Daniel Zentai, Mihail Plesa, and Robin Frot, xtendr, Hungary

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 : Xn+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.

Hash functions, Discrete logarithm problem, Anonymization