CRCI: Local Reputation-Based Fault Isolation for Ad-Hoc Gossip Communication

Infrastructure failure during disasters eliminates the connectivity upon which emergency coordination depends. Ad-hoc mesh networking addresses physical-layer reachability but provides limited protection against Byzantine faults: nodes that inject false reports, suppress messages, or broadcast inconsistent state to partition the network. This paper presents CRCI (Crisis Response Communication Infrastructure), a peer-to-peer mesh protocol implemented in Rust that integrates local misbehaving-peer isolation directly into the gossip layer. Each node maintains a local, event-triggered reputation score for every peer, derived from authenticated and protocol-verifiable behavioral evidence, specifically the transmission of invalid signatures or explicitly malicious direct message replays. The system enforces local reputation-based peer eviction using a deterministic three-strike threshold rule, independently isolating malicious nodes without requiring synchronized voting rounds or stable membership. Across 50 runs per condition (100 runs total) on a loopback testbed, CRCI detects and evicts a replaying attacker after exactly three strikes without requiring voting rounds, achieving 50/50 survivability for honest peers that send fresh sequence numbers under deterministic reordering workloads. However, we also demonstrate that an adaptive attacker can evade isolation by pacing malicious replays to exploit reputation recovery. These results provide empirical evidence that the proposed reputation-based fault-isolation mechanism can operate through fully local decisions, supporting the feasibility of local fault isolation as a component of decentralized crisis communication.