Information Theoretic HotStuff

TL;DR

This paper introduces IT-HS, an information-theoretic Byzantine agreement protocol that is optimally resilient, does not rely on PKI, and achieves efficient communication and storage in partial synchrony.

Contribution

IT-HS is the first information-theoretic HotStuff-like protocol that is resilient to unbounded adversaries and does not depend on PKI or setup assumptions.

Findings

Achieves $O(n^2)$ message complexity per view.

Requires only $O(1)$ persistent storage per node.

Ensures fast decision after system becomes synchronous.

Abstract

This work presents Information Theoretic HotStuff (IT-HS), a new optimally resilient protocol for solving Byzantine Agreement in partial synchrony with information theoretic security guarantees. In particular, IT-HS does not depend on any PKI or common setup assumptions and is resilient to computationally unbounded adversaries. IT-HS is based on the Primary-Backup view-based paradigm. In IT-HS, in each view, and in each view change, each party sends only a constant number of words to every other party. This yields an $O(n^2)$ word and message complexity in each view. In addition, IT-HS requires just $O(1)$ persistent local storage and $O(n)$ transient local storage. Finally, like all Primary-Backup view-based protocols in partial synchrony, after the system becomes synchronous, all nonfaulty parties decide on a value in the first view a nonfaulty leader is chosen. Moreover, like PBFT and HotStuff, IT-HS is optimistically responsive: with a nonfaulty leader, parties decide as quickly as the network allows them to do so, without regard for the known upper bound on network delay. Our work improves in multiple dimensions upon the information theoretic version of PBFT presented by Miguel Castro, and can be seen as an information theoretic variant of the HotStuff paradigm.