An Algebraic Watchdog for Wireless Network Coding

In this paper, we propose a scheme, called the "algebraic watchdog" for wireless network coding, in which nodes can detect malicious behaviors probabilistically, police their downstream neighbors locally using overheard messages, and, thus, provide a secure global "self-checking network". Unlike traditional Byzantine detection protocols which are receiver-based, this protocol gives the senders an active role in checking the node downstream. This work is inspired by Marti et. al.'s watchdog-pathrater, which attempts to detect and mitigate the effects of routing misbehavior. As the first building block of a such system, we focus on a two-hop network. We present a graphical model to understand the inference process nodes execute to police their downstream neighbors; as well as to compute, analyze, and approximate the probabilities of misdetection and false detection. In addition, we present an algebraic analysis of the performance using an hypothesis testing framework, that provides exact formulae for probabilities of false detection and misdetection.Comment: 5 pages, 4 figures, submitted to IEEE International Symposium on Information Theory (ISIT) 2009. This is the final version. The content has been changed to incorporate reviewer comments and recent result

Security and Prioritization in Multiple Access Relay Networks

In this work, we considered a multiple access relay network and investigated the following three problems: 1- Tradeoff between reliability and security under falsified data injection attacks; 2-Prioritized analog relaying; 3- mitigation of Forwarding Misbehaviors in Multiple access relay network. In the first problem, we consider a multiple access relay network where multiple sources send independent data to a single destination through multiple relays which may inject a falsified data into the network. To detect the malicious relays and discard (erase) data from them, tracing bits are embedded in the information data at each source node. Parity bits may be also added to correct the errors caused by fading and noise. When the total amount of redundancy, tracing bits plus parity bits, is fixed, an increase in parity bits to increase the reliability requires a decrease in tracing bits which leads to a less accurate detection of malicious behavior of relays, and vice versa. We investigate the tradeoff between the tracing bits and the parity bits in minimizing the probability of decoding error and maximizing the throughput in multi-source, multi-relay networks under falsified data injection attacks. The energy and throughput gains provided by the optimal allocation of redundancy and the tradeoff between reliability and security are analyzed. In the second problem, we consider a multiple access relay network where multiple sources send independent data simultaneously to a common destination through multiple relay nodes. We present three prioritized analog cooperative relaying schemes that provide different class of service (CoS) to different sources while being relayed at the same time in the same frequency band. The three schemes take the channel variations into account in determining the relay encoding (combining) rule, but differ in terms of whether or how relays cooperate. Simulation results on the symbol error probability and outage probability are provided to show the effectiveness of the proposed schemes. In the third problem, we propose a physical layer approach to detect the relay node that injects false data or adds channel errors into the network encoder in multiple access relay networks. The misbehaving relay is detected by using the maximum a posteriori (MAP) detection rule which is optimal in the sense of minimizing the probability of incorrect decision (false alarm and miss detection). The proposed scheme does not require sending extra bits at the source, such as hash function or message authentication check bits, and hence there is no transmission overhead. The side information regarding the presence of forwarding misbehavior is exploited at the decoder to enhance the reliability of decoding. We derive the probability of false alarm and miss detection and the probability of bit error, taking into account the lossy nature of wireless links

IDLP: an efficient intrusion detection and location-aware prevention mechanism for network coding-enabled mobile small cells

Mobile small cell technology is considered as a 5G enabling technology for delivering ubiquitous 5G services in a cost-effective and energy efficient manner. Moreover, Network Coding (NC) technology can be foreseen as a promising solution for the wireless network of mobile small cells to increase its throughput and improve its performance. However, NC-enabled mobile small cells are vulnerable to pollution attacks due to the inherent vulnerabilities of NC. Although there are several works on pollution attack detection, the attackers may continue to pollute packets in the next transmission of coded packets of the same generation from the source node to the destination nodes. Therefore, in this paper, we present an intrusion detection and location-aware prevention (IDLP) mechanism which does not only detect the polluted packets and drop them but also identify the attacker's exact location so as to block them and prevent packet pollution in the next transmissions. In the proposed IDLP mechanism, the detection and locating schemes are based on a null space-based homomorphic MAC scheme. However, the proposed IDLP mechanism is efficient because, in its initial phase (i.e., Phase 1), it is not needed to be applied to all mobile devices in order to protect the NC-enabled mobile small cells from the depletion of their resources. The proposed efficient IDLP mechanism has been implemented in Kodo, and its performance has been evaluated and compared with our previous IDPS scheme proposed in [1], in terms of computational complexity, communicational overhead, and successfully decoding probability as well