Wireless Networks Security
With current advances in technology, wireless networks are increasing in popularity. These networks allow users the freedom to travel from one location to another without interruption of their computing services. Ad hoc networks, a subset of wireless networks, allow the formation of a wireless network without the need for access point. Technology under development for wireless ad hoc networks has rapidly become an indispensable part of our life since it provides “anytime, anywhere” networking services for mobile users. Wireless ad hoc networks can be dynamically set up without relying on any pre-existing infrastructure, such as Public Key Infrastructure, and central administration for communications. However, such infrastructureless feature of the networks also makes them vulnerable to security attacks. Several protocols have been proposed in order to achieve a high degree of security based on a combination of human-mediated communication and an ordinary Dolev-Yao communication medium. One of which is the Symmetrised Hash Commitment Before Knowledge protocol or the SHCBK protocol ( A. W. Roscoe and Long Nguyen, 2006). The protocol design seeks to optimise the amount of security that the humans can achieve for a given amount of work.
Chapter 1
Introduction
Introduction
A wireless ad hoc network is a de-centralized wireless network. The network is called ad hoc for the reason that each hop is ready to send onward data for other hop, and so the resolving that which of hops will send the data to the forward hops is dynamically established on the network connectivity. This is in dissimilarity to wired networks in which routers execute the duty of routing. It is also in difference to organize the wireless networks. In which a particular node recognized as an admission point manages communication among other nodes. All taking part parties in an ad hoc network have the same opinion to recognize and forward messages, to and from each other. With this elasticity, wireless networks have the capability to form anyplace, at any occasion, as long as two or more wireless users are keen to communicate. Mobile nodes inside an ad-hoc network move from one location to another. However, finding ways to model these movements is not obvious. In order to evaluate an ad hoc network performance it is necessary to develop and use mobility models that accurately represent movements of the mobile nodes. In this paper we present performance evaluation of various entity mobility models in terms of the traveling patterns of mobile node.
Abstract— Mobile ad hoc network (MANET) is a self-configuring
network that is formed automatically via wireless links by a collection of mobile nodes without the help of a fixed infrastructure or centralized management. The mobile nodes forward packets for each other, allowing communication among nodes outside wireless transmission range hop by hop. Due to dynamic infrastructure-less nature and lack of centralized monitoring points, the ad hoc networks are vulnerable to attacks. Attacks on ad hoc network routing protocols disrupt network performance and reliability. This paper attempts to provide a comprehensive overview of attacks and secure routing. It first analyzes the reason that ad hoc network is vulnerable to attacks. Then it presents the well known attacks and the popular secure protocols. is out of its radio range, the cooperation of other nodes in the
network is needed; this is known as multi-hop communication. Therefore, each node must act as both a host and a router at the same time.
I. INTRODUCTION
In most wireless networking environments in productive use today the users' devices communicate either via some networking infrastructure in the form of base stations and a backbonenetwork,ordirectlywiththeirintended communication partner, e.g. using 802.11 in ad hoc networks
In contrast a mobile ad hoc network (MANET) is a self-configuring network that is formed automatically via wireless links by a collection of mobile nodes without the help of a fixed infrastructure or centralized management. Each node in mobile ad hoc networks is equipped with a wireless transmitter and receiver, which allow it to communicate with other nodes in its radio communication range [2]. Nodes usually share the same physical media; they transmit and acquire signals at the same frequency band, and follow the same hopping sequence or spreading code [3]. If the destination node is not within the transmission range of the source node, the source node takes help of the intermediate nodes to communicate with the destination node by relaying the messages hop by hop. Fig.2 illustrated the Mobile ad-hoc network. In order for a node to forward a packet to a node that
II. SECURITY ATTACKS
Securing wireless ad hoc networks is a highly challenging issue. Due to dynamic distributed infrastructure-less nature and lack of centralized monitoring points, the ad hoc networks are vulnerable to various kinds of attacks. Ad hoc networks have to cope with the same kinds of vulnerabilities as their wired counterparts, as well as with new vulnerabilities specific to the ad hoc context [8]. Furthermore, traditional vulnerabilities are also accentuated by the ad hoc paradigm. Firstly, the wireless channel is accessible to both legitimate network users and malicious attackers. The ad hoc networks are susceptible to attacks ranging from passive eavesdropping to active interfering. Secondly, the lack of an online CA or Trusted Third Party adds the difficulty to deploy security mechanisms. Thirdly, mobile devices tend to have limited power consumption and computation capabilities which make
it more vulnerable to Denial of Service attacks and incapable to execute computation-heavy algorithms like public key algorithms.Fourthly,inMANETs,therearemore probabilities for trusted node being compromised and then being used by adversary to launch attacks on networks; finally, node mobility and frequent topology changes enforce frequent networking reconfiguration which creates more chances for attacks, for example, it is difficult to distinguish between stale
routing information and faked routing information [9].
