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  1. 1. ISSN: 2278 – 1323 International Journal of Advanced Research in Computer Engineering & Technology Volume 1, Issue 5, July 2012SECURE MULTICAST COMMUNICATION USING GROUP BASED MULTICAST HIERARCHY R. Varalakshmi#1, Dr. V. Rhymend Uthariaraj*2 # Teaching Research Associate – Department of Mathematics, Anna University, Chennai, India * Professor and Director, Ramanujan Computing Centre Anna University, Chennai, India Abstract— Secure multicast communication is a significant members and used to encrypt the transmitted requirement in emerging applications in adhoc environments like military or public emergency network applications. Membership content. In order to prevent the joined members dynamism is a major challenge in providing complete security in from reading previous content and the left member such networks. This paper proposes a efficient Group Based from reading the further content, TEK must be Multicast Hierarchy (GBMH) algorithm for secret multicast communication, in which source nodes used the Secure Ad hoc refreshed after the membership is changed. An easy On Demand Distance Vector (SAODV) protocol is an extension way is to allow the key server to share a unique key of the AODV protocol. The Secure AODV scheme is based on the encryption key(KEK) with every member. When assumption that each node possesses certified public keys of all network nodes. The SAODV protocol collects its 1 hop the membership is changes, the key server uses the neighbours to form group. This protocol sends acknowledgement individual KEK of every member to encrypt the for each transmission in order to reduce the retransmission. new TEK. This is an inefficient method because the Membership dynamism was overcome by electing local controllers and with periodic updates of node join and leave cost of TEK updates grows linearly with the group information using multicast hierarchy. The performance is size. Therefore, the key changing process becomes studied in terms of average end to end delay and fault tolerance a critical problem in multicast key management. in multicast transmission. Efficient key management protocols should be taken into consideration for security requirements. Keywords— Secure Multicast Communication, Adhoc environments, Membership Dynamism, GBMH, SAODV Security requirements: I. INTRODUCTION 1. Forward secrecy: In this case, users left the Many applications like pay-per–view, distribution group should not have access to any future key. of digital media etc., require secure multicast This ensures that a member cannot decrypt data services in order to restrict group membership and after it leaves the group. enforce accountability of group members. A major 2. Backward secrecy: A new user who joins the issue associated with the deployment of secure session should not have access to any old key. This multicast delivery services is the scalability of the ensures that a member cannot decrypt data sent key distribution scheme. This is particularly true before it joins the group. with regard to the handling of group membership 3. Non-group confidentiality: Here users that are changes, such as membership departures and/or never part of the group should not have access to expulsions, which necessitate the distribution of a any key that can decrypt any multicast data sent to new session key to all the remaining group the group. members. As the frequency of group membership 4. Collusion freedom: Any set of fraudulent users change increases, it becomes necessary to reduce should not be able to deduce the currently used key. the cost of key distribution operations. A common method for secure multicast communications is to The process of updating the keys and distributing use a symmetric key called traffic encryption them to the group members is called rekeying key(TEK), which is shared by all legitimate group operation. A critical problem with any rekey 231 All Rights Reserved © 2012 IJARCET
  2. 2. ISSN: 2278 – 1323 International Journal of Advanced Research in Computer Engineering & Technology Volume 1, Issue 5, July 2012technique is scalability [6]. The rekey process which does not need to perform node splitting aftershould be done after each membership change, and the member joining but it has better than averageif the membership changes are frequent, key rekeying performance than a B-tree.management will require a large number of keyexchanges per unit time in order to maintain both Key management approaches can be classifiedforward and backward secrecies. More frequent into three classes: centralized, distributed ormembership dynamism causes node failure, link decentralized. Distributed key agreement protocolsfailure, power failure leads to time delay in do