GPSIH: A Generic IP-Based Scheme For Identity Hiding In MANETs.

Transcription

1 GPSIH: A Generic IP-Based Scheme For Identity Hiding In MANETs. Yomna M.Mohsen, Mohamed Hamdy and Mohamed Hashem Computer Systems Department Information Systems Department Ain Shams University Cairo, Egypt Abstract Securing communication in Mobile Ad-hoc Networks (MANETs) is a challenging task due to their mobility nature and the lack of central administration. These features make MANETs more vulnerable to several attacks like identity spoofing and traffic analysis which leads to identity disclosure. Many contributions suggest using anonymous routing protocols to protect identity. However, these solutions are limited on certain routing protocols and can be applied on network layer only. In this paper, a lightweight generic scheme for protecting identity has been proposed. The proposed scheme is based on applying XOR and DES encryption techniques. The main contribution of this scheme is the possibility of applying it on network layer regardless of the applied routing protocol. It can be also integrated easily to lower network layers like MAC layer and the higher layers as well. On the other hand, it can overcome the drawbacks which exist in previous proposals like pair-wise keys and complex computations. The simulation studies are carried out to justify the effectiveness of the proposed scheme considering the network scale and different network services used. I. INTRODUCTION Mobile Ad Hoc Network (MANET) is a self organizing network, where a collection of mobile nodes form a temporary network without using any fixed infrastructure. So each node can participate as a mobile router to choose optimal route and as intermediate node to forward data to the other nodes through wireless radio signals. As a result, MANET can be widely used in applications which has lack of infrastructure such as military applications, conferences, home networking and in commercial sectors. The main features of these networks such as ever-changing topology, shared wireless medium and the lack of fixed infrastructure make them vulnerable to many passive and active attacks [1]. This work focuses on the attacks that can affect the identity of a node like identity spoofing and identity disclosure which happens due to traffic analysis [1]. Several solutions have been proposed to prevent these attacks such as [2], [3], [4] and [5]. Despite these proposals have proved its effectiveness, they still have some problems. In this paper, a generic scheme has been proposed which is based on using a set of lightweight cryptographic techniques. These techniques are applied on IP packet s fields that reveal identity of the nodes (e.g source and destination IP addresses) to protect identity from spoofing or malicious traffic analysis. Two cryptographic techniques have been used, XOR and DES cryptosystem. Both techniques represent two extremes XOR as a trivial technique and DES as a well known symmetric key encryption technique. Although asymmetric key encryption is used in many applications in MANETs, power consumption represents our motivation to use symmetric key for their low energy consumption compared to asymmetric key. This scheme can be applied on any routing protocols at network layer. Moreover, it can work with lower network layer and higher layers as well. Also, it overcomes the problems exist in the previous proposals. As using encryption techniques is expected to consume longer time, we study in our work the effect of using our scheme on mainly the transport services present either connectionoriented, connection-less or both. For example, TCP (Transport Control Protocol) is a connection-oriented transport protocol which ensures a reliable data delivery over network. TCP is mainly used in applications that require high reliability and transmission time is relatively less critical like HTTP and FTP. In contrast, UDP (User Datagram Protocol) is a connectionless transport protocol, which ensures delivering data in time, regardless whether the data is transmitted correctly or not (no error checking or error correction). UDP is widely used in the applications which need fast and efficient transmission like audio and video streaming. Both mentioned protocols represent the two transportation services extremes. Nevertheless, there are many other transport services that act between these two extremes like SCTP. SCTP (Stream Control Transmission Protocol) is a transport layer protocol which can serve like TCP