Byzantine Attacks in RIS-Enhanced Cooperative Spectrum Sensing: A Decision Fusion Perspective

TL;DR

The paper investigates Byzantine (SSDF) attacks in RIS-enhanced cooperative spectrum sensing for mobile cognitive radio networks under hard decision fusion. It develops channel- and attack-aware fusion rules and derives optimal attack strategies for both small-scale and large-scale Byzantines, showing that attackers can maximize disruption without requiring full global instantaneous CSI, with the attack impact governed primarily by the Byzantine fraction α. A key finding is the unifying framework: when α(P_{0,1}+P_{1,0})=1 large-scale attacks can blind the fusion center, while for α≤0.5 AF/π-optimized flips minimize the decision statistic magnitude and degrade performance; for α>0.5 RD-like strategies can effectively collapse information. The work also demonstrates robustness constraints are relaxed regarding ICSI and fusion rule knowledge, and validates the theory through extensive simulations across mobility, RIS sizes, and relay configurations. These insights inform secure design and defense strategies for RIS-enabled CSS in dynamic, multi-hop mobile CRNs.

Abstract

From the perspective of hard decision fusion, we investigate Byzantine attacks in Reconfigurable Intelligent Surface (RIS)-enhanced and decode-and-forward relay-assisted Cooperative Spectrum Sensing (CSS) for mobile Cognitive Radio Networks (CRNs) in this paper. Specially, a RIS-enhanced and decode-and-forward relay-assisted CSS configuration is first constructed under dynamic channel scenarios due to user mobility. Subsequently, the channel- and attack-aware hard decision fusion rules are developed, and the optimal channel-aware Byzantine attack strategies are then developed under both small-scale and large-scale attacking scenarios. The corresponding results depict that the optimal attack strategy does not require any a prior knowledge of the global instantaneous Channel State Information (ICSI) (e.g. false alarm probability and detection probability of all the secondary users), although perfect acquisition of ICSI is clearly always not affordable from the attacker perspective, which is further exacerbated by the RIS and decode-and-forward relays involved in CSS and the potential high mobility of secondary users that leads to fast fading channels. Furthermore, our counterintuitive results also indicate that, regardless of the attacker's awareness of the decision fusion rule, the optimal Byzantine attack can be achieved through a unifying framework, the explicit attack strategy may be not unique, and the attacking effectiveness is primarily determined by the fraction of the Byzantine nodes rather than the channel dynamics. That is, to make the channel-aware approach more practical, the challenge that the heavy reliance on the global ICSI and decision fusion rule in obtaining the Byzantine attacks is successfully relaxed. Finally, we empirically validate our theoretical analysis through extensive simulations across a wide range of attacking scenarios.

Figures (12)

• Figure 1: RIS Enhanced Mobile CRNs under Byzantine Attacks.
• Figure 2: System Model with Byzantine Attacks.
• Figure 3: The BER Performance of Optimal Fusion Rule under Small-Scale Attacks.
• Figure 4: The Magnitude of LLR for Optimal Fusion Rules under Small-scale Attacks.
• Figure 5: The BER performance of Optimal Fusion Rule under different Attack Strengths and Numbers of SUs Antennas.