A survey on trust based routing in manet

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  • 1. INTERNATIONAL JOURNAL OF COMPUTER ENGINEERING & International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 – 6367(Print), ISSN 0976 – 6375(Online) Volume 3, Issue 3, October-December (2012), © IAEME TECHNOLOGY (IJCET)ISSN 0976 – 6367(Print)ISSN 0976 – 6375(Online)Volume 3, Issue 3, October - December (2012), pp. 213-222 IJCET© IAEME: www.iaeme.com/ijcet.aspJournal Impact Factor (2012): 3.9580 (Calculated by GISI) ©IAEMEwww.jifactor.com A SURVEY ON TRUST BASED ROUTING IN MANET S.Sridhar P.Chandrasekar Dept. of Computer Applicatons, Dept. of Computer Applications, S.A.Engineering College, S.A.Engineering College, Thiruverkadu P.O., Chennai-77, Thiruverkadu P.O., Chennai-77, ssridharmca@yahoo.co.in mail2chandruu@yahoo.co.in ABSTRACT A mobile ad-hoc network (MANET) is a peer-to-peer wireless network where nodes can communicate with each other without the use of infrastructure such as access points or base stations. Nodes can join and leave the network at anytime and are free to move randomly and organize themselves arbitrarily. In MANETs, each node should not only work for itself, but should be cooperative with other nodes. Working in such environment, MANETs are vulnerable to attacks by malicious and misbehaving nodes that try to compromise the routing protocol functionality. Neighbor based communication without any trust worthiness creates a major vulnerability in security related aspects of this network. In this type of situations, trust value plays a crucial role in all of the network activities. Continuous evaluation of node’s performance and collection of neighbor node’s opinion value about the node are used to calculate the trust relationship of this node with other nodes. Hence a mechanism to formalize trustworthiness among these anonymous nodes is needed to make sure resources are shared among trusted nodes only. Managing trust in a Mobile Ad Hoc Network is challenging when collaboration or cooperation is critical to achieving mission and system goals such as reliability, availability and scalability. This article extensively studies the various trust management approaches and presents an analyses of various trust based protocols which have provided reliability in MANET routing and increases Qos metrics. Keywords MANET, Trust, Misbehaving node, Malicious node, QoS metrics. 1. INTRODUCTION Mobile ad-hoc networks [1], are dynamically configured, multi-hop wireless networks characterized by absence of any infrastructure, dynamic topology and wireless links. MANET composed only of nodes and these nodes do not have fixed infrastructure or any centralized controller such as access point or server to determine the route of the paths. Thus, each node in an ad hoc network has to rely on each other in order to forward packets and there is a need to use a specific cooperation mechanism to forward packet from hop to hop before it reaches a required destination by using routing protocol. 213
  • 2. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 –6367(Print), ISSN 0976 – 6375(Online) Volume 3, Issue 3, October-December (2012), © IAEMEAs nodes may not aware to which nodes it is connected with or which nodes connected to them,therefore access to resources or information can be shared among both trusted and non trusted nodes,unfavorable situation which makes private transactions impossible. The inherent freedom in self-organized mobile ad-hoc networks introduces challenges for trust management; particularly whennodes do not have any prior knowledge of each other. Hence, to assure that access to resources isgiven only to trusted nodes, the trustworthiness among anonymous nodes needs to be formalized.The concept of trust originally derives from social sciences and is defined as the degree of subjectivebelief about the behaviors of a particular entity [2]. Battle field, emergency and disaster environmentsrequire immediate network .formation and trusted route establishment for their communication.MANET is the suitable network for such type of application areas. A trusted system[3] is defined asan entity whose security mechanisms are isolated from and are uncircumventable by unauthorizedusers; the system can be identified, content controlled and secure, and managed by a competentauthority. All the existing MANET protocols simply trust their neighbors and make a route throughthe neighbors. This kind of neighbor based routing is disturbed by intruders and internal attackers ormalicious nodes. In spite of malicious nodes presence in the network, the network must provide itsservices without any problem. This is achieved only by the trust based protocols. Trust establishmentand management between entities (nodes or agents) can be done through a central trusted authority orin a distributed fashion by nodes [4], by a combination of both. Trust is a passive entity in thenetwork.The term ”Trust Management” was introduced by [5] and identified it as a separate component ofsecurity services in networks and clarified that ”Trust management provides a unified approach