not rely on a group leader which has anmulticast transmission. To overcome these advantage over those with a group leader because,problems, several approaches propose a multicast without a leader, all members are treated equallygroup clustering. [7, 8, 9]. Grouping is dividing theand if one or more members fail to complete themulticast group into several sub-groups. Local protocol, it will not affect the whole group. In thecontroller (LC) manages each subgroup, which is protocols with a group leader, a leader failure isresponsible for local key management within the fatal for creating the group key and the operationcluster. Thus, after Join or Leave procedures, only has to be restarted from scratch. The 1-affects-nmembers within the concerned cluster are affected phenomenon is not considered because inby rekeying process, and the local dynamics of a distributed protocols all the members arecluster does not affect the other clusters of the contributors in the creation of the group key andgroup and hence it overcomes 1-affects-n hence all of them should commit to the new key[21,22,23,24] phenomenon. Moreover, few whenever a membership change occurs in the group.solutions for multicast clustering such as dynamic The decentralized approach divides the multicastclustering did consider the issue of average end to group into subgroups or clusters, each sub-group isend delay to achieve an efficient key distribution managed by a LC (Local Controller) responsible forprocess, whereas delay in transmission constitutes security management of members and its subgroup.main issue in ad hoc environments. Two kinds of decentralized protocols are distinguished as static clustering and dynamic II. RELATED WORK clustering. In Static clustering approach, the In order to reduce the rekeying overhead, the key multicast group is initially divided into severaltree architecture has been widely used in multicast subgroups. Each subgroup shares a local sessioncommunications. First, a logical key hierarchy key managed by(LKH) tree approach [16,17] has been proposed toreduce the computational and transmitted cost from LC. Example: IOLUS [7] belongs to theO(n) to O(log n) in the rekeying process, where n is categories, which are more scalable than centralizedthe number of group members. Then several protocol. Dynamic clustering approach aims toimprovements are proposed. Lie et al. [18] solve the ―1 affect n‖ phenomenon. This approachproposed a periodic batch rekeying algorithm to starts a multicast session with centralized keysolve synchronization and inefficiency problems. management and divides the group dynamically.Sherman and McGrew [15] proposed a one-way Example: AKMP [8], SAKM [9] belong to thisfunction tree (OFT) to reduce the size of the approach and are dedicated to wired networks.rekeying message from 2(logd n) to only (logd n). Enhanced BAAL [10] and OMCT [11, 12] proposeHowever, the communication cost will be greater dynamic clustering scheme for multicast keythan (logd n) as soon as the key tree is out of distribution in adhoc networks.balance. Recently, the approaches for keeping thetree architecture balance have been proposed. Goshi OMCT (Optimized Multicast Cluster Tree) is aand ladner [18,19] solved the unbalance problem dynamic clustering scheme for multicast keybased on 2-3 trees and have the best performance distribution dedicated to operate in ad hoc networks.with the degree-3 key trees. Lu[20] proposed the This scheme optimizes energy consumption andnon-split balancing high-order (NSBHO) tree, 232 All Rights Reserved © 2012 IJARCET
  3. 3. ISSN: 2278 – 1323 International Journal of Advanced Research in Computer Engineering & Technology Volume 1, Issue 5, July 2012latency for key delivery. Its main idea is to elect the when the signature is verified. When the nodelocal controllers of the created clusters. OMCT reaches the destination, the node signs the ROUTEneeds the geographical location information of all REPLY with its private key and sends it back. Thegroup members in the construction of the key intermediate nodes again verify the signature .Thedistribution tree. signature of the sender is again stored with the along with the route entry. Once the clusters are created within the multicastgroup, the new LC becomes responsible for the A. Featureslocal key management and distribution to their localmembers, and also for the maintenance of thestrongly correlated cluster property. The election of i. Ownership of certified public keys enableslocal controllers is done according to the intermediate enable intermediate nodes tolocalization and GPS (Global Positioning System) authenticate all in-transit routing packets.information of the group members, which does not ii. The protocol operates mainly by using the newreflect