2025-farrell-ech-trial-report

ECH Trial Report

Stephen Farrell, Sukhbir Singh · Wikimedia technical report · 2025

Abstract

Documents a small-scale trial deployment of Encrypted Client Hello (ECH) at Wikimedia Foundation in collaboration with the DEfO project. Evaluates whether ECH deployment affects service availability and measures ECH adoption across different client types, operating systems, and regions. Finds that ECH does not impact service availability and works as expected for ECH-capable clients.

Team notes

Auto-ingested via corpus-crawl. Tags proposed by Claude Haiku 4.5; review and tighten before relying. Critical for understanding real-world ECH adoption barriers and deployment lessons; directly informs circumvention strategies against SNI-based blocking in China, Iran, Russia, and other state censors.

Tags

censors: generic
techniques: sni-blocking
defenses: ech-esni
method: controlled-deployment

findings extracted from this paper

Apple iOS devices showed zero ECH successes across all tested versions from iOS 9.1 through iOS 18.5 (totaling 383 accesses), and Mac OS systems showed sparse ECH support limited to Firefox on older macOS and Chrome on macOS 10.15.7. A single GREASEd access from iPadOS/18.0 (Mobile Safari) was the only signal of any Apple ECH awareness.

§6.3, Table 5; §6.5 evaluation sni-blocking generic
Even ECH-capable browsers frequently GREASE rather than attempt real ECH, with Firefox/138 succeeding only 50% of the time (164/325), Chrome/136 only 25% (42/167), and Chrome Mobile/136 only 24% (29/121). Firefox/139 performed better at 83% real ECH success (351/423), suggesting browser DNS handling of HTTPS RRs remains a significant barrier to ECH efficacy. GREASE sends a fake ECH extension that does not hide the inner SNI, so it provides no censorship resistance despite making the client appear ECH-aware.

§6.4, Table 8 evaluation sni-blockingtls-fingerprint generic
In a 41-day real-world ECH trial (2025-05-01 to 2025-06-11) across 14 server instances in 7 global data centers, 64% of accesses came from ECH-aware clients (success or GREASE) while 36% did not attempt ECH at all. Of 4,074 total log events, 1,660 were ECH successes, 825 were GREASE, and 1,589 were not-tried, indicating that today roughly 41% of traffic benefits from full ECH privacy protection. The trial found no measurable service disruption from enabling ECH.

§6.1, Table 3 evaluation sni-blocking generic
Wikimedia's preferred deployment mode — ECH split-mode, which would use a third-party front-end's IP addresses to bypass IP-level blocking of Wikimedia's own address space — could not be trialed because no suitable front-end partner was found. Potential operators declined due to concerns about traffic volume, risk of inheriting Wikimedia's blocked reputation, or lack of a compatible business model.

§2 deployment ip-blocking generic
The DEfO project backported ECH support to nginx 1.22.1 (Debian bookworm's shipped version) and deployed it at 14 instances across 7 Wikimedia data centers with no service disruption over 41 days. The primary operational barrier was institutional review process for custom-built binaries and the novel HTTPS RR DNS record type, adding only a few days to the deployment timeline.

§3, §4, §7 deployment sni-blocking generic
Across all 7 global data centers (EU, USA, Singapore, Brazil), every data center recorded ECH successes with no observed evidence of regional ECH blocking or interference. ECH-aware client percentages varied by region — EU 75%, North America 63%, Asia 49%, South America 46% — but this was attributed to browser version distribution rather than censorship. The trial spanned 14 geographically distributed PoPs.

§6.2, §6.5, Table 4 evaluation sni-blocking generic