forspecifying and interpreting security policies, credentials, and relationships.” According to [6, 7], thereare four major properties of Trust and they are, Context Dependence:- The trust relationships are onlymeaningful in the specific contexts. Function of Uncertainty:- Trust is an evaluation of probability ofif an entity will perform the action. Quantitative Values:- Trust can be represented by numeric eithercontinuous or discrete values. Asymmetric Relationship:- Trust is the opinion of one entity for anotherentity. That is, if A trusts B, it is unnecessary to hold that B trusts A.Although many trust management schemes have been proposed to evaluate trust values, no workclearly addresses what should be measured to evaluate network trust. Most trust-based protocols forsecure routing calculated trust values based on the characteristics of nodes behaving properly at thenetwork layer. Trust measurement can be application dependent and will be different based on thedesign goals of proposed schemes [8]. The metrics include overhead (e.g., control packet overheads),throughput, good put, packet dropping rate, and delay. ”Route usage” refers to the number of routesselected particularly when the purpose is for secure routing. ”Trust level” is a recently used systemmetric. Example metrics using the trust level include confidence level of the trust value,trustworthiness, opinion values about other nodes, and trust level per session. In the following sectionwe will discuss about the various trusts based schemes which have deployed routing in mobile ad hocnetwork based on some form of trust.2. ANALYSES OF TRUST MANAGEMENT IN MANETS2.1 Forming Trust Using Direct and Indirect Approach [9]A trust schema for MANET is build to allow two nodes to use trust value computed to determine theaccess control action. The value computed based on formation of trust will either block or allowaccess to be shared between these nodes. The following definitions to be used In the schema.Definition 1: A node that services/information to be shared is known as Servicing Node (SN).Definition 2: A node that request for information/services sharing is known as Request Node (RN).Definition 3: A peer node (PN) is node which is peer to servicing node, which gives recommendationabout Request Node (RN).In this model, 0 represent complete distrust and 1 represent completely trust. An assumption is alsomade where authentication between nodes is already handled by some certification or credentialpassing among nodes when nodes start to collaborate. As such the initial trust value 0.5 is given to RNonce both collaborate. An initial trust value of 0.5 is assumed. After the initial collaboration, during 214
  • 3. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 –6367(Print), ISSN 0976 – 6375(Online) Volume 3, Issue 3, October-December (2012), © IAEMEthe interaction, the new trust value is calculated to determine the access control action. In calculatingthe trust value, The initial trust value plus or minus is combined with the trust value calculated duringthe formation of trust .The value can be increased to >0.5 or be decreased which is <0.5 based oninput gather during interaction or nodes behavior.2.1.1 Direct Approach.There are two cases where direct approach can be used. Case I: RN request to access from SN and SNalready know RN. In this case, SN has the information about RN based on past knowledge viainteraction. However since the new request for resource sharing could be different from the previousor it is a totally new item thus, there is a need to calculate new trust value between these nodes. Eachtime nodes collaborate, the initial trust value is obtained (0.5), and therefore through observation ofSN do on RN, the trust value can be increased (or decreased) based on RN behavior. Both facts aresupported by context specific data such as place/situation and also time. Case II: RN is new to SN andno recommendation about RN from PN. For the second case, when two nodes never met each otherand no recommendation can be gather from peer nodes, therefore SN needs to evaluate RN based onobservation only and SN will have to depend solely on RN’s behavior to calculate the trust value. Thecontext specific data together with time is used to support the evaluation.2.1.2 Indirect ApproachAs for indirect approach, an assumption that there is an existence of peer node (PN) when RN isrequest for resource sharing from SN is made and also that SN has never interacted with RN before isassumed. Hence the trust value calculated will be based on SN’s own observation ((O)SN(c,t)) withpeer recommendation plus/minus the initial trust value . The context data and time will be used as inthe previous formula. Evidences are collected via past knowledge of PN have on RN, reputation ofRN and SN own observation. Reputation used as it can strengthen the recommendation made by PN.Reputation which can be defined as ‘some idea or report of its tendency to fulfill the trust placed in itduring a particular condition; its reputation is created through feedback from individuals who haveformerly interacted with the entity ‘[11]. For example, if RN is a reputable person i.e. well knowntailor who make dresses for many famous people, therefore in this case the tailoring context will bevery good and most importantly can be trusted.2.1.3 Trust MappingThe mapping between the trust value and access control action for resource and information sharing isas follows. The initial trust value 0.5 for collaboration is given to RN each time the nodes collaborate.If the value is less than 0.5 than no access (block) is given otherwise the value will increase graduallyif SN belief that RN is behaving well. To allow flexibility to SN, SN is allowed decide how muchresource can be share with RN during the interaction.Thus a trust schema to form trust among anonymous nodes in the network is framed. The schema isconstructed via direct and indirect approach. The trust schema that is build is used to allow resource tobe shared among trusted nodes. The trust value calculated is then mapping with the access controlprivileges to allow resource/information sharing in MANET.2.2 Hybrid Trust Management Framework (HTMF) [10]Here the focus is on trust management framework, which is intended to cope with misbehaviorproblem of nodes and stimulate nodes to cooperate with each other. However, there are still manyintrinsic problems with the existing trust management frameworks, which remain unsolved, such asfrangibility under possible attacks. To design a robust trust management framework these intrinsicproblems are investigated with the existing frameworks, and propose a hybrid trust managementframework (HTMF) to construct trust environment for MANETs. The proposed HTMF is more robustand reliable than the existing frameworks which face problems like Selective Misbehavior Attack andLocation-dependent AttackStep S1: Update ITF through Direct Information. Each node in the network monitors the behavior ofits neighbors using watchdog mechanism. Step S2: Distribute and process second-hand information.Here, the nodes receiving these information perform deviation test and another check to inhibit badmouthing attack and conflicting behavior attack. Step S3: Evaluate trust value and confidence value.In this step, these two values are formed based on ITF obtained through steps S1 and S2. Step S4: 215
  • 4. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 –6367(Print), ISSN 0976 – 6375(Online) Volume 3, Issue 3, October-December (2012), © IAEMEEvaluate trustworthiness. Since two parameters are difficult for comparison two parameters formed inS3, namely trust value and confidence value, are combined into a whole trust metric, trustworthiness.This HTMF holds objective characteristic by which trust for a node is evaluated based on not onlydirect observations but second-hand information. It makes HTMF robust under selective misbehaviorattack and location-dependent attack in contrast to the trust establishment framework.2.3 AMLET: Adaptive Multi Level Trust Framework [11]Adaptive Multi Level Trust model called AMLeT is proposed using two complementary trust levels.AMLeT calculates trust in one level of hard or soft and updates calculated trust considering networkfield, modifications of context and situations with the passing of the time. AMLeT is extensible fordifferent fields of network, applications and situations. AMLeT based AODV routing was improved.and the results indicated overall improvement in the network performance without imposingparticular overhead time in network operations.2.3.1 Trust CriteriaThree new criteria introduced to improve more accurate trust model for MANETs. The proposedcriteria can lead to develop an adaptive trust model. The criteria are introduced in the following:Process time: The first one is elapsed time to evaluate and deploy trust value to target node andtransmit the value to the others. It is obvious that this factor depends on the amount of process andbeing early or late (proactive or reactive). Optimism or pessimism: This factor firmly depends onsecurity level of the application. The context and situation of the application have an important effecton the default trust value of an entity. Thus, the initial trust values to others are supposed to be low.Trust slope: This criterion depends on two factors. First, the elapsed time in which the trust reaches tohighest value. That refers to the manner of the trust function to increase the trust value observing thepositive evidences. Second, the required subsequence of negative behaviors that cause the trust valuebecomes lowest level. That means the manner of the trust function to decrease the trust valueobserving negative evidences.2.3.2 Hard trust and Soft trustUsing both the criteria, defined by the others and the criteria proposed above, two levels of trustwhich take into account these criteria differently are stated below. Hard trust is a level of trust that themanner of its trust function is slow in rising and sharp in falling. In Hard trust, trust function increasestrust value gradually, but decreases it keenly. This level of trust is well suited to the networkapplications which require operating in a high security mode. The transmitting