Unkeyed DEPIR ⇒ PK-DEPIR

Fully-black-box reduction · standard model · folklore

Statement

Every unkeyed DEPIR scheme is, unchanged, a public-key DEPIR scheme: its deterministic $\mathsf{Setup}$ is key generation outputting $(k,k^{\prime })=(\perp ,\perp )$ followed by $\mathsf{Prep}(1^{\lambda },\perp ,DB):=\mathsf{Setup}(1^{\lambda },DB)$, and with $k=\perp$ the public-key privacy game is the unkeyed one — folklore.