or UDP. It supports a reliable transfer of messages as TCP and unordered data delivery like UDP. In addition, it provides some additional features that not found in TCP or UDP like multi-homing, which means that end points can use multiple IP addresses for the connection [6]. Because transport layer protocols are originally designed for wired networks, solutions like [7], [8] have tried to improve their performance in MANETs, as they face many challenges like network partitioning, channel errors and frequent mobility [9]. In our work, we study the effect of our scheme on these protocols in terms of transmission time and reliability. The paper is organized as follows: related work is discussed in section 2, underlying models are explained in section 3, section 4 explains our scheme, while section 6 discusses security analysis, section 7 discusses experimental results and section 8 provides conclusion. II. RELATED WORK Several contributions have been proposed to secure node identity in MANET as in [10], [11]. In Secure Ad hoc On- CNs-32

2 Demand Distance Vector Routing SAODV [10], two techniques have been used for securing identity, digital signature for authenticating non-mutable fields of messages (route request and route reply messages) and hash chains for securing mutable fields (hop count field) of the same messages. Although the proposed solution is effective, but it is limited only on AODV and cannot applied on other routing protocols. In addition, it uses asymmetric cryptography which consumes more power. Multi-factor authentication framework is proposed in [11]. In this framework, the authentication process is done by combining cryptographic techniques with information comes from physical node characteristics (e.g transmission coverage, radio frequency fingerprint [12]). The proposed framework needs additional sensitivity capabilities from mobile nodes. Despite Anonymous communication has been studied extensively in wired networks such as [13], [14]. But due to the special characteristics of MANET the previous proposals are inapplicable to ad-hoc networks. Anonymous communication in general tries to achieve sender anonymity, recipient anonymity, relationship anonymity and pseudonymity [15]. Zhang in [16] proposed the Anonymous On-Demand Routing MASK. In this protocol, the neighboring nodes are allowed to authenticate each other without appearing with their real identities, instead they use set of pseudonyms. Moreover, it uses pairing technique which allows nodes to form pairs of shared session key and link identifier (Skey, LinkID) for protecting the transmitted packets between them without revealing the real identities of sender and receiver. Kong and Hong proposed An Anonymous On-Demand Routing Protocol ANDOR in [3]. ANODR achieves identity privacy by using Onion Routing [17]. In this type of routing, route request forwarder generates encryption layers, and in route reply one layer is reduced in each step. Symmetric key has been used in Onion Routing production. A Secure Distributed Anonymous Routing Protocol SDAR has been proposed in [18], In this protocol, source node initiates some trust requirements with its path discovery message, intermediate nodes satisfy these requirements by encrypting their identifications (IDs) and forward the message to the neighboring nodes, only destination node will be able to decrypt collected (IDS), the destination gathers these (IDS) in a reply message and sends back to the source node. While Anonymous Routing Protocol ARM in [2] applies random padding and random TTL values for route request and route reply messages beside using traditional pseudonyms and asymmetric key pairs. So ARM is quite effective against passive attacks. Javier Campos in [4] presents HOP. It is a novel solution based on enhancing HIP (Host Identity Protocol) [19] to offer anonymity in MANET and integrates it with OLSR [20] and pseudonyms. PseudoAODV in [5] has been proposed. It is a modified version of AODV in which original identifier (IP/Mac) addresses are replaced with random pseudonyms [21]. Zhao and Aggarwal in [22] suggest General-purpose Identity Hiding Schemes. A general identity hiding scheme has been proposed which is based on popular cryptosystems like (AES, RSA, or ELGamal). The main idea of the proposed scheme is to encrypt the identity of the nodes which is represented by source and destination IP addresses. This general scheme tries to overcome the drawbacks of previous proposals which depend on certain routing