Sociotechnical Aspects of Tor Relay Rejection
User study and simulations of Tor's relay end-of-life rejection policy find operators favor it; network churn affects anonymity more than EoL exclusions.
The study examines the Tor Project's 2019 end-of-life policy that rejects outdated relays, which constitute a notable fraction of consensus weight. A user study of 26 relay operators found they generally view the policy favorably despite limited awareness, though operational practices occasionally exclude newly installed relays. Historical-data-driven simulations show the policy gives adversaries only marginal advantage, with network churn exerting a more pronounced effect on user anonymity. Analysis of four exclusion rounds shows a minority of rejected relays typically account for over 50% of the security provided by all excluded relays, informing EoL policy recommendations.