Security analysis in mobile ad hoc networks

¶ … Mobile Adhoc Networks (manet)

The work of Corson and Macker (1999) entitled: "Mobile Ad Hoc Networking (MANET)" reports that advancements in computer and wireless communications technologies in recent years expectations are that advanced mobile wireless computing is expected to see increasingly widespread use and application, much of which will involve the use of Internet Protocol (IP) suite." (Corson and Macker, 1999)

Mobile ad hoc networking was envisioned as supporting operation in mobile wireless networks that is robust and efficient through incorporation of routing functionality into mobile nodes. These types of networks are viewed as being dynamic and rapidly changing in nature, "random, multihop topologies which are likely composed of relatively bandwidth-constrained wireless links." (Corson and Macker, 1999)

It was reported at that time that routing support for mobile hosts "is presently being formulated as 'mobile IP' technology which is designed to support "nomadic host 'roaming' where a roaming host may be connected through various means to the Internet other than its well-known fixed-address domain space. The host may be directly physically connected to the fixed network on a foreign subnet or be connected via wireless link, dial-up line, etc." (Corson and Macker, 1999)

Corson and Macker state that Mobile ad hoc Networking is similar to Mobile Packet Radio Networking as well as Mobile Mesh Networking, and Mobile, Multihop, Wireless Networking. The need for dynamic ad hoc networking technology is one stated to be both "current and future" and some applications of MAET technology might include "industrial and commercial applications involving cooperative mobile data exchange" in addition to "mesh-based mobile networks...operated as robust, inexpensive alternatives or enhancements to cell-based mobile network infrastructures." (Corson and Macker, 1999) The military is in need of and will continue to need networking for "robust, IP-compliant data services within mobile wireless communication networks." Many of which are comprised of "highly-dynamic autonomous topology segments." (Corson and Macker, 1999)

A. Characteristics of MANETS

A MANET is stated to be comprised by "mobile platforms (e.g., a router with multiple hosts and wireless communications devices) herein simply referred to as 'nodes' which are free to move about arbitrarily." (Corson and Macker, 1999) The nodes are stated to be located in or on airplanes, ships, trucks, cars and even on people or small devices with multiple hosts per router possible. A MANET is stated to be an "autonomous system of mobile nodes" which may "operate in isolation, or may have gateways to go and interface with a fixed network internetwork." (Corson and Macker, 1999) Stub networks carry traffic originating at and/or destined for internal nodes, but do not permit exogenous traffic to 'transit' through the stub network." (Corson and Macker, 1999)

MANET nodes are equipped with "wireless transmitters and receivers using antennas which may be omnidirectional (broadcast), and highly directional (point-to-point), possibly steerable, or some combination thereof." (Corson and Macker, 1999) There are stated to be several "salient characteristics' of MANETS:

(1) Dynamic topologies: Nodes are free to move arbitrarily; thus, the network topology -- which is typically multihop -- may change randomly and rapidly at unpredictable times, and may consist of both bidirectional and unidirectional links; and (2) Bandwidth-constrained, variable capacity links: Wireless links will continue to have significantly lower capacity than their hardwired counterparts. In addition, the realized throughput of wireless communications -- after accounting for the effects of multiple access, fading, noise, and interference conditions, etc. -- is often much less than a radio's maximum transmission rate.

(3) Energy-constrained operation: Some or all of the nodes in a MANET may rely on batteries or other exhaustible means for their energy. For these nodes, the most important system design criteria for optimization may be energy conservation.

