Post-Quantum Traceable Anonymous Credentials from Lattices

Traceable Anonymous Credentials (TACs) are an important extension of Anonymous Credentials (ACs). TAC systems protect user privacy during credential verifications while also allowing for the de-anonymization of credentials in cases of misbehavior. Although TACs have been studied with several constructions based on number-theoretic assumptions, the formal security definitions of credential tracing and efficient constructions with post-quantum security remain absent. This work addresses both gaps by presenting the first formalization of TACs and the first post-quantum construction based on module lattices. We design a new trapdoor for a lattice-based commitment, which allows partial recovery of commitment randomness. We integrate our trapdoor commitment into the state-of-the-art lattice-based AC system by Jeudy et al. (Crypto 2023) to derive our efficient TAC system.