data in this networks isworthy to insider and outsider entities. So there are many incentives to express malicious behaviors.Soft trust is a level of trust that the manner of trust function is sharp in rising and slow in falling. Softtrust is appropriate for network applications with stable conditions. The proportion of needed securityto the amount of the transmitting data is low. Therefore, there are not many incentives to expressmalicious behaviors in these networks. Continuity of life in these network applications is moreimportant than security. It means that network will continue to operate correctly despite of light injuryin some data and negative behaviors of some nodes.Hardness parameter is a numeric parameter that indicates required security level of a MANETapplication in an instant of network life. This parameter is computed regarding type of MANETapplication, optimism or pessimism, and trust slope criteria. Considering hardness parameter in everyinteraction, trustworthiness will be estimated using the computed Hard trust and Soft trust. Thereforein this trust model, the required level of security for the application and dynamic situations areconsidered to evaluate trustworthiness in each interaction between nodes. In Figure 3, a schematicview of AMLeT framework is presented. This framework consists of six operating units to evaluatetrust adaptively to situation and type of the network, using two defined level of trust2.3.3 An AMLeT based routingAODV is one of the most important reactive routing protocols in MANETs. This improvement isdone by integrating AMLeT modules into AODV agent in order to boost some security and efficiencyfactors. Threshold value for trustworthiness is 0.5 which determines the border of trustworthiness anduntrustworthiness. After packet forwarding, the AODV agents evaluate the behavior of their adjacent 216
  • 5. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 –6367(Print), ISSN 0976 – 6375(Online) Volume 3, Issue 3, October-December (2012), © IAEMEnodes. Hardness parameter is determined base on N recent interactions. Finally, these values arepassed to mixture trust function to calculate the trustworthiness of the target node. Trustworthiness ofeach node is used in routing process to punish distrusted nodes and to improve routing efficiency byisolating established routs from them and having more trusted routes. Thus two complementary levelsof trust have been introduced for mobile ad-hoc networks naming Hard trust and Soft trust. Theselevels can be foundation to develop trust models for each application. Each of defined trust levels isdesirable and usable for the applications with same security requirements. In fact, AMLeT adaptsitself to context and situations changes of network. Functionality and feasibility of AMLeT wereproved by AMLeT based AODV routing.2.3.4 An AMLeT based routingAODV is one of the most important reactive routing protocols in MANETs. This improvement isdone by integrating AMLeT modules into AODV agent in order to boost some security and efficiencyfactors. Threshold value for trustworthiness is 0.5 which determines the border of trustworthiness anduntrustworthiness. After packet forwarding, the AODV agents evaluate the behavior of their adjacentnodes. Hardness parameter is determined base on N recent interactions. Finally, these values arepassed to mixture trust function to calculate the trustworthiness of the target node. Trustworthiness ofeach node is used in routing process to punish distrusted nodes and to improve routing efficiency byisolating established routs from them and having more trusted routes. Thus two complementary levelsof trust have been introduced for mobile ad-hoc networks naming Hard trust and Soft trust. Theselevels can be foundation to develop trust models for each application. Each of defined trust levels isdesirable and usable for the applications with same security requirements. In fact, AMLeT adaptsitself to context and situations changes of network. Functionality and feasibility of AMLeT wereproved by AMLeT based AODV routing.2.4 Trust Based Security Approach Using Trust Counter [12]A trust based packet forwarding scheme is designed for detecting and isolating the malicious nodesusing the routing layer information. It uses trust values to favor packet forwarding by maintaining atrust counter for each node. A node will be punished or rewarded by decreasing or increasing the trustcounter. If the trust counter value falls below a trust threshold, the corresponding intermediate node ismarked as malicious.In this approach, by dynamically calculating the nodes trust counter values, the source node can beable to select the more trusted routes rather than selecting the shorter routes. Changes are done to theAODV routing protocol. An additional data structure called Neighbors Trust Counter Table (NI T) ismaintained by each network node. The routing process can be summarized into the following steps: 1)Discovery of routes: it is just like the route discovery in DSR. Suppose A starts this process tocommunicate with D. At the end, A collects all the available routes to D; 2) Validation of routes:Node A check the trust values of the intermediate nodes along the path. Assuming node Bs trust valueis missing in A s trust table or its trust values is below a certain threshold, put B into a set X. 3)During the transmission, node A updates its trust table based on the observations. When somemalicious behavior is found, A will discard this path and find another candidate path or restart a newdiscovery. 