mobile users may request at any time, any where, the security services as they move from one place to another. The above characteristics of mobile ad-hoc networks clearly make a case for building multifence security solutions that achieve both broad protection and desirable network performance, simultaneously. As there is no well defined place/infrastructure where we can deploy a single security solution, the deployment of security is not a trivial task. Moreover, portable devices, as well as the system security information they store, are vulnerable to compromise or physical capture, especially low-end devices with weak protection. Attackers may sneak into the network through these weak links and incur a serious damaging effect of security breaches in the system.

 CONCLUSION: Security never comes free. When more security features are introduced into the network, the result is the ever- increasing computation, communication, and management overhead. Consequently, network performance in terms of scalability, service availability, robustness, and so on of the security solutions, becomes an important concern in a resource-constrained ad-hoc network. While many contemporary proposals focus on the security stand point, the live the network performance aspect largely unaddressed.In fact, both dimensions of security strength and network performance are equally important, and achieving a good trade-off between the two extremes is the real challenge in security design for mobile ad-hoc networks

 Advantages of using an ad-hoc wireless networks include easy and speedy deployment It is robust, adaptive and self – organizing network. Designing a secure ad-hoc wireless communication is a challenging task due to (1) insecure wireless communication links (2)Absence of a fixed infrastructure (3)resource constraints like battery power, band width, memory, CPU (central processing unit of a computer) capacity. (4)Node mobility that triggers a dynamic network topology

 The main requirements of a robust security routing protocol are (1) Detection of malicious nodes. Avoiding routing of e-content packets from such nodes (2)Guarantee of correct route to destination computer(3)Confidentiality of network topology to prevent attacks by an attacker on the weak links(4)Stability against attacks so that the routing protocol must be able to resume the normal operation with in a reasonable time after an attack

 By addressing the above problems, we can ensure seamless e –content information flow in ad-hoc mobile networks