Abstract:

Abstract： The commitment scheme is one of the most fundamental components in cryptography， and is the basis of many cryptographic protocols， such as zero-knowledge proof and secure multi-party computing protocols. Universally composability （UC） is of great significance in designing secure protocols， if a protocol is proven secure in the UC framework， it still maintains security even if it is executed concurrently with arbitrary （even insecure） protocols. Several current efficient UC commitment schemes are all interactive protocols， and non-interactive UC commitments have high computational cost and communication complexity of the protocol. Aiming at solving this problem， an efficient UC-secure non-interactive commitment scheme in the common reference string model is proposed. The key design idea of universally composable commitments are to achieve extractability and equivocability at the same time. A CCA2-secure encryption scheme is used to achieve extractability in the commitment phase. A non-interactive zero-knowledge proof is used in the decommitment phase， and a dual-model commitment scheme is utilized to maintain protocol equivocability. The proposed protocol reduces the multi-round communication to one round in the open phase， achieving the non-interactivity. Compared with the existing non-interactive commitment scheme， the cost of computation and communication are greatly reduced， and the efficiency of the protocol is improved.

Key words: Key words： UC-security, commitment schemes, non-interactivity, common reference string