Ad hoc networks attacks can be classified as passive or active [10]. Passive attack signifies that the attacker does not send any message, but just listens to the channel. Passive attacks do not disrupt the operation of a protocol, but only attempts to discover valuable information. Active attacks may either being directed to disrupt the normal operation of a specific node or target the performance of the ad hoc network as a whole.
For passive attacks, the attacker listens to the channel and packets containing secret information (e.g., IP addresses, location of nodes, etc.)might be eavesdropped, which violates confidentiality. In a wireless environment it is usually impossible to detect this attack, as it does not produce any new traffic in the network.
Active attacks, including injecting packets to invalid destinations into the network, deleting packets, modifying the contents of packets, and impersonating other nodes violate availability, integrity, authentication, and non-repudiation. Unlike the passive attacks, active attacks can be detected and eventually avoided by the legitimate nodes that participate in an ad hoc network [11].
Certain active attacks can be easily performed against an ad
hoc network. Understanding possible form of attacks is always the first step towards developing good security solutions. Based on this threat analysis and the identified capabilities of the potential attackers, several well known attacks that can target the operation of a routing protocol in an ad hoc network are discussed.
• Impersonation. In this type of attack, nodes may be able to join the network undetectable or send false routing information, masquerading as some other trusted node.
• Wormhole. The wormhole attack involves the cooperation between two attackers [18]. One attacker captures routing traffic at one point of the network and tunnels them to another point in the network that shares a private communication link between the attackers, then selectively injects tunnel traffic back into the network. The two colluding attacker can potentially distort the topology and establish routes under the control over the wormhole link.
• Rushing attacks [19]. The ROUTE REQUESTs for this Discovery forwarded by the attacker are the first to reach each neighbor of the target, then any route discovered by this Route Discovery will include a hop through the attacker. That is, when a neighbor of the target receives the rushed REQUEST from the attacker, it forwards that REQUEST, and will not forward any further REQUESTs from this Route Discovery. When non-attacking REQUESTs arrive later at these nodes, they will discard those legitimate REQUESTs.
• Blackmail [20]. The attack incurs due to lack of authenticity and it grants provision for any node to corrupt other node's legitimate information. Nodes usually keep information of perceived malicious nodes in a blacklist. This attack is relevant against routing protocols that use mechanisms for the identification of malicious nodes and propagate messages that try to blacklist the offender. An attacker may fabricate such reporting messages and tell other nodes in the network to add that node to their blacklists and isolate legitimate nodes from the network [21].
III. SECURE ROUTING
The previously presented ad hoc routing protocols without security consideration assume that all participating nodes do not maliciously disrupting the operation of the protocol
[22][23]. However, the existence of malicious entities cannot be disregarded in any system, especially in open ones like ad hoc networks. Secure routing protocols cope with malicious nodes that can disrupt the correct functioning of a routing protocol by modifying routing information, by fabricating false routing information and by impersonating other nodes. These secure routing protocols for ad hoc networks are either completely new stand-alone protocols, or in some cases incorporations of security mechanisms into existing protocols. Generally the existing secure routing protocols that have been proposed can be broadly classified into two categories, those that use hash chains, and those that in order to operate require predefined trust relationships. This way, collaborative nodes can efficiently authenticate the legitimate traffic and differentiate the unauthenticated packets from outsider attackers.
• SEAD [20]. Secure Efficient Ad hoc Distance vector routing protocol (SEAD), a secure ad hoc network routing protocol based on the design of the Destination-Sequenced Distance-Vector routing protocol(DSDV) [24]. To support use of SEAD with nodes of limited CPU processing capability, and to guard against modification of the source address for a routing update and attacks in which an denial of service attacks attempts to cause other nodes to consume excess network bandwidth or processing time, efficient one-way hash
chains but not cryptographic operations are used in the authentication of the sequence number and the metric (hop count) field of a routing table update message.
