Monte Carlo simulations across four EoL exclusion rounds (2021–2023) show that natural relay churn is the dominant driver of Tor client anonymity loss, with EoL exclusions giving AS and IXP adversaries an advantage equivalent to only ~4 days (AS adversary) or ~9 days (relay adversary) of the network running without exclusion. In the 2021 exclusion event, up to ~1% of additional clients were compromised; by 2023 this figure dropped to ~0.30%, attributed to improved operator update discipline and Tor Project communications.

The Tor EoL enforcement policy reduced the excluded relays' consensus-weight share from 13.25% in the first 2019 exclusion to roughly 7% of advertised bandwidth in the 2023 exclusion, demonstrating that iterative enforcement combined with improved operator communication (email, mailing list, social media) steadily reduces version fragmentation in a volunteer relay network over a 4-year horizon.

§5.1, §2.2 evaluation

Across four analyzed exclusion rounds, a minority of rejected relays consistently accounted for over 50% of the security contribution (measured by individual path-compromise protection against AS, IXP, and relay adversaries) provided by all excluded relays combined, enabling selective prioritization of relay update outreach.

§6, Abstract evaluation

Default OS package repositories (Debian, Ubuntu LTS, FreeBSD quarterly) routinely ship Tor versions that lag behind the Tor Project's minimum accepted version, causing relays installed from default repos to be excluded immediately or within months of deployment. Debian LTS typically ships a Tor version that becomes excluded toward the end of the OS lifetime; Ubuntu LTS does not generally ship an LTS Tor version at all.

§3.3.2, Figure 3 deployment

In the April 2024 Tor exclusion event, 440 of 7,765 relays were excluded; only 68 (15%) returned with the same fingerprint within one month, while 372 (85%) never returned. Of the 553 relays running to-be-excluded versions one month before the deadline, only 75 updated in time.

§3.3.4, Figure 4 evaluation

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

In the 30 November 2025 Onionoo snapshot, approximately 75% of both guard and middle relay selection-probability mass lies within Fourteen-Eyes jurisdictions, with Germany, the United States, and the Netherlands hosting the largest shares. Because path selection is bandwidth-weighted, a state-level adversary from one of these jurisdictions is statistically likely to have ISP-level visibility at most relays a target introduction circuit passes through.

2026-constantinides-cost-stability-deanonymizing Appendix D, Fig. 7 flow-correlation

An adaptive intersection attack exploiting the 18–24h fixed lifetime of Tor onion-service introduction circuits reconstructed the complete four-hop introduction circuit in all nine live-network experiments. The median reconstruction required 260 iterations with an estimated median wall-clock time of 2.24h (12% of the 18h circuit lifetime) when per-relay visibility cost v=0; the slowest run completed in 6.63h (37% of 18h).

2026-constantinides-cost-stability-deanonymizing §4.2, Table 1 flow-correlationtraffic-shape

A persistent 'tail' of recurring candidates — not the early phase — dominates convergence cost and introduces high variance: three Vanguard stages at identical consensus weight 1200 converged at iterations 12, 142, and 251. In 13 of 36 stages, the intersection held ≥3 candidates at the penultimate iteration and collapsed to a singleton in one step, suggesting the tail is caused by persistent third-party guard/vanguard traffic rather than random noise.

2026-constantinides-cost-stability-deanonymizing §4.2, Table 2 flow-correlationtraffic-shape

Across all 36 stages in the nine end-to-end experiments, the median iteration at which the running intersection shrank to ≤10 candidates was 3, and 64% of stages reached this threshold within 5 iterations. Per-stage candidate sets shrank by 72–87% after the first intersection and by 85–96% by the third iteration, driven by the short (~0.5–1.8s) observation windows that prevent unrelated circuits from injecting persistent false candidates.

2026-constantinides-cost-stability-deanonymizing §4.2 flow-correlationtraffic-shape

Periodically rebuilding only the internal service-side path of the introduction circuit (entry guard → vanguard → middle relay) approximately every 10 minutes — while keeping the publicly advertised Introduction Point fixed — limits evidence accumulation to one rebuild interval without requiring a descriptor update. Under this mitigation the effective circuit lifetime visible to an intersection attacker drops from 18–24h to ~10 min, matching ordinary Tor circuit lifetimes.

2026-constantinides-cost-stability-deanonymizing §5 flow-correlation