protocols and cannot be applied in lower or higher layers. However, this scheme is not practically tested. In this work, we implement the previously mentioned scheme using XOR and DES cryptosystem and test it practically using network simulator. III. A. Network Model UNDERLYING MODELS We assume that wireless links between nodes are symmetric, thus if node X is in the transmission range of node Y, then Y is in the transmission range of X. These nodes are called neighboring nodes. In contrast, non-neighboring nodes can communicate with each other via multi-hop wireless links. Furthermore, we assume that node s medium access control (MAC) interface has the ability to broadcast MAC frames to all neighboring nodes, or unicasts MAC frames to specific node within its transmission range. Also, each mobile node has the capability to obtain the MAC address of certain IP address through enabling address resolution protocol (ARP). Moreover, it is assumed that there is a symmetric-key distribution service for distributing symmetric keys between mobile nodes before communication. B. Threat Model The mobile nature of MANET and the lack of fixed infrastructure, making it liable to active or passive attacks. Active attacker tries to perform visible attacks. The attacker can have direct access to the network resources, so it can alter the data transmitted across network. In addition, it can impersonate the other nodes identity, so all the messages received directed to the fake node. Which represents a big challenge for securing communication in MANET. In contrast, passive attacker does not disrupt MANET basic operations (e.g modify or drop packet). Instead, it listens to communication to infer sensitive information which may be related to the network applications or identity of communicating nodes (e.g traffic analysis). However, passive attacker is more dangerous than active attacker, as passive attacker is invisible and hard to detect. Furthermore, we assume that passive or active attackers have limited computing resources. They do not have the capabilities to easily read the encrypted identities, especially that symmetric key encryption cannot be decrypted in a reasonable amount of time. So the encrypted data is totally secured. IV. THE GPSIH The generic ip-based scheme for identity hiding in mobile ad hoc networks (GPSIH) is designed to secure identity of communicating node at the network layer. In this section, the main requirements, main phases and methodology of proposed scheme are described. A. Requirements Although the identities are totally encrypted, still passive attacker can apply traffic analysis on encrypted identities and infers some real information about them. So our scheme must meet the following characteristics: 1)IP packet should look random all the time. CNs-33

3 2)The encryption and decryption processes should be done only by genuine nodes not by malicious nodes. 3)Packet format should follow IPv4 format. 4)Size of the key used in encryption is 64 bits. Regular encryption systems fail to meet the first requirement, as they cannot generate random output for the same input (identity). Random value should be added to the fixed input. In our scheme, this random value is placed in the option field in the IP packet. So in decryption process the receiver node can obtain random value and gets actual identity. B. Main phases 1) Sending phase: In sending phase, genuine node encrypts its identity (e.g source IP address) and destination address which it will send IP packet to, then the node sends the packet to its neighbors. On the other hand, the malicious node in that case sends its packet without any type of locking. Algorithm 1 sending phase if malicious node then send packet without encrypting src. and dest. else if genuine node then packet is sent with encrypted src. and dest. 2) Receiving phase: In receiving phase, genuine node decrypts the source and destination IP addresses, it checks first if these addresses after decryption are valid values (have the same network address) or not. If they are valid, it checks whether the destination address of packet matches its address or not, if it matches so it sends a reply message and caches the packet. If no matching happens, it forwards the packet to its neighbors. If the decrypted addresses are not valid values, then this packet comes from malicious node so the packet is discarded. On the other side, the malicious node tries to spoof or eavesdrop any source address presents in the received packet, but due to encryption it fails to do so. Algorithm 2 receiving phase if malicious node then src is encrypted, spoofing failed. else if genuine node then decrypt src. and dest. of received packet. if src.