A warden can fingerprint the specific covert destination a Telex user is visiting by comparing observed latency distributions against a pre-built database of covert-destination latencies. With an intelligently filtered database of only 10 distributions (K-S inter-entry threshold 0.8), the AUC is 0.868, and with approximately 12 collected samples the false positive rate drops below 10%. Larger databases (size 50) degrade to AUC 0.537 due to distribution similarity, but threshold-based filtering restores substantial discriminative power.
From 2012-schuchard-routing — Routing Around Decoys
· §5.3, Figures 7, 9
· 2012
· Computer and Communications Security
Implications
Covert-destination anonymity — not just usage unobservability — must be an explicit design goal; decoy routing schemes should introduce artificial latency noise sufficient to collapse inter-destination K-S discrimination, or route all covert traffic through a shared anonymizing pool before the final hop.
Because only ~12 RTT samples suffice for reliable fingerprinting, even short-lived sessions are vulnerable; session-level latency shaping (not just per-packet) is required.