Secure Multi-Party Comparing Protocol Based on Multi-Threshold Secret Sharing Scheme

The multi-party comparing problem with no information leaking is generalized from the millionaires´ problem, which is used to get whether these parties´ secret inputs are all equal and if not, the number of users whose inputs are the same to a indicated user Pn´s. Based on the semantic secure homomorphic encryption and the multi-threshold secret sharing scheme, a protocol of comparing multi-party information of equality is proposed. The correctness, security and efficiency are analyzed. The round complexity is two, the computation complexity is O(nk) modular exponentiations and the communication complexity is O(O²l) bits.