When a node in SEAD sends a routing update, the node includes one hash value from the hash chain with each entry in that update. The nodes sets the destination address in that entry to that destination node's address, the metric and sequence number to the values for that destination in its routing table, and the hash value to the hash of the hash value received in the routing update entry from which it learned that route to that destination.
When a node receives a routing update, for each entry in that update, the node checks the authentication on that entry, using the destination address, sequence number, and metric in the received entry, together with the latest prior authentic hash value received by this node from that destination's hash chain. The hash value of each entry is hashed the correct number of times and it is compared to the previously authenticated value. Depending on this comparison the routing update is either accepted as authenticated, or discarded.
• Ariadne [25]. Ariadne is a secure on-demand ad hoc routing protocol based on DSR that prevents attackers or compromised nodes from tampering with uncompromised routes consisting of uncompromised nodes, and also prevents many types of Denial-of-Service attacks. In addition, Ariadne uses only highly efficient symmetric cryptographic primitives.
To convince the target of the legitimacy of each field in a ROUTE REQUEST, the initiator simply includes in the REQUEST a MAC (message authentication code) computed with key over unique data. The target can easily verify the authenticity and freshness of the ROUTE REQUEST using the shared key. One-way hash functions are used to verify that no hop was omitted which is called per-hop hashing. Three alternative techniques to achieve node list authentication: the TESLA protocol [26], digital signatures, and standard MACs. When Ariadne Route Discovery is used with TESLA, each hop authenticates the new information in the REQUEST. The target buffers and does not send the REPLY until intermediate nodes can release the corresponding TESLA keys. Ariadne Route Discovery using MACs is the most efficient of the three alternative authentication mechanisms, but it requires pairwise shared keys between all nodes. The MAC list in the ROUTE REQUEST is computed using a key shared between the target and the current node. The MACs are verified at the target and are not returned in the ROUTE REPLY. If Ariadne Route Discovery is used with digital signatures, the MAC list in the ROUTE REQUEST becomes a signature list.
• SRP [27].The Secure Routing Protocol (SRP) consists of several security extensions that can be applied to existing ad hoc routing protocols providing end-to-end authentication. The sole requirement of the proposed scheme is the existence of a security association between the node initiating the query and the sought destination. The security association is used to establish a shared secret between the two nodes, and the non-mutable fields of the exchanged routing messages are protected by this shared secret.The scheme is robust in the presence of a number of non-collud
ing nodes, and provides
• Routing Table Overflow. In a routing table overflow attack the malicious node floods the network with bogus route creation packets to non-existing nodes to overwhelm the routing-protocol implementations in order to consume the resources of the participating nodes and disrupt the establishment of legitimate routes. The goal is to create enough routes to prevent new routes from being created or to overwhelm the protocol implementation. Proactive routing protocols are more vulnerable to this attack, since they attempt to create and maintain routes to all possible destinations. A malicious node to implement this attack can simply send excessive route advertisements to the network. To implement this attack in order to target a reactive protocol like AODV is slightly more complicated since two nodes are required. The first node should make a legitimate request for a route and the malicious node should reply with a forged address [12].
• Sleep Depravation. The sleep deprivation torture aims at the consumption of resource of a specific node by constantly keeping it engaged in routing decisions [13]. This attack floods the network with routing traffic in order to consume battery life from the nodes and available bandwidth from the ad hoc network. The malicious node continually requests for either existing or non-existing destinations forces the neighbouring nodes to process and forward these packets and therefore consume batteries and network bandwidth hindering the normal operation of the network.
• Location disclosure. Location disclosure is an attack that targets the privacy requirements of an ad hoc network. Through the use of traffic analysis techniques [14] or with simpler probing and monitoring approaches an attacker is able to discover the location of a node, and the structure of the network. If the locations of some of the intermediary nodes are known, one can gain information about the location of the destination node as well.
• Routing table poisoning. Routing protocols maintain tables which hold information regarding routes of the network. In poisoning attacks the malicious nodes generate and send fabricated traffic, or modify legitimate messages from other nodes, in order to create false entries in the tables of the participating nodes [15]. Another possibility is injecting a RREQ packet with a high sequence number; this will cause that all other legitimate RREQ packets with lower sequence number will be deleted [16]. Routing table poisoning attacks can result in selection of non-optimal routes, creation of routing loops, bottlenecks and even partitioning certain parts
of the network.
