By reusing keys already held by trusted (non-suspicious) users for ℓ−1 of ℓ subgroups when bisecting the suspicious cohort — issuing only one fresh key per round — the total proxy count drops from O(k log n) to O(k² log n / log log n) in expectation. The information-theoretic lower bound is Ω(k log(n/k) / log(k + log n)), so this bound is tight in n up to a factor of k.

A dynamic binary-tree partitioning algorithm solves the proxy distribution problem with at most k(1 + ⌈log₂(n/k)⌉) total proxy keys: partition n users into k groups in round 1, then halve each compromised group on each compromise event. Each of k adversaries can trigger at most ⌈log₂(n/k)⌉ compromises, bounding total proxy expenditure tightly.

§4 Theorem 3 defense

A simple entropy argument proves the dynamic key distribution problem requires at least Ω(k log(n/k) / log(k + log n)) keys: the algorithm must identify which k of n users are adversaries from at most ℓ log ℓ bits of feedback (ℓ round outcomes each indexing one of ℓ keys), and distinguishing among C(n,k) adversary sets requires log C(n,k) = Ω(k log(n/k)) bits.

§4 Theorem 6 evaluation

The static proxy distribution problem — giving k²-adversarial users keys from m proxies so that all n−k legitimate users retain at least one uncompromised proxy — requires at most O(k² log n) keys and cannot be solved with fewer than Ω(k log(n/k)) keys. This establishes the information-theoretic cost of one-shot proxy distribution against k colluding informants among n users.

§3 Theorem 2 defense

In invitation-based proxy networks (modeled on Psiphon's trust-tree), a single adversary can invite fake accounts as children in the trust tree, multiplying the effective adversary count k and invalidating sublogarithmic key budgets. For k=1 adversary on a trust tree of depth O(log n), an O(log n)-key algorithm exists by keeping the 'suspicious group' always rooted at a subtree boundary; for k>1 this remains an open problem.

§5 Theorem 7 defense

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

Article 19 documents that Iran combines technical filtering with formal coercion of major foreign platforms (including Telegram, Instagram, and WhatsApp) to comply with content removal orders under threat of full blocking. The report notes that Iran's 2022 Women Life Freedom protests accelerated platform blocking when foreign operators refused compliance, demonstrating that the censorship system operates in two modes: coerce-and-allow for compliant platforms, block for non-compliant ones. Domain fronting via these platforms is therefore subject to sudden revocation if political conditions change.

2026-article19-tightening-the-net §6 ip-blockingdns-poisoningthrottling

Brussee measures a systematic pattern of Chinese government websites actively blocking access from outside China (the "reverse Great Firewall"), publishing a CSV dataset of affected domains (available at zenodo.org/records/18172145). The paper frames this outbound geo-blocking as a cybersecurity-motivated practice — Chinese authorities classify foreign access to domestic government infrastructure as an attack surface — distinct from the inbound information control goal of the GFW.

2026-brussee-reverse-great-firewall §3, §5 ip-blockingasn-blackholing

Brussee develops a conceptual framework distinguishing two logics of government geo-blocking: (1) information control (blocking inbound foreign content from domestic users) and (2) data sovereignty / attack-surface reduction (blocking outbound access by foreign actors to domestic systems). Chinese government site blocking of external IPs is motivated primarily by the second logic, creating an asymmetric internet topology where CN citizens cannot reach the outside world, and outside actors cannot probe CN government infrastructure.

2026-brussee-reverse-great-firewall §2, §4 ip-blockingasn-blackholing

ShieldShare demonstrates that an Android application can route all hotspot-client traffic through a VPN tunnel without root access by using a SOCKS5/HTTP/HTTPS proxy layer between the hotspot and the VPN, with per-client traffic accounting and quota management. The system works because Android's native hotspot does not forward VPN routing tables to connected clients; ShieldShare interposes a proxy that handles this. Released as open-source.

2026-edorh-shieldshare §Abstract ip-blocking