(4) Limited physical security: Mobile wireless networks are generally more prone to physical security threats than are fixed-cable nets. The increased possibility of eavesdropping, spoofing, and denial-of-service attacks should be carefully considered. Existing link security techniques are often applied within wireless networks to reduce security threats. As a benefit, the decentralized nature of network control in MANETs provides additional robustness against the single points of failure of more centralized approaches. (Corson and Macker, 1999)

B. Focus of Market Research

The focus of the market research herein is the MANET and the potential for future expansion and application of the MANET. This will be accomplished through a qualitative review of literature on mobile ad hoc wireless networks. The work entitled: "A Survey on Attacks and Countermeasures in Mobile Ad Hoc Networks" reports that security is a service that is "essential service for wired and wireless network communications. The success of Mobile Ad hoc Networks (MANET) strongly depends on people's confidence in its security. However, the characteristics of MANET pose both challenges and opportunities in achieving security goals, such as confidentiality, authentication, integrity, availability, access control, and non-repudiation. This paper provides a survey on attacks and countermeasures in MANET. The countermeasures are features or functions that reduce or eliminate security vulnerabilities and attacks."

Gaertner and Cahill (2004) write that mobile ad hoc wireless networks currently have low communication quality."

Liu, Chen, Fang and Shea (2004) write of mobile ad hob wireless networking that "Due to the salient characteristics such as the time-varying and error-prone wireless links, the dynamic and limited bandwidth, the time-varying traffic pattern and user locations, and the energy constraints, it is a challenging task to efficiently support heterogeneous traffic with different quality of service (CoS) requirements in multihop mobile ad hoc networks." It is reported that "many channel-dependent mechanisms are proposed to address this issue based on the cross-layer design philosophy. However, a lot of problems remain before more efficient solutions are found. One of the problems is how to alleviate the conflict between throughput and fairness for different prioritized traffic, especially how to avoid the bandwidth starvation problem for low-priority traffic when the high-priority traffic load is very high. In this paper, we propose a novel scheme named Courtesy Piggybacking to address this problem. With the recognition of interlayer coupling, our Courtesy Piggybacking scheme exploits the channel dynamics and stochastic traffic features to alleviate the conflict. The basic idea is to let the high-priority traffic help the low-priority traffic by sharing unused residual bandwidth with courtesy. Another noteworthy feature of the proposed scheme is its implementation simplicity: The scheme is easy to implement and is applicable in networks using either reservation-based or contention-based MAC protocols." (Liu, Chen, Fang, and Shea, 2004)

The work of Chlamtac, Conti and Liu (2003) entitled: "Mobile Ad Hoc Networking: Imperatives and Challenges" states that MANETS "represent complex distributed systems that comprise wireless mobile nodes that can freely and dynamically self-organize into arbitrary and temporary 'ad-hoc' network topologies, allowing people and devices to seamlessly internetwork in areas with no pre-existing communication infrastructure, e.g. disaster recovery environments." The recent introduction of new technologies including Bluetooth, IEEE 802.11 and Hyperlan are "helping enable eventual commercial MANET deployments outside the military domain."

Chlamtac, Conti, and Liu (2003) state that a primary goal in the 4G wireless evolution is the provision of "...pervasive computing environments that can seamlessly and ubiquitously support users in accomplishing their tasks, in accessing information or communicating with other users at anytime, anywhere, and from any device . In this environment, computers get pushed further into background; computing power and network connectivity are embedded in virtually every device to bring computation to users, no matter where they are, or under what circumstances they work." Stated to be the new trend is helping users in everyday tasks through exploitation of both technologies and infrastructures "hidden in the environment without requiring any major change in the user's behavior." It is stated that the new trend has as its basis the concept of "Ambient Intelligence" which has as its objective the "...integration of digital devices and networks into the everyday environment, rendering accessible, through easy and "natural" interactions, a multitude of services and applications. Ambient intelligence places the user at the center of the information society. This view heavily relies on 4G wireless and mobile communications. 4G is all about an integrated, global network, based on an open systems approach. Integrating different types of wireless networks with wire-line backbone network seamlessly, and convergence of voice, multimedia and data traffic over a single IP-based core network are the main foci of 4G. With the availability of ultra-high bandwidth of up to 100 Mbps, multimedia services can be supported efficiently; ubiquitous computing is enabled with enhanced system mobility and portability support, and location-based services are all expected." (Chlamtac, Conti, and Liu, 2003)

The following figure illustrates the networks and components in the 4G network architecture.

