Telex embeds steganographic tags in TLS ClientHello nonces using elliptic-curve Diffie-Hellman, placing proxy stations at ISP level on paths between the censor's network and popular uncensored destinations. Because the cover destinations are ordinary popular HTTPS websites, the censor cannot block Telex without simultaneously blocking a large class of legitimate TLS traffic — converting the censor's own reluctance to over-block into an unblockability guarantee.

On a single 2.93 GHz Intel Core 2 Duo CPU core, the Telex elliptic-curve tagging scheme achieves approximately 5,482 tag generations per second and 11,074 tag verifications per second across 10 trials of 100,000 tags each (standard deviations of 0.016 s and 0.0083 s respectively). Tag verification is therefore unlikely to be a throughput bottleneck in a deployed Telex station.

§8.2 evaluation

A PlanetLab node in Beijing successfully loaded all 100 Alexa top-100 websites through a prototype Telex station at the University of Michigan; without Telex, 17 of the 100 sites were blocked (including facebook.com, youtube.com, blogspot.com, and twitter.com from the top 10), using forged RST packets, false DNS results, and destination IP blackholes. The median latency overhead for routing through Telex was approximately 60% for the 83 unblocked sites.

§8.4 evaluation

Telex prevents tag replay attacks by seeding the client's TLS key exchange randomness (e.g., the Diffie-Hellman exponent) with the shared secret ksh derived from the steganographic tag. The TLS Finished message must then be freshly encrypted with the newly negotiated master secret, implicitly proving knowledge of ksh. An adversary replaying a captured ClientHello nonce without knowing ksh cannot produce a valid Finished message, causing the server to terminate the connection.

§6.2 defense

The paper identifies two unresolved fingerprinting surfaces: (1) traffic-shape analysis of packet sizes and inter-arrival times could distinguish Telex flows from normal TLS, and (2) the prototype exhibits detectable deviations from real servers at the IP layer (stale IP ID fields), TCP layer (incorrect congestion windows detectable by early acknowledgements), and TLS layer (different compression methods and cipher-suite extensions). Convincingly mimicking a diverse population of TCP/TLS server implementations is flagged as requiring substantial engineering effort.

§9 detection

The June 2025 Iran shutdown—carried out during the Iran-Israel war beginning ~June 19—did not use BGP route withdrawals as in 2019. Instead, authorities applied service-level restrictions at the national border: DNS poisoning of foreign destinations, protocol whitelisting permitting only pre-approved domestic services, and DPI to block circumvention-tool traffic. Iran's international traffic fell roughly 90% while the country's BGP routes remained advertised, making the shutdown invisible to BGP-based monitoring systems. OONI measurement volume, which totalled 121,333 in June 2025, collapsed to under 200 submissions on June 19-20.

2025-iran-shutdown-measurement Executive Summary / §2 dpidns-poisoningport-blockingip-blocking

Article 19 documents that Iran's National Information Network (NIN / SHOMA) was designed with explicit reference to China's Great Firewall as a model, with institutional mirroring: Iran's Supreme Council of Cyberspace parallels China's Cyberspace Administration of China, and both governments share a "cyber sovereignty" doctrine used to justify domestic content controls and cross-border technology transfer. The report frames Iran's filtering infrastructure as deliberately architected to replicate GFW capabilities, not as an independently developed system.

2026-article19-tightening-the-net §2, §3 dpisni-blockingdns-poisoningip-blockingbgp-hijackthrottling

The GNL reveals that Geedge actively maintains dedicated VPN-infrastructure tracking datasets. The China-specific component includes 7,016 domains in a "vpn-finder-plugins" repository (mesalab_git/intelligence-learning-engine), 4,810 NordVPN server domains, and a Pakistan-specific file listing 68 Psiphon CDN domains (geedge_docs/TSGEN/.../Psiphon-CDN_20240430.json) dated April 2024. A Myanmar deployment file (M22-VPN List.html, 27 domains) further confirms country-specific VPN blocklists are operationally maintained. The "Appsketch" program reverse-engineers VPN apps to extract domains and IP addresses for blocking.

2026-sheffey-geedge §4.2, Table 3 dpisni-blockingip-blocking

Iran's censorship of refraction-networking proxies (Conjure via Psiphon) is not monolithic: different ISPs independently deploy different techniques and timelines. Over 800 million logged Conjure connections from July 2023–February 2025 across 10+ Iranian ASes show TCI (AS58224, ~33% of traffic) uses packet injection, while MCCI/Hamrah-e Avval (AS197207, ~22%) applies IP-based blocking, and some ASes (Parsonline AS16322, Shatel AS31549) show no proxy blocking at all.

2025-alaraj-iran-refraction §4 rst-injectionip-blockingpacket-injectiondpi

Amnesty International's 102-page investigation identifies a multi-vendor surveillance stack deployed in Pakistan: Chinese DPI (Geedge/MESA-derived), Canadian social-media monitoring (Netsweeper), and Emirati commercial spyware (Pegasus and FinFisher). The system enables deep packet inspection, SNI-based filtering, and traffic-shape classification at national scale, including targeted interception of encrypted messaging apps and VPN traffic.

2025-amnesty-pakistan-shadows §3, §5 dpisni-blockingip-blockingtraffic-shapeml-classifier

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