Hopper: Bounded-Memory Collaborative Debiasing for Byzantine-Tolerant Peer Sampling
Researchers propose Hopper, a bounded-memory debiasing protocol that protects Byzantine-tolerant peer sampling from delayed balanced attacks defeating cumulative counters.
The paper shows that frequency-aware debiasing based on cumulative per-identifier counts fails under a delayed balanced attack, where a long benign prefix masks a subsequent adversarial frequency shift. Hopper introduces a bounded-memory debiasing protocol using BitMatcher as the stream estimator, plus BMDecay, a saturation-triggered decay and reconstruction mechanism keeping frequency signal fresh. It also supports authenticated fingerprint-aware trusted collaboration with role-specific debiasing. Experiments show faster recovery from delayed attacks and debiasing comparable to non-debiasing baselines under a fixed memory budget, with a re-identification trade-off at high trusted-node densities.