In this paper we generalize Lindell's solution using hash proof systems. The main advantage of our generic method is that it results in a simulation-based security proof without resorting to non-standard interactive assumptions.
Moving to concrete constructions, we show how to instantiate our framework using class groups of imaginary quadratic fields. Our implementations show that the practical impact of dropping such interactive assumptions is minimal. Indeed, while for 128-bit security our scheme is marginally slower than Lindell's, for 256-bit security it turns out to be better both in key generation and signing time. Moreover, in terms of communication cost, our implementation significantly reduces both the number of rounds and the transmitted bits without exception.
Category / Keywords: cryptographic protocols / threshold cryptography, two-party, ECDSA, hash proof systems, CL framework Original Publication (with minor differences): Advances in Cryptology - Proceedings of Crypto 2019 Date: received 15 May 2019, last revised 9 Jul 2020 Contact author: guilhem castagnos at math u-bordeaux1 fr,federico savasta@unict it,fabien laguillaumie@ens-lyon fr,catalano@dmi unict it,ida tucker@ens-lyon fr Available format(s): PDF | BibTeX Citation Version: 20200709:114437 (All versions of this report) Short URL: ia.cr/2019/503