4) Compute trust values for every node in X based on the trust graph. 5) Among all paths,A chooses the one with the max ( in= 1 pi) where n is the number of nodes along with path. A trust based security protocol which attains confidentiality and authentication of packets in bothrouting and link layers of MANETs is developed. It uses trust values to favor packet forwarding bymaintaining a trust counter for each node. The perfect security solution is hard to reach. But theaverage security level (for a node) can be achieved as expectation based on accumulated knowledgeand as well as the trust relationship built and adjusted.2.5 Trust Based Secure Routing Using NTC And RTC [13]Continuous evaluation of node’s performance and collection of neighbor node’s opinion value aboutthe node are used to calculate the trust relationship of this node between source and estimations 217
  • 6. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 –6367(Print), ISSN 0976 – 6375(Online) Volume 3, Issue 3, October-December (2012), © IAEMEwithout any intruders or malicious nodes can be established with the proposed trust based routingprotocol that equally concentrates both in node trust and route trust.2.5.1 Node Trust Calculation ProcessEach node has opinion about other node’s (neighbor) trustworthiness. Node X has an opinion abouttrustworthiness of one of its neighbor node Y based on Y’s previous and current behaviors. All thenodes in such environment already maintain Routing Table. Additionally added Neighbor Tableshould be maintaining in all the nodes for keep tracks the dynamically changing neighbor list and itscorresponding node trust value.Node trust is calculated by the collective opinion of node’s neighbors.The resultant trust value is placed in Trust Value field of Neighbor Table. The node trust is computedbased upon the information that one node can collect about the other nodes.2.5.2 Route Trust Calculation ProcessRoute trust is computed by every node for each route in its routing table. Existing Routing Tableextended with one more field; Route Trust. In this approach, source node selects the route which ishaving the highest Route Trust value. Route Trust field of every Routing Table entry is updated atsome regular interval. In this method, only one additional field is enough to monitor the route trustworthiness. Destination node in each entry originates R_ACK message packet to node which one ismaintaining this routing Table. R_ACK is the modified version of RREP_ACK message packet. Eachroute already having the entry for number of packets sent to the corresponding destination. Usuallydestination node originates R_ACK message packets. This packet moves backward direction from thedestination. Node which one is receiving R_ACK packet uses the entry Number of Packets Receivedfor route trust calculation.2.5.3 Route Establishment ProcessSource initiates route establishment process by broadcasting RREQ message to all of its neighbors.Each node maintains two main table; Route Table and Neighbor Table. Each node updates itsNeighbor Table by broadcasting HELLO packets in the regular interval. Neighbor Table consists oftwo fields; Neighbor_ ID and Trust Value. Another table in every node is route Table. It maintains theroute detail information like Destination IP Address, Destination Sequence Number. ValidDestination Sequence Number, Next Hop, Hop Count and Route Trust etc. for all the routes those arevalid from this node. At the time of route establishment process or packet forwarding process, thistable is updated. Neighbor nodes check this routing table whether they are having any route to thedesired destination or not. If it exists then nodes can sent a RREP message to source in the backwardpath. Source waits for more than one RREP from its neighbors. In this method, Route Trust value ofthe RREP message plays a major role in RREP selection process. Based on the highest Route Trustlevel, the RREP is selected for further route establishment.Proposed modifications are in acceptable limit. With this minimum overhead, the malicious nodes areeliminated as well as a best trusted route between source and Destination is established and also itcreates a secure communication in this environment without any internal attackers.2.6 TBAODV - Trust Based AODV [14]The performance of Ad-hoc On Demand Vector protocol is modified by including the source routeaccumulation feature. As low transmission power of each ad-hoc node limits its communicationrange, the nodes must assist and trust each other in forwarding packets from one node to another.However, this implied trust relationship can be threatened by malicious nodes that may fabricate,modify or disrupt the orderly