Compact Ring Signatures with Post-Quantum Security in Standard Model

Ring signatures allow a ring member to produce signatures on behalf of all ring users but remain anonymous. At PKC 2022, Chatterjee et al. defined post-quantum ring signatures with post-quantum anonymity and post-quantum blind-unforgeability. Assuming the hardness of the learning with errors problem, they proposed a generic construction that transforms any blind-unforgeable (BU) secure signature into a post-quantum ring signature in the standard model. However, the signature size grows linearly to the number of ring members. In this paper, we revisit the construction of Chatterjee et al. and present a compiler converting any BU secure signature into a compact (i.e., the signature size is logarithmically (or lower) dependent on the ring size) post-quantum ring signature in the standard model. Additionally, inspired by the work of Boneh et al. at CRYPTO 2013, we show how to transform any existentially unforgeable under a chosen message attack (EUF-CMA) secure signature into a BU secure signature. Hence, through our work, one can easily build a compact post-quantum ring signature in the standard model directly from any EUF-CMA secure signature.