Module coprf_setup

E.1. CoPRF Setup

CoPRFs are defined in a multi-key setting, such that CoPRF evaluation keys are derived from a master secret.

Structs

CoPRFEvaluatorContext

The coPRF evaluator holds the coPRF master secret.

CoPRFReceiverContext

The coPRF receiver needs an unblinding private key in order to obtain the final coPRF output from the blinded evaluation result.

CoPRFRequesterContext

The coPRF requester requires the blinding public key of the intended receiver of the PRF output.

Functions

derive_key

E.1.5. Evaluation Key Derivation

Type Aliases

BlindingPrivateKey

As unblinding is performed by Elgamal decryption, the unblinding private key is an Elgamal decryption key.

BlindingPublicKey

As blinding is performed by Elgamal encryption, the blinding public key is an Elgamal encryption key.

CoPRFKey

A coPRF evaluation key is a scalar for the base group of the scheme, in our case P256.

CoPRFKeyID

A coPRF evaluation key is identified by a bytestring of arbitrary length.

CoPRFMasterSecret

The master secret for generating coPRF keys. It is fixed to a length 32 bytes since that is the number of bytes necessary as an input for HPKE-style key derivation when targeting scalars in P256. Per the HPKE RFC [RFC9180] it is crucial that a minimum of Nsk bytes of entropy is provided to the key derivation algorithm, where Nsk is the number of bytes to represent a valid private key, i.e. a P256 scalar in our case.