We study oblivious deterministic gossip algorithms for multi-channel radio networks with a malicious adversary. In a multi-channel network, each of the n processes in the system must choose, in each round, one of the c channels of the system on which to participate. Assuming the adversary can disrupt one channel per round, “preventing“ communication on that channel, we establish (1−ɛ)n a tight bound of max Θ c−1 + logc n n(1−ɛ), Θ ɛc2 ”” on the number of rounds needed to solve the ɛ-gossip problem, a parameterized generalization of the all-to-all gossip problem that requires (1 − ɛ)n of the “rumors ” to be successfully disseminated. Underlying our lower bound proof lies an interesting connection between ɛ-gossip and extremal graph theory. Specifically, we make use of Turán’s theorem, a seminal result in extremal combinatorics, to reason about an adversary’s optimal strategy for disrupting an algorithm of a given duration. We then show how to generalize our upper bound to cope with an adversary that can simultaneously disrupt t < c channels. Our generalization makes use of selectors: a combinatorial tool that guarantees that any subset of processes will be “selected ” by some set in the selector. We prove this generalized algorithm optimal if a maximum number of values is to be gossiped. We conclude by extending our algorithm to tolerate traditional Byzantine corruption faults.

Abstract—Many applications that make use of sensor networks require secure communication. Because asymmetric-key solutions are difficult to implement in such a resource-constrained environment, symmetric-key methods coupled with a priori key distribution schemes have been proposed to achieve the goals of data secrecy and integrity. These approaches typically assume that all nodes are similar in terms of capabilities and, hence, deploy the same number of keys in all sensors in a network to provide the aforementioned protections. In this paper, we demonstrate that a probabilistic unbalanced distribution of keys throughout the network that leverages the existence of a small percentage of more capable sensor nodes can not only provide an equal level of security, but also reduce the consequences of node compromise. To fully characterize the effects of the unbalanced key management system, we design, implement, and measure the performance of a complementary suite of key establishment protocols known as LIGER. Using their predeployed keys, nodes operating in isolation from external networks can securely and efficiently establish keys with each other. Should resources such as a backhaul link to a key distribution center (KDC) become available, networks implementing LIGER automatically incorporate and benefit from such facilities. Detailed experiments demonstrate that the unbalanced distribution in combination with the multimodal LIGER suite offers a robust and practical solution to the security needs in sensor networks. Index Terms—Heterogeneous sensor networks, probabilistic key management, probabilistic authentication, hybrid network security. 1

Abstract—We analyze the performance limits of data dissemination with multi-channel, single radio sensors. We formulate the problem of minimizing the average delay of data dissemination as a stochastic shortest path problem and show that, for an arbitrary topology network, an optimal control policy can be found in a finite number of steps, using value iteration or Dijsktra’s algorithm. However, the computational complexity of this solution is generally prohibitive. We thus focus on two special classes of network topologies of practical interest, namely single-hop clusters and multi-hop cluster trees. For these topologies, we derive the structure of policies that achieve an average delay within a factor 1+ɛ of the optimal average delay, in networks with large number of nodes. Through simulation, we show that these policies perform close to optimal even for networks with small and moderate numbers of nodes. Our analysis and simulations reveal that multichannel data dissemination policies lead to a drastic reduction in the average delay, up to a factor as large as the total number of channels available, even though each node can communicate over only one channel at any point of time. Finally, we present the foundations of a methodology, based on extreme value theory, allowing the implementation of our near-optimal dissemination policies with minimal overhead. I.

Abstract — It is usual to quantify the performance of communication networks in terms of achievable throughput or delay. However, as a result of the significant recent interest in safety-critical application scenarios for wireless networking, security and reliability concerns are gradually emerging at the forefront of wireless networking research. In light of this, it is increasingly crucial to consider secure communication capacity or delay as primary performance measures, and evolve theoretical frameworks that can allow for quantification of the trade-off between security and performance. In this paper, we argue for the need for comprehensive effort in this direction, and present an illustrative example of the same by describing asymptotic secure-capacity results for randomly deployed wireless network where each node is preloaded with a random subset of keys. I.

We analyze the performance limits of data dissemination with multi-channel, single radio sensors under random packet loss. We formulate the problem of minimizing the average delay of data dissemination as a stochastic shortest path problem and show that, for an arbitrary topology network, an optimal control policy can be found in a finite number of steps, using value iteration or Dijkstra’s algorithm. However, the computational complexity of this solution is generally prohibitive. We thus focus on two special classes of network topologies of practical interest, namely single-hop clusters and multi-hop cluster chains. For these topologies, we derive the structure of policies that achieve an asymptotically optimal average delay, in networks with large number of nodes. Our analysis reveals that a single radio in each node suffices to achieve performance gain directly proportional to the total number of channels available. Through simulation, we show that the derived policies perform close to optimal even for networks with small and moderate numbers of nodes and can be implemented with limited overhead.

Many wireless sensor network (WSN) applications demand secure communications. The random key pre-distribution (RKP) protocol has been well accepted in achieving secure communications in WSNs. A host of key management protocols have been proposed based on the RKP protocol. However, due to the randomness in key distribution and strong constraint in key path construction, the RKP based protocols can only be applied in highly dense networks, which are not always feasible in practice. In this paper, we propose a methodology called network decoupling to address this problem. With this methodology, a wireless sensor network is decoupled into a logical key-sharing network and a physical neighborhood network, which significantly releases the constraint in key path construction of RKP protocol. We design two new key management protocols, i.e., RKP-DE and RKP-DEA, as well as a set of link and path dependency elimination rules in decoupled sensor networks. Our analytical and simulation data demonstrate the performance enhancement of our solutions from the perspective of connectivity and resilience, and its applicability in non-highly dense sensor networks.

Abstract — Secure communications are highly demanded by many wireless sensor network (WSN) applications. The random key pre-distribution (¢¤£¦ ¥ ) scheme has become well accepted to achieve secure communications in WSNs. However, due to its randomness in key distribution and strong constraint in key path construction, the ¢¤£¦ ¥ scheme can only be applied in highly dense networks, which are not always feasible in practice. In this paper, we propose a methodology called network decoupling to solve this problem. With this methodology, a wireless sensor network is decoupled into a logical key-sharing network and a physical neighborhood network, which significantly releases the constraint in key path construction of ¢¤£¦ ¥ scheme. We design a secure neighbor establishment protocol ¢¤£¦ ¥ (called §©¨) as well as a set of link and path dependency elimination rules in decoupled wireless sensor networks. Our analytical and simulation data demonstrate the performance enhancement of our solution and its applicability in non-highly dense wireless sensor networks. I.

Abstract—Secure wireless communications typically rely on secret keys, which are hard to establish in a mobile setting without a key management infrastructure. In this paper, we propose a channel hopping protocol that lets two stations agree on a secret key over an open wireless channel and without use of any pre-existing key. It is secure against an adversary with typical consumer radio hardware that only allows receiving on a single (or a few) channel at a time. Theoretical analysis and simulation results indicate that this approach can generate a 128-bit key in 0.3 seconds. This is significantly faster than prior techniques that extract key material from the wireless channel. I.