Paper 2025/002 Original: eprint.iacr.org/2025/002 ↗

Voting with coercion resistance and everlasting privacy using linkable ring signatures

Abstract

We present a novel linkable ring signature scheme that possesses unconditional anonymity together with a voting protocol that utilizes it to achieve coercion resistance and everlasting privacy. In our system, all voters create private credentials and register their public counterparts. To vote, they create a ring (anonymity set) consisting of public credentials together with a proof of knowledge of their secret credential by using our novel signature. Its unconditional anonymity prevents an attacker, no matter how powerful, from deducing the identity of the voter, thus attaining everlasting privacy. Additionally, our protocol provides coercion resistance in the JCJ framework; when an adversary tries to coerce a voter, the attack can be evaded by creating a signature with a fake but indistinguishable credential. During a moment of privacy, the voter will cast their real vote. Our scheme also provides verifiability and ballot secrecy.