Paper 2021/1368

Group Signatures and Accountable Ring Signatures from Isogeny-based Assumptions

Kai-Min Chung and Yao-Ching Hsieh and Mi-Ying Huang and Yu-Hsuan Huang and Tanja Lange and Bo-Yin Yang

Abstract

Group signatures are an important cryptographic primitive providing both anonymity and accountability to signatures. Accountable ring signatures combine features from both ring signatures and group signatures, and can be directly transformed to group signatures. While there exists extensive work on constructing group signatures from various post-quantum assumptions, there has not been any using isogeny-based assumptions. In this work, we propose the first construction of isogeny-based group signatures, which is a direct result of our isogeny-based accountable ring signature. This is also the first construction of accountable ring signatures based on post-quantum assumptions. Our schemes are based on the decisional CSIDH assumption (D-CSIDH) and are proven secure under the random oracle model (ROM).