• Black Hole [17]. A malicious node uses the routing protocol to inject false route replies to the route requests it receives advertising itself as having the shortest path to a destination whose packets it wants to intercept. Once the forged route has been established the malicious node is able to become a member of the active route and intercept the communication packets. Network traffic is diverted through the malicious node for eavesdropping, or attract all traffic to it in order to perform a denial of service attack by dropping the received packets or the first step to a man-in-the-middle attack.
While the security requirements for ad hoc networks are the same the ones for fixed networks, namely availability, confidentiality, integrity, authentication, and non-repudiation
[4] mobile wireless networks are generally more vulnerable to information and physical security threats than fixed wired networks [5]. Securing wireless ad hoc networks is particularly difficult for many reasons including vulnerability of channels and nodes, absence of infrastructure, dynamically changing topology and etc. [6]. The wireless channel is accessible to both legitimate network users and malicious attackers. The abstract of centralized management makes the classical security solutions based on certification authorities and on-line servers inapplicable. A malicious attacker can readily become a router and disrupt network operations by intentionally disobeying the protocol specifications.
The nodes can move randomly and freely in any direction and organize themselves arbitrarily. They can join or leave the network at any time [7]. The network topology changes frequently, rapidly and unpredictably which significantly changes the status of trust among nodes and adds the complexity to routing among the mobile nodes. The selfishness that nodes in ad hoc networks may tend to deny providing services for the benefit of other nodes in order to save their own resources (e.g., battery power) introduces new security issues that are not address in the infrastructure-based networks.
The rest of the paper is organized as follows: section 2 presents several secure attacks. Section 3 presents the popular secure protocols in ad hoc networks. In Section 4 conclusion
is presented.
Application
The decentralized nature of wireless ad hoc networks makes them suitable for a variety of applications where central nodes can't be relied on, and may improve the scalability of wireless ad hoc networks compared to wireless managed networks, though theoretical[2] and practical[3] limits to the overall capacity of such networks have been identified.
Minimal configuration and quick deployment make ad hoc networks suitable for emergency situations like natural disasters or military conflicts. The presence of a dynamic and adaptive routing protocol will enable ad hoc networks to be formed quickly.
Wireless ad hoc networks can be further classified by their application:
- mobile ad hoc networks (MANETs)
- wireless mesh networks
- wireless sensor networks.
Wireless security
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Wireless security is the prevention of unauthorized access or damage to computers using wireless networks.
Wireless networks are very common, both for organizations and individuals. Many laptop computers have wireless cards pre-installed. The ability to enter a network while mobile has great benefits. However, wireless networking has many security issues.[1] Hackers have found wireless networks relatively easy to break into, and even use wireless technology to crack into wired networks.
The risks to users of wireless technology have increased as the service has become more popular. There were relatively few dangers when wireless technology was first introduced. Crackers had not yet had time to latch on to the new technology and wireless was not commonly found in the work place. However, there are a great number of security risks associated with the current wireless protocols and encryption methods, and in the carelessness and ignorance that exists at the user and corporate IT level.[2] Cracking methods have become much more sophisticated and innovative with wireless. Cracking has also become much easier and more accessible with easy-to-use Windows-based and Linux-based tools being made available on the web at no charge.
Some organizations that have no wireless access points installed do not feel that they need to address wireless security concerns. In-Stat MDR and META Group have estimated that 95% of all corporate laptop computers that were planned to be purchased in 2005 were equipped with wireless. Issues can arise in a supposedly non-wireless organization when a wireless laptop is plugged into the corporate network. A cracker could sit out in the parking lot and break in through the wireless card on a laptop and gain access to the wired network.
accurate routing information in a timely manner. No assumption in SRP is made regarding the intermediate nodes, which may exhibit arbitrary and malicious behavior.