the true connectivity between nodes. Based extension message with the SAODV protocol.on the literature reviewed, OMCT is the efficient iii. The SAODV can be used to protect the routedynamic clustering approach for secure multicast discovery mechanism of the AODV by providingdistribution in mobile adhoc networks. To enhance security features like integrity, authentication andits efficiency, it is necessary to overcome the nonrepudiation.criteria, as OMCT needs geographical locationinformation in the construction of key distribution SAODV have multicast connectivity betweentree by reflecting true connectivity between nodes. nodes. It sends acknowledgement for eachIt does not acknowledge the transmission and transmission in order to reduce the retransmission.results in delay in multicast transmission. The LCs are elected easily with periodic updates of node join and leave information using multicast Several different protocols have been proposed hierarchy. This overcomes the issues of end to endfor ad-hoc routing. The proposal of this paper is to delay in multicast transmission and also toleratespresent an efficient Group Based Multicast the fault that occurs due to node failure. TheHierarchy (GBMH) using Multicast version of GBMH algorithm is simulated with networkSAODV for secure multicast key distribution. simulator NS-allinone-2.33 and the performance is studied in terms of average end to end delay and III. SAODV OPERATION fault tolerance in multicast transmission. The originator of the routing control packet IV. EFFICIENT GBMH WITH SAODVappends its RSA signature and the last element of ahash chain to the routing packets. A packet The proposed approach is to achieve securetransverse the network, intermediate nodes multicast communication for adhoc networks. Thiscryptographically authenticates the signature and approach uses Multicast version of SAODV routingthe hash value. The intermediate nodes generate the protocol to maintain routing table periodically. Itkth element of the hash chain, with k being the forms multicast hierarchy among the groupnumber of transverse hops, and place it in packet. members. Each node can determine their present physical location. It quickly adopts to the topology The SAODV protocol gives two alternatives for changes. It is used to discover alternate route forROUTE REQUEST and ROUTE REPLY messages. failure of existing route. It also sendsIn the first case when a ROUTE REQUEST is sent, acknowledgement for each transmission in order tothe sender creates a signature and appends it to reduce the retransmission. Thus the approach ofpacket. Intermediate nodes authenticate the GBMH using SAODV tends to have multicastsignature before creating or updating the reverse connectivity between the nodes.route to the host. The reverse rout is stored only 233 All Rights Reserved © 2012 IJARCET
  4. 4. ISSN: 2278 – 1323 International Journal of Advanced Research in Computer Engineering & Technology Volume 1, Issue 5, July 2012 The approach of Efficient GBMH with SAODV group 0), encrypt with the respective public keys.is described in five phases with specific notations Each local controller should join this group. The local controllers decrypt the message, extract the Phase 1: Authentication: For each node, assign TEK, re-encrypt it with their respective group keyscertificate key to verify its node identity. Each node and send it to all their local members.has address, node address and certificate key. TEK DistributionCertificate key and its IP address encrypt to form a For all mgik ,Gk → mg ik:{TEK, Num_Seq,public key. Thus, each node is authenticated based KEK_GSG ik, IDG, IDGSG, Pub_G,(GBID_CG)on broadcast request and reply. Pri_G }Pub_ mg ik Node Authentication and Access Control Phase 5: Node mobility: For frequent node mg ik → LCik: Join_Request, Pub_mgik mobility, a new member may join a group or an LCik → mgik : Join_Request existing member may leave a group. To ensure mgik→ LCik: Join_Reply, Pub_ mg secure multicast communication, both forward andik ,{GBID_}Pri_mg ik backward secrecy has to be maintained. Phase 2: Group Head Election: Initially the list Forward Secrecy: When a node leaves theof Local Controllers(LCs) contains only the source multicast group, it cannot decrypt the future data.Group Controller (GC). Then, GC collects all its 1 The leave operation is in two caseshop neighbours by SAODV routing protocol. Elect I. When an ordinary node leaves, it gives lessLCs which are group members and which have effect in multicast transmission. The leavechild group members ( the LC belongs to the operation of an ordinary node is specified asunicast path between the source and the child group follows:members). Verify for each one if it a group memberand if it has child group members