Concurrent/Resettable Zero-Knowledge With Concurrent Soundness in the Bare Public-Key Model and Its Applications

In this paper, we present both practical and general 4-round concurrent and resettable zeroknowledge arguments with concurrent soundness in the bare public-key (BPK) model. To our knowledge, our result is the first work that achieves concurrent soundness for ZK protocols in the BPK model and stands for the current state-of-the-art of concurrent zero-knowledge with setup assumptions. Since the BPK model is very simple and also very reasonable and is in fact a weak version of the frequently used public-key infrastructure (PKI) model, which underlies any public-key cryptosystem or digital signature scheme, we suggest that zero-knowledge protocols with simultaneous concurrent security in the BPK model may be of independent interests and can be used as a building block in other applications in the BPK model (e. g. secure two-party and multi-party computation with registered public-keys). For example, we show how to use our CZK-CS protocols to achieve cryptographic protocols with both concurrent player security and concurrent channel security (concurrent non-malleability) in the BPK model. We also give practical rZK and deniable authentication protocols in the preprocessing model.