Paper 2019/868
On the Round Complexity of Randomized Byzantine Agreement
Ran Cohen and Iftach Haitner and Nikolaos Makriyannis and Matan Orland and Alex Samorodnitsky
Abstract
We prove lower bounds on the round complexity of randomized Byzantine agreement (BA) protocols, bounding the halting probability of such protocols after one and two rounds. In particular, we prove that: (1) BA protocols resilient against $n/3$ [resp., $n/4$] corruptions terminate (under attack) at the end of the first round with probability at most $o(1)$ [resp., $1/2+ o(1)$]. (2) BA protocols resilient against $n/4$ corruptions terminate at the end of the second round with probability at most $1-\Theta(1)$. (3) For a large class of protocols (including all BA protocols used in practice) and under a plausible combinatorial conjecture, BA protocols resilient against $n/3$ [resp., $n/4$] corruptions terminate at the end of the second round with probability at most $o(1)$ [resp., $1/2 + o(1)$]. The above bounds hold even when the parties use a trusted setup phase, e.g., a public-key infrastructure (PKI). The third bound essentially matches the recent protocol of Micali (ITCS'17) that tolerates up to $n/3$ corruptions and terminates at the end of the third round with constant probability.
Metadata
- Available format(s)
- Category
- Cryptographic protocols
- Publication info
- Published elsewhere. Major revision. DISC 2019
- Keywords
- Byzantine agreementlower boundround complexity
- Contact author(s)
- rancohen @ ccs neu edu,iftachh @ cs tau ac il,n makriyannis @ gmail com,matanorland @ mail tau ac il,salex @ cs huji ac il
- History
- 2022-02-12: last of 3 revisions
- 2019-07-30: received
- See all versions
- Short URL
- https://ia.cr/2019/868
- License
-
CC BY