Implementation of Anonymous Credential System with Efficient Proofs for Monotone Formulas on Attributes Excluding Restriction

Abstract

An anonymous credential system allows a user to convince a service provider anonymously that he/she owns certified attributes. Previously, we proposed an anonymous credential system to prove user's attributes to satisfy a monotone formula, i.e., A logic relation with any combination of AND/OR relations. However, this system has a restriction that the user can prove the monotone formula when only one attribute is true for any OR relation. Recently, we proposed the improved system to overcome the restriction, by adopting Linear Homonorphic (LH) signature scheme to generate a certificate that contains the minimum attribute set as required in the verification. However, the improved system has never been implemented, and thus the practicality is not evaluated. In this paper, we implement the system using a fast pairing library, and measure the processing times and data sizes, when changing the number of user's attributes and the size of the proved relation.