A deterministic Hidden Markov Model trained on 770,000+ real Synchrophasor samples produces interpacket timing that is statistically indistinguishable from the host protocol: the two-sample Kolmogorov–Smirnov test yields p = 0.21 (threshold 0.05, fail to reject null), and χ² homogeneity p-values for all three timing states are 0.82, 0.37, and 0.15 respectively.

Protocol Proxy uses 'protected static protocols' — UDP-based protocols whose blocking causes severe collateral damage (e.g., Synchrophasor power-grid traffic, NTP) — as cover channels. Because any detection rule that fires on Protocol Proxy traffic also fires on legitimate PMU traffic, censors face a forced trade-off between blocking circumvention and disrupting critical infrastructure.

§3, §5 defense

Observation-based FTE constructs each packet field exclusively from values previously observed in real host-protocol traffic, guaranteeing syntactic equivalence. Wireshark correctly decodes Protocol Proxy-generated packets as valid Synchrophasor frames with correct checksums, and the Phasor Data Concentrator hardware accepts them; any rule blocking Protocol Proxy traffic must therefore also block legitimate PMU packets.

§5.1, §7 defense

The Protocol Proxy achieves an observed goodput of only 182 bps against a 54 Mbps baseline link (>99.99% reduction), well below the theoretical ceiling of 15,477 bps; the gap is attributed to TCP retransmission overhead and the TCP header transiting the proxy. Tor baseline goodput measured at 7.31 Mbps by comparison.

§7, Table 2 evaluation

Static protocols — UDP-based with no application-layer handshake — are immune to stateful protocol analysis that defeated SkypeMorph: without a handshake state machine, a censor cannot flag discrepancies between observed and expected protocol states. This eliminates the detection vector that Houmansadr et al. (2013) exploited to identify SkypeMorph via handshake mismatch.

§3 defense

A three-stage detection pipeline exploiting the "dual-role" behavioral fingerprint of single-IP circumvention relays achieved 23.2% recall (96/414 ground-truth relays) with a 0.18% false-positive rate against 97,651 benign TLS servers, for an overall accuracy of 99.5%. The ground-truth set covered OpenVPN, WireGuard, and SOCKS relays identified in a 17 TB single-day backbone trace (WIDE Project, April 9, 2025).

2026-almutairi-server §3.4, Table 1 traffic-shapedpiflow-correlation

The paper identifies a fundamental architectural vulnerability in single-IP circumvention designs: a relay must generate new observable flows (via DNS or TLS SNI) to reach end services after receiving client connections, creating a detectable server-and-client behavioral contrast. A relay accessing user-facing domains (news, social media) scores high on a Relay Suspicion Score (w=0.9) versus infrastructure domains (w=0.1). The paper argues this host-level signal is censorship-invariant and cannot be concealed by link obfuscation.

2026-almutairi-server §2.4, §4 traffic-shapedpisni-blocking

Simulations extending the ENEM19 game-theory framework show that ephemeral proxy schemes (modeled on Snowflake/Lantern) effectively neutralize both the "optimal" and "aggressive" censors from the original framework. In overprovisioned settings (proxies arriving at 250/step vs. 200 clients/step), even the null censor scenario outperforms either censor in equal-arrival settings. Over 90% of waiting users receive a proxy within 1 time step. The critical variable is not censor sophistication but proxy arrival rate relative to client demand—high proxy churn combined with high arrival rate defeats both enumeration strategies tested.

2026-fares-game §4, Fig 1, Fig 2, Table 1 dpitraffic-shape

The host-profiling censor (passive traffic analysis: count connections per server, block those exceeding a threshold τ within a window w) blocks essentially all circumvention user traffic within 30 time steps for all classifier qualities tested (ρ_TP ∈ {0.9, 0.95, 0.99}), while causing far less collateral damage than zig-zag (never exceeding ~30% innocent server blocking). Snowflake resists this attack well: with w=3, τ=3, over 94.48% of users receive a proxy within 2 steps even with worst-classifier rules, and final unblocked server rates are 91.24–99.04%. The host profiling approach is feasible for passive censors who cannot enumerate the distribution channel.

2026-fares-game §5.2, Table 2, Table 3 traffic-shapeml-classifier

Multi-censor simulations show that single-censor-optimized distribution strategies perform suboptimally in realistic multi-region deployments. When two networks have different censor strategies (e.g., one optimal, one zig-zag), the distributor cannot detect that a proxy is blocked until all censors have blocked it; this leaves clients without reachable proxies despite the proxy appearing "available" from the distributor's view. The authors conclude that "single-censor evaluation does not accurately predict more realistic deployment performance." A zig-zag censor in one region with 0.25 weight caused 44.4% collateral damage while reducing proxy lifetime to a median of 4 steps.

2026-fares-game §6, Table 4 traffic-shapeflow-correlation

The zig-zag traffic analysis attack (confirmed supported in Geedge TSG leak) rapidly enumerates all static proxy pools. With ζ_watch ∈ {4, 6} steps and a best-quality classifier (ρ_TP=0.99, ρ_FP=0.001), almost total proxy enumeration and user blockage occurs well before step 300. Even ζ_watch=2 leaves ~50% of users blocked. Collateral damage is high across all settings when ζ_watch ≥ 4: eventually ~50% of innocent servers are also blocked. However, Snowflake-style ephemeral proxies resist zig-zag effectively: reachability remains above 95% after 360 steps because churn prevents the censor from expanding its known proxy set beyond agents' direct assignments.

2026-fares-game §5.1, Fig 3, Fig 4 traffic-shapeflow-correlation