exchange of packets. Security demands that all packets be authenticatedbefore being used. A particularly hard problem is to provide efficient broadcast authentication, whichis important mechanism for MANET. Here, a routing algorithm is proposed which adds a field inrequest packet which stores trust value indicating node trust on neighbor. Based on level of trustfactor, the routing information will be transmitted depending upon highest trust value among all. Thisnot only saves the node’s power by avoiding unnecessary transmitting control information but also interms of bandwidth (channel utilization), which is very important in case of MANET. Here, trustedpath is used irrespective of shortest or longest path which can be used for communication in thenetwork. Route trust value is calculated for the complete reply path which can be utilized by sourcenode for next forthcoming communication in the network. 218
  • 7. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 –6367(Print), ISSN 0976 – 6375(Online) Volume 3, Issue 3, October-December (2012), © IAEME Algorithm for different functions used in packet transmission and reception routine as follows: Step1:-Initially trust value 100 is assigned to all nodes in the network using assign trust ( ) function. Step2:- Trust value are printed using Printtrust ( ) function. Step 3:- Source node broadcast request to allits neighbouring node using Send_Request( ) function.In this function hop count is initialized.Schedular class is invoked to run the simulation. Step 4:- Neighbouring node receive the request thenit will check whether it is destination or not.If it is Destination then it will Send_Reply( ) functionotherwise forward request to its neighbouring node. This will check in Receive_Request( ) function.Step 5:- After confirming that it is not destination, it will further forward request to all itsneighbouring node using Forward_Request( ) function.Hopcount is increased at each node. Step 6:-Ifit is destination then it will send reply using Send_Reply( ) function. Trust value 200 is assigned to allnodes in the path from destination to source node. Now, Source becomes destination for the currentnode. Step 7:-After receiving the reply then the decision will take whether the index node isdestination or not using Receive_Reply( ) function. If it is not destination then it will forward reply.In TBAODV an extra field is created in the route request format. This trust value is updated on everysuccessful communication. The forthcoming communication is based on the route selection valuecalculated for each RREQ path. This route selection value is used to select most trusted path ratherthan selecting shortest or longest path. This significantly improves the trust factor on the neighboringnodes in the network. Thus the trust based routing protocol proposed here improves the security leveland also prevent malicious node attack in the network.2.7 Trusted And Shortest Path Selection Using R-AODV [15]A security enhanced AODV routing protocol called R-AODV (Reliant Ad hoc On-demand DistanceVector Routing) is defined. The implementation of this work is done by modifying a trust mechanismknown as direct and recommendations trust model and then incorporating it inside AODV which willallow AODV to not just find the shortest path, but instead to find a short path that can be trusted. Thisenhances security by ensuring that data does not go through malicious nodes that have been known tomisbehave. R-AODV does provide a more reliable data transfer compared to the normal AODV ifthere are malicious nodes in the MANET.2.7.1 Reliant On-Demand Distance Vector Routing Protocol(R-AODV)AODV can be modified to select better path (best path (Bp)) during the route discovery cycle basedon the trust and number of hops (trusted and shortest). When the route request and route reply (R-RREQ and R-RREP) messages in Reliant R-AODV are generated or forwarded by the nodes in thenetwork, each node appends its own trust to the trust accumulator (trust summation accumulator S[t])on these route discovery messages. Each node also updates its routing table with all the informationcontained in the control messages. As the R-RREQ messages are broadcast, each intermediate nodethat does not have a route to the destination forwards the R-RREQ packet after appending its trust tothe trust accumulator in the packet. Hence, at any point, the R-RREQ packet contains a list of all thenodes visited with their trust value added to trust summation accumulator S[t]. Whenever a nodereceives a R-RREQ packet, it will check the updates of the route to the source node. It then checks forbetter path (best path (Bp)) for intermediate nodes. The hop count included in the request message. Anew entry is made in the routing table for any of the intermediate nodes and assigns full trust to them,if one did not already exist. If a route entry for a node does exist, and if best path (Bp) to any of theintermediate nodes is greater than the previously known best path (Bp) to that node, the routing tableentry is updated for that node and assigns new trust value. New trust value will be