  Epidemics like the recent COVID-19 require proactive contact tracing and
epidemiological analysis to predict and subsequently contain infection
transmissions. The proactive measures require large scale data collection,
which simultaneously raise concerns regarding users' privacy. Digital contact
tracing systems developed in response to COVID-19 either collected extensive
data for effective analytics at the cost of users' privacy or collected minimal
data for the sake of user privacy but were ineffective in predicting and
mitigating the epidemic risks. We present Silmarillion--in preparation for
future epidemics--a system that reconciles user's privacy with rich data
collection for higher utility. In Silmarillion, user devices record Bluetooth
encounters with beacons installed in strategic locations. The beacons further
enrich the encounters with geo-location, location type, and environment
conditions at the beacon installation site. This enriched information enables
detailed scientific analysis of disease parameters as well as more accurate
personalized exposure risk notification. At the same time, Silmarillion
provides privacy to all participants and non-participants at the same level as
that guaranteed in digital and manual contact tracing. We describe the design
of Silmarillion and its communication protocols that ensure user privacy and
data security. We also evaluate a prototype of Silmarillion built using low-end
IoT boards, showing that the power consumption and user latencies are
adequately low for a practical deployment. Finally, we briefly report on a
small-scale deployment within a university building as a proof-of-concept.