The SRP Header is integrated into the underlying protocol header structure as an additional IP option, and covers most parts of the routing protocol datagram. The source node sends
a route request with a query sequence (QSEQ) number that is
used by the destination in order to identify outdated requests,
a random query identifier (QID) that is used to identify the specific request, and the output of a keyed hash function. The destination node calculates the keyed hash of the request fields. If the output matches the SRP header MAC, the integrity of this request is verified, along with the authenticity of its origin. The destination generates a number of replies to valid requests, at most as many as the number of its neighbors, in order to disallow a possibly malicious neighbor to control multiple replies. For each valid request, the destination node places the accumulated route in the route reply packet and the QID and QSEQ of the route request in the corresponding SRP header fields, so that the source node can verify the freshness of the reply. Nodes use secure message transmission (SMT)
[28] to ensure successful delivery of data packets. In SMT, data messages are split into packets using secret sharing techniques so that if M out of N such packets are received, the message can be reconstructed.
SRP guarantees that fabricated, compromised, or replayed route replies would either be rejected or never reach back the querying node.
• ARAN [29]. The Authenticated Routing for Ad hoc Networks (ARAN) based on AODV is a stand-alone protocol that utilizes cryptographic public-key certificates signed by a trusted authority, which associates its IP address with a public key in order to achieve the security goals of authentication and non-repudiation. The protocol assumes that each node knows
a priori the public key of the certification authority that will be used to authenticate the other participating nodes.
ARANusescryptographiccertificatestobring authentication, message-integrity and non-repudiation to the route discovery process. The source node begins route instantiation to destination by broadcasting to its neighbors a route discovery packet (RDP). The RDP includes a packet type identifier, the IP address of the destination, the source node's certificate and a nonce, all signed with the source node's private key. When a node receives an RDP message, it sets up a reverse path back to the source by recording the neighbor from which it received the RDP. The receiving node uses the predecessor node's public key and certificate to validate the signature. The receiving node signs the contents of the message, appends its own certificate, and forward broadcasts the message to each of its neighbors. The signature prevents malicious nodes from injecting arbitrary route discovery packets that alter routes or form loops [30]. Eventually the RDP message is received, the destination unicasts a Reply (REP) packet back along the reverse path to the source. The REP includes a packet type identifier, the IP address of the source node, the certificate of the destination node . Nodes that receive the REP forward the packet back to
the predecessor from which they received the original RDP. Each node along the reverse path back to the source signs the REP and appends its own certificate before forwarding the REP to the next hop. When the source receives the REP, it verifies the destination's signature and the nonce returned by the destination. By using cryptographic certificates that guarantees end-to-end authentication, ARAN limits or prevents attacks that can afflict other insecure protocols. ARAN is a simple protocol that does not require significant additional work from nodes within the group but is as effective as AODV in discovering and maintaining routes. The cost of ARAN is larger routing packets, which result in a higher overall routing load, and higher latency in route discovery because of the cryptographic computation that must occur.
• SAODV [31]. Securing AODV proposes a set of extensions that secure the AODV routing packets. Two mechanisms are used to secure the AODV messages: digital signatures to authenticate the non-mutable fields of the messages, and hash chains to secure the hop count information. Since the protocol uses asymmetric cryptography for digital signatures it requires the existence of a key management mechanism that enables a node to acquire and verify the public key of other nodes that participate in the ad hoc network. When a node originates a route request or a route reply message it sets the Max_Hop_Count field to the TimeToLive (TTL) field from the IP header, set a the hash field to random seed value, calculates Top_Hash by hashing random seed Max_Hop_Count times. A node receives a route request or a route reply message, it applies the hash function Max_Hop_Count minus Hop_Count times to the value in the Hash field, and verifies that the resultant value is equal to the value contained in the Top_Hash field. If the intermediate nodes can reply to a route request on behalf of the final destination, the addition of the signature is used to reply to the route quest. Otherwise the route request will be forwarded by the intermediate nodes.
• Securing link-state routing [32]. Secure Link-State Protocol (SLSP) provides a proactive secure link state routing solution for ad hoc networks. SLSP nodes disseminate their link state updates and maintain topological information for the subset of network nodes within R hops, which is termed as their zone. Nodes' public key certificates are broadcasted within their zone using signed public key distribution (PKD) packets. Link state information was broadcasted periodically using Neighbor Location Protocol (NLP). When receiving a Link state update (LSU) packets, nodes verify the attached signature using a public key they have previously cached in the pubic key distribution phase of the protocol and authenticate the hop count by one way hash chains. By securing the neighbour discovery process and using NLP as a way to detect discrepancies between IP and MAC addresses, SLSP offers protection against individual malicious nodes. But SLSP is vulnerable to colluding attackers that fabricate non-existing links between themselves and flood this information to their neighbouring nodes.