updated in routingtable. The entry is updated by retaining the previously known sequence number for that node.2.7.2 Route Discovery in R-AODVThe goal of this protocol is for source node to select the secure route with less hop count to adestination node. The source node, S, broadcasts a route discovery message (R-RREQ) to itsneighbours which contains: S broadcasts R-RREQ <Source_Addr, Source_Seq#, Broadcast_ID,Dest_Addr, Dest_Seq#, Hop_Count, S[t], Bp> As RREQ messages in AODV, for R-AODV, when anode receives R-RREQ message, it sets up a reverse path back to the source by recording theneighbour from which it received the R-RREQ. Meanwhile, when the node receives the R-RREQ, itwill check whether it is the destination or not, if so, it will updates the routing table for that node andgenerate R-RREP. But if the receiver node was intermediate node, it attaches the trust value in its 219
  • 8. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 –6367(Print), ISSN 0976 – 6375(Online) Volume 3, Issue 3, October-December (2012), © IAEMErouting table to the trust summation accumulator S[t] in the message. Upon receiving the message, anode verifies the Best path in the routing table with the new best path value attached in the message, ifthe new best path greater than the one in the routing table, the node then update the routing table2.7.3 Route Reply in R_AODVAfter receiving the R-RREQ, the destination node creates a route reply message (R-RREP), signs itand unicasts the reply massage back to the source over the reverse path. The destination node, D,creates the R-RREP, and sends it back to its neighbour. Route Reply message contains: D unicasts R-RREP: <Source_Addr, Dest_Addr, Dest_Seq#, Hop_Count, Lifetime, S[t], Bp> With the inclusion oftrust mechanism.It is expected that using R-AODV would result in a higher percentage of successful data delivery ascompared to AODV. However, it is also expected that due to the extra processing done and thepossibility that the packets may take a longer route, it is also expected that the normalized routingload and end-to-end delay would increase. The use of R-AODV does provide a higher percentage ofsuccessful data delivery. It has also shown that the impact to normalized routing load and end-to-enddelay is very minimal.2.8 Reputation-Based Trust Model [16]The main objective here is to highlight critical issues that impinge upon trust management and topropose a reputation based approach for establishing trust that dynamically assesses thetrustworthiness of the participating nodes in the MANET environment.2.8.1 Critical Issues in Trusted SystemsInitially certain security issues are discussed here. Identify a set attributes necessary for a mobile nodeto support critical infrastructure related activities in a MANET. To be deemed as trustworthy, a nodemust make a reasonable effort to perform its generic functions and duties in the network in adependable manner, broadly categorized under headings of Routing/Forwarding, Quality of Service,and Security.The routing and forwarding functions are governed by routing protocols. A robust routing protocolreduces packet loss rates, eliminates the possibility of having frequent route failures, and is able tocope quickly against topological changes. Quality of Service (QoS) is the ability of the underlyingnetwork to provide preferential treatment to certain network traffic flows over others. In SecurityRelated Functions Trust on a system is enhanced if the system has security mechanisms to safeguardits assets and actions. However, trust can also be established in a situation where “trustee will act inthe interests of a trustor without a guarantee” and in the absence of security. What this implies is thatif an entity is convinced or if enough assurance evidence exists that a target has acted in a consistentand predictable manner over an extended period of time and its actions adhere to a moral code or astandard as prescribed by a high level management policy then this target entity is perceived to betrustworthy. Certainly the presence of security services in the system such as confidentiality, integrityand access control and the ability to enforce them using a policy is likely to enhance trust on thissystem.The design principles of the trust model and then proposes trusted-platform architecture to support itare discussed below. The process of computing trust is based on the reputation of mobile nodes andindependent of the underlying security, routing and QoS protocols, mechanisms, and algorithms beingused.2.8.2 Design Principles of Reputation-Based Trust ModelThe framework is built upon the following principles; Individualistic Model: This frameworkprovides a means for node to build its trust on a target independent of other nodes. It may also use therecommendation of a trustworthy peer. Notion of reputation: The sense of trust builds upon the notionof reputation. The reputation of a target node is determined on the basis of first hand information thatresults through direct experience of interacting with that node, or through observation, or throughrecommendation / references of peers. Trust is context dependent: This means that entities can betrusted for only certain functions. In this model, trust is also a function of reputation that is 220