then add the LC Leave Procedureto the list of LCs. Thus, LCs are selected as groupheads for its corresponding group members. mg ik : outgoing member leaving a group For mg ik : Local member, Phase 3: Group Formation: All the members mg ik < > mg ik _outgoingreachable by this new LC will form a new group. If LC ik → mg ik:{IDLC, KEK_GSG ik }Pub_ mg ikgroup members that exist and do not belong to the II. When a local controller leaves, it leads toformed group then choose the nodes that have the clusterization. It first sends the leave notification tomaximum reachability to the other nodes in one hop the group controller and then all the members of thefrom the remaining members. This reachability current LCs are merged with the other group basedinformation is collected through the SAODV on the reachability information obtained by therouting protocol. Thus, nodes are selected as local SAODV routing protocol.controllers for the remaining group members andforms new group. Leave Notification Phase 4: Secure Multicast Communication: LC ik → GLC:{ID_ LC ik }KEK_GLCThe source encrypts multicast data with the TEK, For all j< > i, GC k → LC ik :{ID_GC,and then sends it to all the members of the group new_KEK_GLC} Pub_CL jkfollowing the multicast hierarchy. The TEK Mergedistribution is achieved in parallel, according to the For all mg ik, LC ik : {ID_group, LL_LCfollowing steps. Initially, the entire group members ik }KEK_GSGikreceive from the source by unicast the session keyKEKgsg-0(key encryption key of the group sub- 234 All Rights Reserved © 2012 IJARCET
  5. 5. ISSN: 2278 – 1323 International Journal of Advanced Research in Computer Engineering & Technology Volume 1, Issue 5, July 2012 Backward Secrecy: When a new node joins themulticast group, it cannot decrypt the pastencrypted data. Each new node is authenticatedbased on broadcast request and reply. Join ProcedureFor old_ mg ik : old member of groupLC ik → old_ mgik :{IDLC,KEK_GSGik }old_KEK_ GSG ikLC ik → mgik:{IDLC, TEK, KEK_GSGik}Pub_ mgik Thus the approach of an efficient Group Based Fig. 1 Average end to end delays of multicast transmissionMulticast Hierarchy (GBMH) using Multicastversion SAODV is described in five phases in order The average end to end delays of multicastto have secure multicast communication adhoc transmission is efficient in proposed GBMH.networks. This approaches the issues of end to enddelay in multicast transmission and also toleratesthe fault that occurs due to node failure. As number of nodes increases, it increases the fault- V. PERFORMANCE ANALYSIS tolerance in key distribution. Indeed, this approach divides the multicast group with the effective connectivity between nodes. It allows fast reaction The performance of secure multicast to topology changes. This is due to the fact that itcommunication of the efficient GBMH for adhoc sends acknowledgement for each transmission innetworks in terms of end to end delay and fault order to reduce the retransmission. Hence ittolerance due to node failure is analyzed. This tolerates the fault that occurs due to node failure ofapproach is simulated under Linux Fedora, using multicast transmission in efficient GBMHthe network simulator NS2 version ns-allinone-2.33. compared to OMCT.The performance metrics are namely average end toend delay and fault tolerance of secure multicastcommunication. End to End Delay: The average latency or end toend delay of keys transmission from the source tothe receivers. This metrics allows evaluating theaverage latency to forward a key from a LC to itsgroup members. Fault Tolerance: This metrics allows evaluatingthe percentage of tolerance of fault that occurs dueto node failure. Fig 1 and Fig 2 shows thesimulation results of the comparison of OMCT withGBMH. Fig. 2 Fault Tolerance in multicast communication 235 All Rights Reserved © 2012 IJARCET
  6. 6. ISSN: 2278 – 1323 International Journal of Advanced Research in Computer Engineering & Technology Volume 1, Issue 5, July 2012 [8] Bettahar, H., Bouabdallah, A., Challal, Y.: An adaptive key management protocol for secure multicast. In: Proc. IEEE International Conference on Computer Communications and Networks, October 2002, pp. 190–195 VI. CONCLUSION (2002) [9] Challal, Y., Bettahar, H., Bouabdallah, A.: SAKM: A Scalable and Adaptive Key Management Approach for Multicast Communications. Secure multicast communication in adhoc ACM SIGCOMM Computer Communication Review, 55–70 (April 2004) [10] Bouassida, M., Chrisment, I., Festor, O.: An Enhanced Hybrid Keynetworks is challenging due to its inherent Management Protocol for Secure Multicast in Ad Hoc Networks. In:characteristics of infrastructure-less architecture NETWORKING 2004. LNCS, vol. 3042, pp. 725–742. 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