&dest. have valid values then packet comes from genuine node. if dest = received then send route reply then cache packet. else if dest.!= received then packet is forwarded to the neighbors. else if src&dest. have not valid values then packet is discarded. 3) Forwarding phase: In forwarding phase, genuine node can forward any packet that not destined for it to its neighbors, as it can recognize the next hop it forwards the packet to. In Algorithm 3 forwarding phase if malicious node then node discards the packets. else if genuine node then node forwards any received packet. contrast, malicious node cannot as next hop address is totally encrypted, so it stops forwarding any packet. Moreover, our scheme uses a symmetric key of size 64 bits, the source and destination IP addresses each of size 32 bits, the addresses are transformed into binary values and encryption is done on 64 bit block (source and destination addresses) together. Two random values of size 32 bits are generated and are added on each address before encryption. These random values are transmitted into special field (option field) in the IP packet(as shown in Figure ), so the receiver on the other side can obtain them and make decryption. Fig. 1. IPv4 packet format C. AODV vs GPSIH Although our scheme is working on any routing protocol, In this paper, it is applied on AODV as a proof of concept. In AODV, malicious nodes can participate in the network activities. In other words, IP packets that are sent or forwarded by malicious nodes are not discarded by genuine nodes. In addition, malicious nodes can impersonate identity of sender node without being detected. V. SECURITY ANALYSIS This section presents an analysis on the security goals that can be achieved by our scheme. The security goals aim to prevent identity spoofing, identity disclosure and their effects. A. Traffic Analysis As mentioned previously, traffic analysis as shown in Figure 2, is a passive attack which aims to infer some sensitive information about network which may be related to the identities of the communicating parties. The passive attack can not be launched by malicious node, as the identity of the nodes changes randomly. CNs-34

4 TABLE I. SCENARIO PARAMETERS Fig. 2. An example of traffic analysis attack B. Impersonation Attack In impersonation attack, the malicious node tries to assume the identity of genuine node, so the received messages are directed to the node it fakes. Because the identity is hidden, impersonation attack can not be launched. Figure 3 describes impersonation attack. Parameter Simulation time Wireless radio range Value 400 sec 200 m Mobile nodes 25 Traffic type Mobility model Pause time Network model id Network service P acketdeliveryratio(ρ) = CBR 512-bytes packet Random Way Point model 10 sec IPv4 TCP ΣNumberofReceivedP ackets ΣNumberofSentP ackets (1) Packet Drop Ratio: Is the number of IP packets dropped by all nodes across entire network. End-to-End Delay: Is the time elapsed between the creation of IP packet at the source node and its arrival at destination. Fig. 3. An example of impersonation attack In Figure 3, node S wants to send packet to node X, but S cannot send packet directly to X, so X sends to its neighbors a request to forward packet. A malicious node M is closer to S than X, then M impersonates X to be X, so any packet destined to node X will be received by X. C. ARP Spoofing ARP stands for (Address Resolution Protocol). ARP translates IP address of node into MAC address using ARP s cache. So packet can be sent over data-link layer. Malicious nodes can perform ARP spoof attack, when node A for example sends ARP request to its neighbors to get MAC address of node B, a malicious node replies with spoofed ARP reply associating its MAC address with node B IP address, so any information will be sent from node A to node B will instead be received by malicious node. Our scheme can prevent ARP spoof as it hides sender and receiver IP address. VI. EXPERIMENTAL RESULTS In this section, simulation studies are discussed. The simulation is done by using OPNET modeler to evaluate the performance of the proposed scheme by varying number of misbehaving nodes in the network. The metrics used to analyze performance of our work are the following: Packet Delivery Ratio: It is defined as the