  • 9. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 –6367(Print), ISSN 0976 – 6375(Online) Volume 3, Issue 3, October-December (2012), © IAEMEcontinuously changing with each new interaction. It is also time sensitive meaning an entity can onlybe trusted for a certain period time. Trust is reflexive, asymmetrical, non-transitive: There is areflexive need to be able to protect one’s own resources. This model also perceives trust between twonodes as an instance of asymmetrical reciprocity. Also the non transitive property of trust ispreserved. Trust depends on device capability: Each participating entity in a MANET must be awareof the device capability (hardware, OS, trusted platform) of every other node or at least itsneighboring nodes.2.8.3 Protocol Stack and Trusted PlatformThe trust framework proposed is supported by a trusted architecture and a protocol stack. The trustedplatform (TP) acts as an enforcement point of various trustworthy services in the node. It provides atamper resistant hardware supported by a Trusted Platform Module (TPM) that provides someprimitive cryptographic functions such as random number generation, RSA key generation and has amechanism for protecting data by never releasing the root key outside the confines of TPM.Thus a decentralized framework is presented for building a trust model for MANETs. The model oftrust is independent of underlying cryptographic schemes and also takes into account the hardwareconstraints of the devices. In this scheme the notion of trust is bound to a function the node performsin the network rather than to the node itself.3. CONCLUSIONThe study covers a hand full of works related to trust management in MANETS. The routing protocolimproved with enhancements and new strategies implemented to bring in reliability in MANETrouting. The objective of all works listed here focuses on providing trustworthy routing in MANET,eliminating the misbehaving nodes and the nodes which bring down the performance of the network.It also focuses to improve the performance of the network by increasing the Qos metrics. Based on theobservations the future work can be coined in such a way that the routing in MANET should beimplemented with a trust scheme which guarantees trustworthy routing, scheme to identify and isolatemisbehaving node and also to improve the QOS metrics.4. REFERENCES[1] Corson, S. and Macker, J. 1999 Mobile Ad Hoc Networking (MANET):Routing Protocol Performance Issues and Evaluation Considerations. In RFC 2501.[2] Cook, K. S. (editor), Trust in Society, vol. 2, Feb. 2003, Russell Sage Foundation Series on Trust, New York.[3] IBM Corporation. Enterprise Wide Security Architecture and Solutions Presentation Guide. 1st Edition, November 1995.[4] Rahman. A. and Hailes, S. 1997 A Distributed Trust Model. New Security Paradigms Workshop 1997 ACM.[5] Blaze, M., Feigenbaum, J. and Lacy, Z. 1996 Decentralized Trust Management. In Proceedings of the IEEE Symposium on Security and Privacy.[6] Farooq Anjum, Dhanant Subhadrabandhu and Saswati Sarkar, 2003 Signature based Intrusion Detection for Wireless Ad-Hoc Networks: A Comparative study of various routing protocols. In the of proceedings of IEEE 58th Conference on Vehicular Technology.[7] Marc Branchaud, Scott Flinn, x Trust: A Scalable Trust Management Infrastructure.[8] Jin-Hee Cho, Ananthram Swami, and Ing-Ray Chen, A. 2011 Survey on Trust Management for Mobile Ad Hoc Networks. In IEEE communications surveys & tutorials. 221
  • 10. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 –6367(Print), ISSN 0976 – 6375(Online) Volume 3, Issue 3, October-December (2012), © IAEME[9] Asmidar Abu Bakar, Roslan Ismail, Jamilin Jais, 2009 Forming Trust in Mobile Ad -Hoc Network. In IEEE International Conference on Communications and Mobile Computing.[10] Ruidong Li , Jie Li , Peng Liu, and Jien Kato, 2009 A Novel Hybrid Trust Management Framework for MANETs. In IEEE 29th IEEE International Conference on Distributed Computing Systems Workshops.[11] Hamed Samavati, Behrouz Tork Ladani, Hossein Moodi, 2011 AMLeT: Adaptive Multi Level Trust framework for MANETs. In the International symposium on CNDS.[12] Dr. Sanjeev sharma, Renu mishra, and Inderpreet kaur, 2010 New trust based security approach for ad-hoc networks. In IEEE.[13] Menaka Pushpa, A., 2009 Trust Based Secure Routing in AODV Routing Protocol. In IEEE.[14] Mangrulkar, R. S., and Dr. Mohammad Atique. 2010 Trust Based Secured Adhoc on Demand Distance Vector Routing Protocol for Mobile Adhoc Network. In IEEE.[15] Hothefa Sh.Jassim, Salman Yussof, Tiong Sieh Kiong, Koh, Roslan Ismail, S. P. 2009 A Routing Protocol based on Trusted and shortest Path Selection for Mobile Ad hoc Network. In the proceedings of 9th Malaysia International Conference on Communications, IEEE.[16] Rajan Shankaran, Vijay Varadharajan, Mehmet Orgun, A., and Michael Hitchens. 2009 Critical Issues in Trust Management for Mobile Ad-Hoc Networks. In IEEE IRI , Las Vegas, Nevada, USA. 222