Performance Evaluation of Mobility Models for Wireless Ad hoc Networks
The ad hoc mobility models are the continuous time stochastic process, which characterizes the movement of nodes in two-dimensional spaces. According to the movement pattern of each type, each node movement consists of sequence of random length interval, during which a mobile node (MN) moves in constant speed and constant direction. The speed and direction of each node varies according to various mobility models. In the network environment like ad hoc network synthetic mobility models are used because they attempt to realistically represent the behavior of mobile node. In the performance evaluation of handoff algorithm for mobile ad-hoc network, the handoff algorithm should
be tested under realistic conditions and realistic
movements of the mobile user. A mobility model should attempt to mimic the movements of real mobile node, also the changes in speed and direction of node must occur in reasonable time slots. The various synthetic entity mobility models used for Ad-hoc network are as follows.
1) Random Walk Mobility Model: A simple mobility model based on random direction and speeds.
2) Random Waypoint Mobility Model: A model that includes pause times between changes in destination and speed.
3) Random Direction Mobility Model: A model that forces mobile node to travel to the edge of simulation area before changing direction and speed.
4) A Boundless Simulation Area Mobility Model: A Model that converts 2D rectangular simulation area into a torus-shaped simulation area.
5) Gauss Markov Mobility Model: A model that uses one tuning parameter to vary the degree of randomness in mobility pattern.
6) Uniform Mobility Model: Uniform mobility model collects good features of Random walk mobility model, Random waypoint mobility model and Random direction mobility model.
7) Urban Mobility Model: A model that simulates the urban environment. It is basically an enhancement to the common Manhattan mobility model
Distributed Security Scheme for Mobile Ad Hoc Networks
SECURITY IN MANET
In contrast to fixed networks a centralized certification authority is not feasible in ad hoc networks. Distributing the functionality of certification authority over number of nodes
is a possible solution. This can be achieved by creating n shares for a secret key and distributing them to n different node. Key can be generated by combining s shares using threshold cryptography technique.
Mobile ad-hoc networks are highly dynamic; topology changes and link breakage happen quite frequently. Therefore, we need a security solution which is dynamic, too. Any malicious or misbehaving nodes can generate hostile attacks. These types of attacks can seriously damage basic aspects of security, such as integrity, confidentiality and privacy of the node. Current ad-hoc routing protocols are completely insecure. Moreover, existing secure routing mechanisms are either too expensive or have unrealistic requirements. In ad hoc network, security solution should isolate the attackers and compromised nodes in the network. Proactively isolating the attackers ensures that they cannot continue to attack and waste the network resources in future. A security solution should have decreasing overhead over
Attacks against ad-hoc routing protocols can be classified as active or passive. A passive attack does not disrupt the operation of the protocol, but tries to discover valuable information by listening to traffic. An active attack injects arbitrary packets and tries to disrupt the operation of the protocol in order to limit the availability, gain authentication, or attract packets destined to other nodes. In ad hoc network misbehaving node can advertise its availability. Nearby nodes updates its route table with the new route and forward the packet through the misbehaving node. Misbehaving node can modify or even drop the packet. So mobile nodes must be able to verify the trustworthiness of a new neighbor before adding it to the route table. Also it is important to protect the data packets from eavesdropping. Once the cluster member link has established a secured link, they can further exchange symmetric key and encrypt data packet to ensure data confidentially and integrity.
IV. CLUSTER-BASED TOPOLOGY
Clustering is a method by which nodes are placed into groups, called clusters. A cluster head is elected for each cluster. A cluster head maintains a list of the nodes belonging to the same cluster. It also maintains a path to each of these nodes. The path is updated in a proactive manner. Similarly,
a cluster head maintains a list of the gateways to the neighboring clusters. Using the information gathered from the members of the cluster, each cluster head distribute the shares to the cluster members. Each cluster head select a set of gateway nodes. In order to have a secure communication between inter cluster nodes, gateway nodes can act as the trusted member of the corresponding cluster. Through the trusted members secured communication link can be established between two clusters. The cluster head can operate as a trusted certificate authority and it can distribute the certificate share to all cluster members. When a member node fails, at least one of its neighbors reports this node failure to the cluster head. If a cluster head fails, this cluster has to be re-organized and it affects the normal functioning of the network. We propose a novel fully distributed cluster based security mechanism without cluster head.
