What is the purpose of ZKPoPK in the SPDZ paper? And will the following can detect the active adversaries in 2 party spdz excluding ZKPoPK step?
- Each party sends a commitment on his MAC key ∆_i before starting the offline phase.
- Parties select random a_i and b_i and broadcast the encryption on a_i, b_i, ∆_i
- These encryptions can be added up and multiplied using FHE to produce encryptions of (a · b, a · ∆, b. ∆, a · b · ∆)
- Using the distributed decryption to allow the parties to receive an additive secret sharing of each of those values
- Same procedure can be used to authenticate the inputs of each party
- Circuit Evaluation
- Reveal the output and the mac keys