Anonymous Networking amidst Eavesdroppers

The problem of security against timing based traffic analysis in wireless networks is considered in this work. An analytical measure of anonymity in eavesdropped networks is proposed using the information theoretic concept of equivocation. For a physical layer with orthogonal transmitter directed signaling, scheduling and relaying techniques are designed to maximize achievable network performance for any given level of anonymity. The network performance is measured by the achievable relay rates from the sources to destinations under latency and medium access constraints. In particular, analytical results are presented for two scenarios: For a two-hop network with maximum anonymity, achievable rate regions for a general m x 1 relay are characterized when nodes generate independent Poisson transmission schedules. The rate regions are presented for both strict and average delay constraints on traffic flow through the relay. For a multihop network with an arbitrary anonymity requirement, the problem of maximizing the sum-rate of flows (network throughput) is considered. A selective independent scheduling strategy is designed for this purpose, and using the analytical results for the two-hop network, the achievable throughput is characterized as a function of the anonymity level. The throughput-anonymity relation for the proposed strategy is shown to be equivalent to an information theoretic rate-distortion function.

💡 Research Summary

The paper tackles the problem of protecting wireless networks from timing‑based traffic analysis, where an eavesdropper can infer the identity of communicating parties simply by observing packet transmission times. Instead of relying on traditional cryptographic padding or constant‑rate transmission, the authors adopt an information‑theoretic notion of anonymity: the equivocation (conditional entropy) of the source identities given the observed timing trace. The physical layer is assumed to support orthogonal, directionally‑focused signaling (e.g., beamforming), allowing multiple transmitters to operate simultaneously without mutual interference. Within this setting, the authors design scheduling and relaying policies that maximize the achievable network performance for any prescribed level of anonymity.

Two main scenarios are examined.

1. Two‑hop network with maximum anonymity – The network consists of m independent sources, a single relay (an m × 1 configuration), and a destination. Each source generates transmission attempts according to an independent Poisson process. “Maximum anonymity” means the eavesdropper’s observation provides no information about which source generated a given packet (the equivocation equals the source entropy). Under this constraint the authors derive the complete achievable rate region for the relay, considering two types of latency constraints:

   • Strict delay – Every packet must be forwarded by the relay within a hard deadline Δ after arrival. By modeling the relay as an M/D/1 queue with a deadline, the stability condition becomes λ_total < μ·(1 − e^{−μΔ}), where λ_total is the sum of source Poisson rates and μ is the relay service rate. The resulting rate region is a convex polytope whose vertices correspond to priority‑based service orders.

   • Average delay – Only the mean waiting time is bounded (E