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Poster Paper Proc. of Int. Conf. on Advances in Computer Engineering 2011

Security Attacks and Solutions in MANET Preeti Sachan1, and Pabitra Mohan Khilar2 1

National Institute of Technology Rourkela, India Email: preetischn@gmail.com 2 National Institute of Technology Rourkela, India Email: pmkhilar@nitrkl.ac.in Abstract—Mobile ad hoc network is a collection of mobile hosts connected by wireless links. Absence of centralized infrastructure such as base station or access point, highly dynamic topology, distributed cooperation, resource constrained nodes and bandwidth constrained wireless links are certain unique characteristics of ad hoc networks that make them highly vulnerable to security attacks compared to wired networks or conventional wireless networks (infrastructure based). In this paper we discuss different types of security attacks that can be launched easily in MANET and related solutions proposed by researchers for ensuring network security. We implement the secure ad-hoc on-demand distance vector routing protocol (SAODV) and compare the performance of protocol with existing AODV protocol in the presence of black hole attack using network simulator tool (NS2).

Authentication, Integrity and Non-repudiation [3], [4]. In ad hoc network routing protocols, confidentiality is not required as routing messages need to be processed by intermediate nodes before forwarding in the network. Moreover nonrepudiation is also not critical services [5]. The rest of this paper is organized as follows: We provide an overview on security attacks against MANET and some solutions proposed by researchers. We implement secure AODV (SAODV) protocol using NS2 simulator tool and evaluate the simulation results. Finally we conclude the paper.

II. SECURITY ATTACKS Many researchers have surveyed on malicious attacks and their countermeasures in mobile ad hoc networks [6]- [8].

An overview of attacks according to the protocol layers has been presented in [9], [10]. The security attacks in MANET can be classified into two categories: passive attacks and active attacks. Passive attacks include eavesdropping, monitoring and traffic analysis. An adversary snoops the data exchanged in the network without modifying it. Since passive attack does not affect the normal operation of data so it is very difficult to detect but passive attack can be easily prevented by using encryption algorithms. An active attack disrupts the normal functioning of system by modifying or dropping the control or data packets. It is mainly two types: external attacks and internal attacks. External attacks are performed by nodes that are not member of network. Internal attacks are from compromised or hijacked nodes and very difficult to prevent. Internal attacks include jamming, sleep deprivation, modification, impersonation or spoofing, fabrication and denial of service attack. The attackers either attempt to disrupt the normal routing function or consume the resources such as battery power and bandwidth. Internal attacks such as blackhole, grayhole, wormhole, flooding and routing attack are most common attacks that can be easily carried out by the adversaries in MANET. Wormhole attack is a type of routing disruption attack [11]. An attacker receives packets at one location and tunnels them to another location of network. The tunnel between two colluding attackers is known as a wormhole attack. An adversary may perform this type of attack to prevent the discovery of routes by disrupting the propagation of routing control messages. Black hole and gray hole attacks are kind of fabrication attack. In black hole attack, a malicious node advertises itself as having fresh and valid rout to the destination node by sending false route request message. In AODV routing protocol [12], an attacker performs blackhole attack by assigning small hop count and very high sequence number to the route reply message. . In this way an attacker can attract all data traffic and misuse or

Index Terms— Mobile ad hoc network, Security attacks, SAODV, Black hole.

I. INTRODUCTION Nowadays, the MANET has been an important research area due to its infrastructure less, self configuration and self maintenance characteristics [1]. Application domains include military operations, emergency and rescue operations, wireless mesh and sensor networks, collaborative and distributed computing [2]. Routing protocol, security, medium access scheme, energy management, quality of service, self organization, protocol multicasting and scalability are major challenges that need to be considered when an ad hoc wireless system is designed. A number of routing protocol for MANET has been proposed over the past years. Routing protocols exchange routing information such as hop count, sequence number, signal strength, geographical information etc. and establish an efficient and feasible route to a destination node using this information. The major issues involved in designing a routing protocol for ad hoc wireless network are nodes mobility, bandwidth constrained wireless channel, resource constrained nodes, error prone shared broadcast wireless channel, hidden and exposed terminal problems. Apart from these, secured communication is very important in applications like military environments.

MANET is highly exposed to security attacks in comparison to traditional wired networks. Lack of central authority, insecure operational environment, shared broadcast channel, limited bandwidth and limited resource availability, lack of association among nodes and physical vulnerability of nodes are some unique characteristics of ad hoc networks that causes difficulty in designing of secured routing protocol.

