Module oprf::coprf

Extension E. Convertible PRF (coPRF)

This part of the document describes an extension to the OPRF protocol called convertible PRF (coPRF) introduced in [Lehmann].

A coPRF is a protocol for blind evaluation of a PRF between three parties, as opposed to the two parties in the regular OPRF setting. A requester wishes the PRF to be evaluated blindly under the key held by the evaluator. Unlike in the two-party OPRF setting, the blinded evaluation result is not returned to the requester, but to a third party, the receiver. Only the receiver can unblind the evaluation result and thus receive the PRF output.

CoPRFs further provide the possiblity of converting PRF outputs, both in blinded and unblinded form, from one PRF key to another.

Modules

• coprf_online
  E.2. CoPRF Online Protocol
• coprf_setup
  E.1. CoPRF Setup