Paper 2022/1432 Original: eprint.iacr.org/2022/1432 ↗

A Lattice-based Ring Signature Scheme Secure against Key Exposure

Abstract

A ring signature scheme allows a group member to generate a signature on behalf of the whole group, while the verifier can not tell who computed this signature. However, most predecessors do not guarantee security from the secret key leakage of signers. In 2002, Anderson proposed the forward security mechanism to reduce the effect of such leakage. In this paper, we construct the first lattice-based ring signature scheme with forward security. Our scheme combines the binary tree and lattice basis delegation technique to realize a key evolution mechanism, where secret keys are ephemeral and updated with generating nodes in the binary tree. Thus, the adversary cannot forge the past signature even if the users' present secret keys are revealed. Moreover, our scheme can offer unforgeability under standard models. Furthermore, our proposed scheme is expected to realize post-quantum security due to the underlying Short Integer Solution (SIS) problem in lattice-based cryptography.