The five major goals that need to be addressed in order to prevent malicious attack are: Availability, Confidentiality, Š 2011 ACEEE DOI: 02.ACE.2011.02.175

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Poster Paper Proc. of Int. Conf. on Advances in Computer Engineering 2011 drop it. A special case of blackhole is grayhole attack in which a malicious node selectively drops packet coming from or destined to specific node. Flooding attack [13] is kind of denial of service attack and carried out against on demand routing protocols such as AODV, DSR. A malicious node may repeatedly broadcast route request or garbage data message to the destination node that does not exist in the network.

This causes consumption of network bandwidth as well as node’s resources such as battery and computational power.

Routing attacks such as routing table overflow, routing table and cache poisoning, packet replication and rushing attacks are launched against routing protocol to disrupt the operation of the network.

Monitor, the Reputation System, the Path Manager, and the Trust Manager. The protocol detects and isolates misbehaving nodes and also scalable in terms of the total number of nodes in the network. Zapata and Asokan [22] proposed secure AODV (SAODV) protocol that is an extension of AODV and provides security features like authentication, integrity and non-repudiation. The SAODV uses two mechanism digital signature and hash chains to secure routing messages like RREQ, RREP and RRER. The SAODV uses two type of extension: Single Signature and Double Signature. Hash chain and digital signature is transmitted with the AODV message as an extension message. The SAODV requires asymmetric key cryptographic operation therefore the nodes in MANET take considerable amount of time to verify the digital signatures as they have limited battery life and processing power. Moreover verification can be very expensive in case when a malicious node floods routing messages with invalid signatures.

II. SECURITY MECHANISM A number of security mechanisms have been proposed to prevent malicious attacks [14]. Passive attack can be prevented using encryption technique. Digital signature, encryption and authentication methods are useful to provide security of end to end data packet at transport layer as well as routing messages and related parameters at network layer.

To defense active attack intrusion detection system, reputation based system and cooperation enforcement mechanisms should be considered. Hu, Johnson and Perrig designed secure efficient ad hoc distance vector (SEAD) [15] protocol based on the design of DSDV [16]. SEAD protects routing updates from attackers by preventing them to change hop count or sequence number in update packets. The protocol uses efficient one way hash function and can be easily implemented with nodes of limited CPU processing capability.

SEAD is robust against multiple uncoordinated attackers trying to create incorrect routing state in any other node but cannot prevent an attacker to use same metric and sequence number which was used by the recent update message.

ARIADNE is an efficient on-demand secure routing protocol proposed by same author [17]. Design of ARIADNE is based on basic operation of DSR [18]. The protocol uses per hop hashing to verify hop and shared secret key between two parties for message authentication. However it relies on Tesla, an efficient broadcast authentication protocol that needs loose time synchronization. Security-aware routing (SAR) [19] protocol is an on demand routing protocol similar to AODV or DSR. SAR integrates trust level of a node and security attributes as parameters into ad hoc route discovery.

The protocol uses asymmetric key cryptography for encryption/decryption and sequence number as time stamp to stop replay attack. SAR always finds route with a quantifiable guarantee of security. However route may not be shortest path in terms of hop count.

Authenticated routing for ad hoc networks (ARAN) [20] is an on demand protocol based on design of AODV. ARAN uses public key cryptographic mechanism to detect and protect all identified malicious attacks. ARAN provides authentication, message integrity and nonrepudiation services using trusted certificate server. CONFIDANT [21] is reputation based system designed as extension of source routing protocol such as DSR. CONFIDANT consists of four components: The © 2011 ACEEE DOI: 02.ACE.2011.02.175

II. IMPLEMENTATION OF SAODV SAODV [22] is designed to protect only routing messages.

Data packets are not secured. SAODV proposed two alternatives concerning to reply RREQ message. In the first alternative, only destination node is allowed to send reply message and in the second, there is no such limitation. We took first alternative for implementation. We used route request single signature extension (RREQ-SSE) and route reply single signature extension (RREP-SSE) as mentioned in [23]. We did not use double signature extension. The source node signs all fields except the hop count of the AODV messages and the hash field from the SAODV extension. Hop count is mutable field so it is assigned to zero while calculating signature of RREQ or RREP messages. When an intermediate node receives a RREQ, first verify the signature before updating any changes in its routing table or creating a reverse route to that host. Only if the signature is verified, intermediate nodes update or create the route and rebroadcast RREQ otherwise drop it. The destination node receives RREQ, verifies it and sends RREP message with RREP single signature extension. We used SHA hash algorithm [24] and RSA encryption method [25]. We implemented SAODV as an extension to existing implementation of AODV. A. Performance Evaluation The simulation has been performed using network simulator tool NS2 [26]. NS2 is an open-source tool developed by the Information Sciences Institute at the University of Southern California. It is a discrete event simulator and used for simulation of routing, multicast protocols and IP protocols over both wired and wireless networks. NS2 is available on several platforms such as Linux, SunOS and Solaris and can be run under Windows using Cygwin. The simulation experiment is carried out in LINUX platform (FEDORA 11).

