Packet timings are a distinct detection vector for circumvention tools beyond payload content and packet lengths, as demonstrated by Wails et al. 2024. Prior FEP-specific shaping work (Fenske et al.) addressed packet lengths but explicitly left timing shaping for future work, leaving a known gap in detection resistance.

Shaperd's adaptive blocking-detection mode can integrate with external blockage-detection tools (e.g., Troll Patrol) to detect when a constraint set is no longer effective and automatically switch to an alternate constraint set, changing packet patterns to restore connectivity without user intervention.

Appendix A defense

The GFW detects fully encrypted protocols using ad-hoc rules including the percentage of printable ASCII characters per packet (threshold: over 50%) and the observation that FEP entropy is considerably higher than normal encrypted TLS traffic. These rules are subject to frequent changes, making rigid FEP designs unable to adapt.

§1 detection

Shaperd's proof-of-concept prototype (~1000 lines of Go) introduces a minimal 4.1% throughput overhead for a single entropy constraint; the first additional constraint added 5.1% overhead and the second added 5.5%, with total overhead scaling with constraint count and rigor.

§2 evaluation

Shaperd introduces a constraint-agnostic traffic shaping system that operates on both packet content and timing in real time, designed for drop-in integration with any existing FEP. The system uses a four-component constraint definition (function, value, comparison operator, target packets) capable of expressing any rule based on a computable deterministic function over packet contents.

§2 defense

Internal Geedge documents confirm active contracts to deploy GFW-derived censorship and surveillance infrastructure in Myanmar, Pakistan, Ethiopia, Kazakhstan, and at least one additional unidentified country under the Belt and Road framework, in addition to domestic deployments in Xinjiang, Jiangsu, and Fujian. The exported product (the Tiangou Secure Gateway / TSG line) is not a stripped-down export variant — leaked TSG documentation shows DPI, active-probing, ML classifiers, and granular per-region traffic control rules that mirror the domestic GFW capability set.

2025-geedge-mesa-leak §5, §6 dpiactive-probingml-classifiersni-blockingdns-poisoningfully-encrypted-detecttraffic-shape

InterSecLab's 76-page analysis of the Geedge/MESA leak (based on nine months of indexing and translating >100,000 documents) characterizes the Tiangou Secure Gateway (TSG) product line as a commercially deployable detection stack that combines deep packet inspection, real-time mobile subscriber monitoring, active probing, ML-based traffic classifiers, and granular per-region rule sets. TSG is not a research prototype — leaked documentation includes deployment timelines and client government interactions for Kazakhstan, Ethiopia, Pakistan, Myanmar, and one unnamed country, with censorship rules explicitly tailored to each region.

2025-interseclab-internet-coup §3–§5 (InterSecLab report) dpiactive-probingml-classifiersni-blockingip-blockingtraffic-shapefully-encrypted-detect

Censorship classifiers and traffic analysis attacks consistently exploit the initial seconds of a proxy connection, where packet-size, inter-arrival-time, and burst features are maximally discriminative. Cited work demonstrates that website fingerprinting classifiers trained solely on the first few seconds of Tor traffic achieve high accuracy, and real-world GFW detection of fully-encrypted protocols also targets early-connection bytes.

2025-pereira-extended §1 traffic-shapewebsite-fingerprintml-classifierdpifully-encrypted-detect

Custom CCAs that deviate from standard TCP/QUIC congestion response fundamentally contradict the core circumvention principle of traffic indistinguishability: by failing to back off under congestion signals, they produce traffic patterns that diverge from the vast majority of Internet flows that censors value, eliminating the collateral-damage protection that makes circumvention tools hard to block wholesale.

2025-wang-custom §1, §6 traffic-shapefully-encrypted-detect

WATER (WebAssembly Transport Executables at Runtime) defines a pluggable-transport architecture in which the transport logic is compiled to a WASM module that is loaded and executed at runtime by a thin Go host process. This separates the stable host ABI (dial, accept, read, write) from the rapidly-evolving transport logic, allowing new or updated transports to be delivered as small WASM binaries without recompiling or redeploying the host application.

2017-frolov-water-pluggable §2–3 dpifully-encrypted-detecttraffic-shape

WATER (WebAssembly Transport Executables Runtime) separates transport logic from the host application by compiling it to a WASM module (WATM) that is distributed and loaded independently at runtime. Deploying a new or updated circumvention technique requires only distributing the new WATM binary and optional configuration — no change to the host application and no app-store update cycle is required.

2024-chi-just §1, §3 dpifully-encrypted-detecttraffic-shape