Linked or unlinked: A systematic review of linkable ring signature schemes

As a prominent cryptographic primitive underlying anonymous communication, privacy-preserving cryptocurrencies, and other blockchain-based applications, ring signatures have garnered much attention in both research and industry over a decade with diverse guarantees of which linkability is an integral constituent. The linkability property enables any verifier to ascertain the fact that two ring signatures were generated by the same signer under a specified condition at the same time preserving signer anonymity. In this paper, we present a systematic investigation into linkable ring signature (LRS) schemes by reviewing 31 articles from 2006 to the first quarter of the year 2022 thereby providing readers with a broad synthesis of state-of-the-art information on LRS, current approaches to their constructions, security model, security guarantees, instantiation and applications. Our findings reveal non-uniformity in link tag constructions, diversity in underlying computational hard problems, and signature sizes as well as application areas. We point out the ramifications of construction paradigms as well as future research prospects aimed at providing guidance and reference for future research along this promising and vital cryptographic primitive. • Publications on linkable ring signature schemes from 2006 to the first quarter of 2022. • State-of-the-art of linkable ring signatures from diverse perspectives. • Insights on construction and linkability paradigms, security guarantees, and underlying cryptosystems. • Elucidation on design implications, application scenarios, and future prospects.