DNS Privacy Leaking Mitigation and Energy Costs: Measuring the Impact of Adding Dummy Queries on Encrypted DNS...

The Domain Name System (DNS) was originally designed without privacy mechanisms. Encrypted variants such as DNS over TLS (DoT), DNS over HTTPS (DoH), DNS over HTTP/3 (DoH/3), and DNS over QUIC (DoQ) protect the content of the queries, but the resolver and any network observer with access to the traffic metadata can still profile the user. Client-side defenses counter this by adding dummy queries to the real DNS traffic of the device. On a smartphone, the battery cost of such a defense has not been characterized. We evaluate the energy cost of adding dummy queries on an unmodified Android device using the BatteryStats subsystem. Since the dummy queries must be sent over the protocols the device already uses, we measure this cost for the five DNS protocols in use (Do53, DoT, DoH, DoH/3, and DoQ) and four public resolvers (Google DNS, Cloudflare, Quad9, and AdGuard DNS), at both the application and system-resolver levels. Our results show that the cost of the countermeasure depends on the protocol and resolver used, on the number of dummy queries added, and on their scheduling: sending them as a single burst rather than periodically reduces the energy cost for the same privacy gain.