A Multiparty Commutative Hashing Protocol based on the Discrete Logarithm Problem

Abstract

Let X and Y be two sets and suppose that a set of participants P = {P1, P2, . . . , Pn} would like to calculate the keyed hash value of some message m ∈ X known to a single participant in P called the data owner. Also, suppose that each participant Pi knows a secret value xi ∈ X. In this paper, we will propose a protocol that enables the participants in this setup to calculate the value y = H(m, x1, x2, . . . , xn) of a hash function H : X n+1 → Y such that: – The function H is a one-way function. – Participants in P\{Pi} cannot obtain xi. – Participants other than the data owner cannot obtain m. – The hash value y = H(m, x1, x2, . . . , xn) remains the same regardless the order of the secret xi values.