  In this work we describe a token-based solution to Contact Tracing via
Distributed Point Functions (DPF) and, more generally, Function Secret Sharing
(FSS). The key idea behind the solution is that FSS natively supports secure
keyword search on raw sets of keywords without a need for processing the
keyword sets via a data structure for set membership. Furthermore, the FSS
functionality enables adding up numerical payloads associated with multiple
matches without additional interaction. These features make FSS an attractive
tool for lightweight privacy-preserving searching on a database of tokens
belonging to infected individuals.
