Protocols for distributed key generation (DKG) in the discrete-logarithm setting have received a tremendous amount of attention in the past few years. Several synchronous DKG protocols have been proposed, but most such protocols either allow an attacker to bias the key, or are not robust in that they allow even a single malicious party to prevent successful completion of the protocol. We explore the round complexity of fully secure DKG in the honest-majority setting where it is feasible. On the negative side, we show the impossibility of one-round unbiased protocols regardless of any prior setup the parties have. On the positive side, we show various round-optimal protocols for fully secure DKG offering tradeoffs in terms of their efficiency, necessary setup, and required assumptions.
Jonathan Katz is a professor in the Department of Computer Science at the University of Maryland (UMD). His research interests lie broadly in the areas of cryptography, computer and network security, and theoretical computer science. He is a co-author of the widely used undergraduate textbook, “Introduction to Modern Cryptography,” now in its third edition (CRC Press, 2020). Katz has received numerous awards, including an Alexander von Humboldt Research Award, a UMD Distinguished Scholar-Teacher Award, and an ACM SIGSAC Outstanding Contribution Award. He is a fellow of the IACR and the ACM. He is currently on leave from the University of Maryland working at Dfns, a startup company using threshold cryptography to provide secure wallets-as-a-service.
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