Figure 1

Source: Chlamtac, Conti, and Liu (2003)

It is stated that 4G networks are held out to be "hybrid broadband networks that integrate different network topologies and platforms." (Chlamtac, Conti, and Liu, 2003) Figure 1 shows the overlapping of different network boundaries which is stated to represent the "integration of different types of networks in 4G. There are stated to be two levels of integration:

(1) First is the integration of heterogeneous wireless networks with varying transmission characteristics such as Wireless LAN, WAN, PAN, as well as mobile ad hoc networks; and (2) At the second level is the integration of wireless networks with the fixed network backbone infrastructure, the Internet, and PSTN. Much work remains to enable a seamless

Integration, for example that can extend IP to support mobile network devices. (Chlamtac, Conti, and Liu, 2003)

4G is stated to begin with the assumption "that future networks will be entirely packet-switched, using protocols evolved from those in use in today's Internet." (Chlamtac, Conti, and Liu, 2003) It is reported that a 4G wireless network that is all IP-based "has intrinsic advantages over its predecessors." (Chlamtac, Conti, and Liu, 2003)

IP is stated to be both compatible with and independent of "the actual radio access technology" meaning that 'the core 4G network can be designed and evolves independently from access networks. Using IP-based core network also means the immediate tapping of the rich protocol suites and services already available, for example, voice and data convergence, can be supported by using readily available VoIP set of protocols such as MEGACOP, MGCP, SIP, H.323, SCTP. Finally the converged all-IP wireless core networks will be packet based and support packetized voice and multimedia on top of data. This evolution is expected to greatly simplify the network and to reduce costs for maintaining separate networks, for different traffic types." (Chlamtac, Conti, and Liu, 2003)

It is reported that 4G IP-based systems will be cheaper and more efficient than 3G. The basis for this is first that equipment costs are forecasted to be "four to ten times lower than equivalent circuit-switched equipment for 2G and 3G wireless infrastructures." (Chlamtac, Conti, and Liu, 2003) In addition, an open converged IP wireless environment brings about a reduction in costs for network build-out and maintenance and that will not be a requirement for purchasing extra spectrum since 2G/3G spectrum can be reused in 4G and the majority of the spectrum required by WLAN and WPAN is public and therefore does not make a requirement of a license.

It is reported that MANETS have been used mainly for "tactical network related applications to improve battlefield communications survivability" as the dynamic nature of military operations means that military cannot rely on access to fixed pre-placed communication infrastructure in battlefield." (Chlamtac, Conti, and Liu, 2003)

Mobile ad hoc networks are stated to create a "suitable framework to address the issues in radio signal limitations and specifically interference through provision of a multi-hop wireless network without pre-placed infrastructure and connectivity beyond LOS." (Chlamtac, Conti, and Liu, 2003)

Ad hoc wireless networks are stated to inherit the traditional problems of wireless communications and wireless networking:

(1) The wireless medium has neither absolute nor readily observable boundaries outside of which stations are known to be unable to receive network frames;

(2) The channel is unprotected from outside signals;

(3) The wireless medium is significantly less reliable than wired media;

(4) The channel has time-varying and asymmetric propagation properties; and (5) hidden-terminal and exposed-terminal phenomena may occur. (Chlamtac, Conti, and Liu, 2003)

C. MANET Applications

Chlamtac, Conti and Liu (2003) report the MANET applications listed in Figure 2.

Figure 2

MANET Applications

Source: Chlamtac, Conti, and Liu (2003)

D. MANET Security Issues

It is reported that an issue that presents great challenges is securing the wireless ad hoc networks and that toward this end understanding the possible types of attacks that may occur is the first step towards development of good solutions for security. Ad hoc networks are stated to "have to cope with the same kinds of vulnerabilities as their wired counterparts as well as with new vulnerabilities specific to the ad hoc context." (Chlamtac, Conti, and Liu, 2003)

Traditional vulnerabilities are further emphasized in the ad hoc environment. It is reported that passive attack involves the attacker listening to the network rather than sending information and this type of passive attack does not actually interrupt the operation of a protocol but instead attempts to mine information that would be valuable. However, the active attack is different in that information is inserted into the network.

