CenTor's anonymity scoring function quantifies the privacy cost of geographic shadow selection using six parameters (client density, AS-level and country-level entropy, relay density, exit density, guard density). Prior work establishes that reducing the client anonymity set by 20x—retaining at least 5% of total Tor users—still provides strong anonymity; accordingly, CenTor recommends minimum thresholds of CD, EL, EC ≥ 0.05 and RD, ED ≥ 0.2 for safe shadow operation.
Circumvention tools that restrict relay selection geographically (e.g., country-restricted circuits for latency) should quantify anonymity loss against a 20x anonymity-set reduction threshold before deployment, not just measure performance gains.
Western Europe and Eurasia pass all minimum thresholds (αCenTor > 0; Germany alone hosts 978 entry nodes) while providing strong CDN locality—these regions are the best candidates for geo-aware relay clustering in latency-sensitive Tor-based circumvention infrastructure.