total number of received packets by destinations divided by total number of sent packets by sources. A. Simulation Model The proposed technique is evaluated by comparing it with normal AODV. The network scenario parameters are listed in the Table I. The simulation scenario consists of 25 mobile nodes placed randomly in 700 m x 700 m which are moving according to random way mobility model with speed ranging from 1 to 3 m/sec and pause time 10 sec. The transmission range of the node is 200 m. Constant bit rate (CBR) traffic is used to generate data over network. In each traffic session, packet of size 512 bytes is generated with transmission rate 4 packets/sec. The data is collected by taking the average of a four simulation run, each simulation run takes 400 sec. finally the network service used in our scenario is TCP, it is more complex than UDP as data can be sent bidirectional. As a result, TCP consumes much time and bandwidth, so it will be an appropriate choice for testing our scheme. B. Simulation Results This section discusses simulation results of the AODV before and after applying our proposed scheme. Figures 4, 5 and 6 show comparison between our scheme which is based on modified version of AODV, through using DES and XOR with random number to hide IP address versus normal AODV according to the mentioned metrics. It is clear that packet delivery ratio of proposed scheme as shown in Figure 4, has increased generally compared to normal AODV. Packet delivery ratio of AODV is better than our scheme when there is no misbehaving nodes. When number of misbehaving nodes increases to 5 nodes, the packet delivery ratio is 40 % for AODV whereas it is 50 % and 51 % when using random DES and random XOR, respectively. This is because the normal AODV don t prevent impersonation attack, so when some nodes appear with the same identity the delivery of the packets is not consistent. CNs-35

5 Fig. 4. Packet Delivery Ratio vs number of Misbehaving nodes Fig. 6. End To End Delay vs number of Misbehaving nodes Figure 5 shows that packet drop ratio of our scheme has increased compared to AODV. When there is no misbehaving nodes, packet drop ratio is almost similar for our scheme and AODV. But when number of misbehaving nodes increases, packet drop ratio has increased when using random DES and random XOR, whereas it is approximately 0% for AODV. This is due to excluding malicious nodes from participating in the network and dropping any packet comes from them. ratio, still packet drop ratio in Figure 8 increases as number of misbehaving nodes increases. In contrast, end-to-end delay of proposed scheme in Figure 9 is still less than normal AODV even if number of genuine nodes decreases and mobility increases. Fig. 7. Packet Delivery Ratio vs number of Misbehaving nodes Fig. 5. Packet Drop Ratio vs number of Misbehaving nodes As shown in Figure 6, the end-to-end delay of our scheme decreases as number of misbehaving nodes increases. In contrast, it increases in AODV when number of misbehaving nodes increases. Even though the modified scheme has a fixed encryption-decryption delay, it still has less delay time than AODV. C. Extended Analysis In this section, we discuss the simulation results of our scheme when mobile nodes speed increases up to 10 m/sec. As shown in Figure 7, packet delivery ratio of the proposed scheme still performs better than normal AODV even if mobility of the nodes increases. The same for packet drop VII. CONCLUSION In this paper, we propose A Generic IP-Based Scheme For Identity Hiding In Manets, called GPSIH, to protect identity of the nodes from impersonation and passive eavesdrop by hiding node s IP address. Our scheme is based on using some popular cryptosystems. Compared to previous research, our GPSIH has the following advantages: it can be applied not only on any routing protocols, but also on lower and higher layers applications as well. It avoids using large set of pseudonyms and pair-wise keys which are used by previous proposals. Based on analysis of results, the proposed GPSIH is proved to have a better performance than traditional AODV when CNs-36

