Poker Face Defense: Countering Passive Circuit Fingerprinting Adversaries in Tor Hidden Services

Tor is a widely used tool that offers anonymity and privacy to its users while handling general internet traffic and providing hidden services (HS) for secure content access. Volunteer-operated virtual tunnels in a multi-hop connectivity model enable Tor’s hidden services to ensure anonymity for users, content providers, and servers. However, recent studies have shown that patterns in the connection process of Tor HS can compromise user anonymity and expose content despite encryption through website fingerprinting. This level of exposure can be dangerous for Tor users, given the sensitivity of the content it handles. Therefore, this study proposes a new approach to address the patterns that threaten Tor user anonymity. The proposed method, the Poker Face Algorithm, modifies Tor’s hidden service connectivity to eliminate distinguishable characteristics and make the connection process between the user and the hidden server indistinguishable. By effectively altering the way clients and hidden services connect to Tor, the Poker Face Algorithm successfully removes identifiable patterns that can compromise identity by leaving a connectivity pattern through tracing packets exchanged during connectivity.