We assume that self organized mobile networks are formed by a group of nodes having a valid identity (for example communication between the military officials or disaster recovery team). In our design each node is granted temporary admission into the network using an identity verification process. Each node generates a code using the equation (1) and forwards the node ID and code to the neighboring nodes. To verify the identity of the sender, neighboring nodes calculates the hash code using the equation (2). If the generated code and received code are same, it accepts the sender as a valid member and add the sender node ID to set S. (S is the set of all valid neighbors and dynamic clustering algorithm uses set S to create non-overlapping clusters)
time when the network is in good condition without any attacks. By adopting the cluster based security scheme it cause less overhead as the network is in operation and
- y = f (id )
- y = g (id , curi
proactively isolate the attacker.After initial verification all nodes are continuously
monitored by the neighboring nodes and credits are
calculated based on the behavior of the neighbors. Watchdog mechanism is used to monitor the neighboring nodes. A node accumulates its credits as it stays and behaves well in the network. The period of validity is propositional to its credits. Miss-behaving nodes credits are decremented; it will be denied network access when it reaches the minimum threshold level.
A. Probabilistic Clustering Model
It is possible to characterize this type of phenomena to which the poisson distribution is possible. T1, T2, T3 … Tn are the non-overlapping intervals, then the number of nodes entering into the cluster boundary in the interval is independent. There exists a constant q such that the probability of one event (exactly one node enters into the cluster boundary or leaves the cluster boundary) occurs in the interval of length dt is approximated to q*dt. The probability of two or more events will occur during an interval is approximately zero. So the experiment can be called a poisson experiment. For such experiment, if X counts the number of events occurs during any given interval, then it can be shown that X posses a poisson distribution. If the three poisson condition do hold and is X counts the number of events occurs during some specific time interval duration t, the X is poisson distributed with l = qt .
P( X = x) = p( x; l ) = e - l lx / x!
The probability distribution function is
(3)
xxAn edge dominating set
D Ì E
is a split edge dominating
P( X £ x) = ∑ p( x; l ) = ∑ e -l lk / k!
(4)
set if removal of D splits the graphs G1 and G2 into two sub
k =0
k =0
graphs. The split domination number Dn is the cardinality of
E(x) is a parameter that carries information regarding the central tendency of the random phenomenon modeled by X. E(x) is often sufficient to give a partial description in terms of moments of the random variable. A moment generating function of a distribution can be employed to find the
the dominating set.
Cluster creation module forms the non-overlapping clusters based on the valid neighbor set data. Gateway nodes are identified by the cluster maintenance module and all members maintain the list of gateway nodes. Shortest path to
moments of the random phenomenon. Function M X (t )
of the the gateway nodes can be calculated from the local route
table. In addition to the other routing information, it
variable t is defined as the moment of the random
phenomenon X with respect to time t. The cluster topology changes can be represented using the random experiment X. The probability of nodes entering into the cluster boundary and nodes leaving a particular boundary can be calculated from the moment generating function and its mean and variance.
Figure 1 illustrates the protocol stack architecture of our security system. Figure 2 illustrates the composition of our security solution,whichconsistsof fiveinteracted components.
B. Cluster Gateway Node Selection Process
MANETs can be modeled as an undirected graph with weight, G, G= [V, E] V, is the set of the mobile nodes and the E the set of the bidirectional wireless link. G and V are both dynamic set.
. In dynamic network environment asymmetric keys can be used to encrypt/decrypt the data.
C. Cluster Maintenance
Cluster maintenance module proactively maintains the route information of all cluster members. There are four topology changes that requires cluster updation
Node Switches ON:
This will be handled in exactly the same way as cluster formation. This case includes the case when a new node enters into the cluster boundary which is not currently a member of any cluster. A new link (with a node already bound to a cluster) is detected:
This means that an existing node (say, Node A) has moved into the hearing range of another node (Node B). Both nodes A and B will find out the cluster affiliations of each other, update their own routing tables and broadcast this information to their respective cluster members. Note that both these nodes may now become gateway nodes (if both of them are in different clusters).
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