6 Fig. 8. Fig. 9. Packet Drop Ratio vs number of Misbehaving nodes End To End Delay vs number of Misbehaving nodes number of the misbehaving nodes increases up to 20 %, thus packet delivery ratio increases by 10 % and end-to-end delay decreases by 27 %. So, the proposed scheme guarantees a reliable delivery of data and a reasonable transmission time which has a better effect on the performance of TCP and UDP services, respectively. In addition, GPSIH still outperforms when the speed of mobile nodes increases. Finally, The size of IP address before and after encryption remains the same. So the bandwidth of the network is not affected. Therefore our GPSIH can act as a reliable generic scheme for MANETs when identity hiding is required. ACKNOWLEDGMENT The authors would like to thank National Telecommunication Institute (NTI) Cairo, Egypt for helping us in obtaining Opnet modeler 17.0 license. REFERENCES [1] B. W. J. C. J. W. M. Cardei, Wireless Network Security. Springer, 2007, ch. A Survey of Attacks and Countermeasures in Mobile Ad Hoc Networks, pp [2] S. Seys and B. Preneel, Arm: Anonymous routing protocol for mobile ad hoc networks, International Journal of Wireless and Mobile Computing, vol. 3, no. 3, pp , Oct [3] J. Kong and X. Hong, Anodr: Anonymous on demand routing with untraceable routes for mobile adhoc networks, in 4th ACM international symposium on Mobile ad hoc networking & computing, ser. MobiHoc 03. ACM, 2003, pp [4] J. Campos, C. T. Calafate, M. Nacher, PietroManzoni, and J.-C. Cano, Hop: Achieving efficient anonymity inmanets by combining hip, olsr, and pseudonyms, EURASIP Journal on Wireless Communications and Networking, vol. 2011, pp , september [5] M. Y. Reza Shokri and N. Yazdani, Anonymous routing in manet using random identifiers, in Sixth International Conference on Networking, ser. ICN 07. Sainte-Luce, Martinique, France: IEEE, 2007, p. 2. [6] M. A. A. S. S. M. S. Hatim Mohamad Tahir, Abas Md Said and S. H. Abdi, Performance comparison of sctp and udp over mobile ad hoc networks, International Journal of Computer Science, vol. 9, no. 2, july [7] F. Wang and Y. Zhang, Improving tcp performance over mobile ad-hoc networks with out-of-order detection and response, in Proceedings of the 3rd ACM International Symposium on Mobile Ad Hoc Networking, ser. MobiHoc 02. EPFL Lausanne, Switzerland: ACM, 2002, pp [8] W.-Q. Xu and T.-J. Wu, Tcp issues mobile ad hoc networks: Challenges and solutions, Journal of Computer Science and Technology, Springer, [9] U. Ibom, Tcp performance over manet, in International Conference on Information Networking, ser. ICOIN. Busan, Korea: IEEE, JAN [10] M. G. Zapata, Secure ad hoc on-demand distance vector routing, ACM SIGMOBILE Mobile Computing and Communications Review, vol. 6, no. 3, pp , july [11] P. K. Dimitris Glynos and C. Douligeris, Preventing impersonation attacks in manet with multi-factor authentication, in Proceedings of the Third International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks., ser. WIOPT 05. Trentino, Italy: IEEE, 2005, pp [12] M. B. Jeyanthi Hall and E. Kranakis, Detection of transient in radio frequency fingerprinting using signal phase, in International Conference on Wireless and Optical Communications, ser. WOC, Banff, Canada, Jul [13] M. K. Reiter and A. D. Rubin, Crowds: Anonymity for web transactions, ACM Transactions on Information and System Security, vol. 1, no. 1, pp , Nov [14] D. L. Chaum, Untraceable electronic mail, return addresses, and digital pseudonyms, Communications of the ACM, vol. 24, no. 2, pp , feb [15] M. N. acher, C. T. Calafate, J.-C. Cano, and P. Manzoni, An overview of anonymous communications in mobile ad hoc networks, WIRELESS COMMUNICATIONS AND MOBILE COMPUTING, vol. 12, no. 8, p , june [16] Y. Z. W. Liu and W. Lout, Anonymous communications in mobile ad hoc networks, in INFOCOM, vol. 4. IEEE, 2005, pp [17] P. F. S. M. G. Reed and D. M. Goldschlag, Anonymous connections and onion routing, IEEE Journal on Selected Areas in Communications, vol. 16, no. 4, pp , sep [18] L. X. Azzedine Boukerche, Khalil El-Khatib and L. Korba, Sdar: A secure distributed anonymous routing protocol for wireless and mobile ad hoc networks, in 29th IEEE International Conference on Local Computer Networks, ser. LCN 04. Tampa, FL, USA: IEEE, 2004, pp [19] a. T. H. Pekka Nikander, Andrei Gurtov, Host identity protocol (hip): Connectivity,mobility, multi-homing, security, and privacy over ipv4 and ipv6 networks, IEEE Comm. Surveys, vol. 12, no. 2, pp , April [20] T. C. A. L. A. Q. L. V. P. Jaquet, P. Muhlethaler, Optimized link state routing protocol for ad hoc networks, in Multi Topic Conference, ser. INMIC. Lahore, Pakistan: IEEE, Dec 2001, pp [21] A. Pfitzmann and M. Khntopp, Anonymity, unobservability, and pseudeonymity a proposal for terminology, in International Work- CNs-37

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