The generated trace file is analyzed using Awk language.

Gnuplot is used to graphically visualize the performance metrics. For generating network scenario “setdest” an executable program is used. Mobility model is random waypoint model. The scenario has area size of 1000m x 173

Poster Paper Proc. of Int. Conf. on Advances in Computer Engineering 2011 1000m, 50 nodes, maximum speed of 20 m/s, simulation time of 100 seconds and pause times of 0, 20, 40, 60, 80 and 100 seconds. The IEEE 802.11 is used as MAC layer protocol.

The transmission range of each node is 250m. The tcl file “cbrgen.tcl” is used to create network traffic. The traffic has maximum CBR connection of 20, seed value of 1.0 and packet rate of 4.0 packets/second. In the next section we discuss performance metrics.

B. Performance Metrics To compare the protocols, we used performance metrics such as Packet Delivery Ratio, Route Acquisition Time and Routing Load.  Packet Delivery Ratio: It is ratio of data packets received by destination node to the packets sent by source node.  Route Acquisition Time: It is the difference between the time when first route reply is received by the source node and the time when the source node broadcasts a RREQ.  Normalized Routing Load: The normalized routing load is defined as the ratio of total number of routing control packets sent by all nodes to the total the number of data packets received by the destination nodes.

Normalized Routing Load = (Routing Packets Sent * Size of Routing Packet) / (Received Data Packets * Size of Data Packet).

Figure 1. Pause Time Vs Packet Delivery Ratio (no malicious node)

C. Simulation Result In simulation, we find value of performance metrics for different value of pause time. Each node begins to move random destination by remaining stationary for pause time seconds. A pause time of 0 seconds corresponds to continuous motion (high mobility) and a pause time of 100 seconds (equal to length of simulation) corresponds to no motion (no mobility). We took small simulation time (100 seconds) as SAODV protocol uses public key cryptography so it takes significant amount of time to compute digital signature at each node. We compared SAODV protocol with original AODV protocol in the presence of one malicious node that performs black hole attack. A malicious node attracts all traffic by assigning high sequence number and small hop count to the route reply message (RREP) and absorbs all packets without forwarding them to the destination node.

Figure 1 and 2 shows impact of mobility of nodes on packet delivery ratio. Packet delivery ratio indicates loss rate. Packet loss rate is more in stressful environment (high mobility) therefore PDR increases with increase in pause time. AODV performs better than SAODV when there is no malicious node in network. In presence of malicious node, PDR is much less than SAODV as AODV has no security mechanism to prevent attack.

Figure 2. Pause Time Vs Packet Delivery Ratio (one malicious node)

Route acquisition time is amount of time required to establish a particular route. From figure 3 and 4, the route acquisition time of SAODV is little larger than AODV. In SAODV, only destination node can reply, so time required to establish route to destination node is more. In the presence of malicious node, SAODV needs more time to find out a secure route. Also computation or verification of signatures and hashes takes extra time for path establishment. Normalized routing load is the amount of extra byte transmitted while link is established.

Figure 3. Pause Time Vs Route Acquisition Time (no malicious node)

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Poster Paper Proc. of Int. Conf. on Advances in Computer Engineering 2011 all possible attacks and also decrease performance of network.

In this paper we study routing attacks and different security mechanism to guard against attacks. We also implement SAODV using ns2 and compare with AODV. SAODV performs better in the presence of malicious node. SAODV needs to reduce overhead and processing power requirements due to use of public key cryptography.

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Figure 4. Pause Time Vs Route Acquisition Time (one malicious node)

Figure 5. Pause Time Vs Normalized Routing Load (no malicious node)

Figure 6. Pause Time Vs Normalized Routing Load (one malicious node)

Figure 5 and 6 shows impact of pause time on normalized routing load. In SAODV, control packets contain extra bytes to store digital signatures and hashes for providing security so overhead is more than AODV. CONCLUSIONS MANET needs security mechanism for secure routing of data. Although, a number of secure routing protocols have been proposed for mobile ad hoc networks, they still do not provide better tradeoff between higher security and network performance. Existing secure routing protocols do not cover © 2011 ACEEE DOI: 02.ACE.2011.02. 175

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