Wireless mobile ad hoc networking in its very nature results in new security challenges in the design of MANET networks. These types of networks are reported to be "generally more vulnerable to information and physical security threats." (Chlamtac, Conti, and Liu, 2003) Vulnerability includes those to:

(1) Channels and modes; and (2) Absence of infrastructure and dynamically changing topology, all serve to make the network security of the MANET one that is difficult in nature. (Chlamtac, Conti, and Liu, 2003)

Factors affecting the security of MANETS include:

(1) Broadcast wireless channels allow message eavesdropping and injection;

(2) Nodes do not reside in physically protected places and easily fall under the attackers' control;

(3) The absence of infrastructure makes the classical security solutions based on certification authorities and online servers inapplicable and (4) The security of routing protocols in the MANET dynamic environment is an additional challenge. (Chlamtac, Conti, and Liu, 2003)

Active attacks are categorized as follows:

(1) IMPERSONATION. In this type of attack, nodes may be able to join the network undetectably, or send false routing information, masquerading as some other trusted node. The Black Hole attack falls in this category: here a malicious node uses the routing protocol to advertise itself as having the shortest path to the node whose packets it wants to intercept. A more subtle type of routing disruption is the creation of a tunnel (or Wormhole) in the network between two colluding malicious nodes;

(2) DENIAL OF SERVICE. The Routing Table Overflow and the Sleep Depravation attacks fall in this category. In the former, the attacker attempts to create routes to non-existent nodes to overwhelm the routing-protocol implementations. In the latter, the attacker attempts to consume batteries of other nodes by requesting routes, or by forwarding unnecessary packets; and (3) DISCLOSURE ATTACK. A location disclosure attack can reveal something about the physical location of nodes or the structure of the network. Two types of security mechanisms can generally be applied: preventive and detective. Preventive mechanisms are typically based on key-based cryptography. Keys distribution is therefore at the center of these mechanisms. Secret keys are distributed through a pre-established secure channel, and this makes symmetric cryptography generally difficult to apply in ad hoc networks. Public keys are distributed through certificates that bind a public key to a device. In the centralized approach, certificates are provided, stored, and distributed by the Certificate Authority. Since no central authority, no centralized trusted third party, and no central server are possible in MANET, the key management function needs to be distributed over nodes. (Chlamtac, Conti, and Liu, 2003)

It is stated that Bluetooth and 802.11 "...implement mechanisms based on cryptography to prevent unauthorized accesses, and to enhance the privacy on radio." Chlamtac, Conti, and Liu, 2003) Wired Equivalent Privacy (WEP) provides security in the IEEE 802.11 standard. WEP is stated to support "...both data encryption and integrity. The security is based on a 40-bit secret key. The secret key can either be a default key shared by all the devices of a WLAN, or a pairwise secret key shared only by two communicating devices. " (Chlamtac, Conti, and Liu, 2003)

WEP does not provide support for the exchange of pair-wise secret keys as it must be manually installed on each of the devices. Furthermore, WEP is stated to suffer "from design flaws and weaknesses, to correct the WEP problems a task group part of the IEEE 802.11i standardization is designing the new 802.11 security architecture." (Chlamtac, Conti, and Liu, 2003)

Cryptographic security mechanisms are used by Bluetooth which are reported to be implemented in the data layer link and it is stated that "a key management service provides each device with asset of symmetric cryptographic keys required for the initialization of a secret channel with another device, the execution of an authentication protocol, and the exchange of encrypted data on the secret channel." (Chlamtac, Conti, and Liu, 2003)