A Multi-hop Multi-source Algebraic Watchdog

TL;DR

This paper extends an algebraic watchdog scheme to multi-hop, multi-source wireless networks, enabling nodes to probabilistically detect malicious behavior and establish trust in coded systems through a graphical model and algorithms like Viterbi.

Contribution

It generalizes the algebraic watchdog to complex networks and introduces a distributed trust protocol using a trellis graphical model for malicious node detection.

Findings

The scheme can detect adversarial nodes with high probability in multi-hop networks.

Analytical results show reliable communication is possible if min-cut isn't dominated by Byzantine adversaries.

Preliminary simulations support the analytical model's effectiveness.

Abstract

In our previous work "An Algebraic Watchdog for Wireless Network Coding", we proposed a new scheme in which nodes can detect malicious behaviors probabilistically, police their downstream neighbors locally using overheard messages; thus, provide a secure global "self-checking network". As the first building block of such a system, we focused on a two-hop network, and presented a graphical model to understand the inference process by which nodes police their downstream neighbors and to compute the probabilities of misdetection and false detection. In this paper, we extend the Algebraic Watchdog to a more general network setting, and propose a protocol in which we can establish "trust" in coded systems in a distributed manner. We develop a graphical model to detect the presence of an adversarial node downstream within a general two-hop network. The structure of the graphical model (a trellis) lends itself to well-known algorithms, such as Viterbi algorithm, that can compute the probabilities of misdetection and false detection. Using this as a building block, we generalize our scheme to multi-hop networks. We show analytically that as long as the min-cut is not dominated by the Byzantine adversaries, upstream nodes can monitor downstream neighbors and allow reliable communication with certain probability. Finally, we present preliminary simulation results that support our analysis.