Cryptology ePrint Archive: Report 2020/142

Network-Agnostic State Machine Replication

Erica Blum and Jonathan Katz and Julian Loss

Abstract: We study the problem of $\textit{state machine replication}$ (SMR) -- the underlying problem addressed by blockchain protocols -- in the presence of a malicious adversary who can corrupt some fraction of the parties running the protocol. Existing protocols for this task assume either a $\textit{synchronous network}$ (where all messages are delivered within some known time $\Delta$) or an $\textit{asynchronous network}$ (where messages can be delayed arbitrarily). Although protocols for the latter case give seemingly stronger guarantees, in fact they are incomparable since they (inherently) tolerate a lower fraction of corrupted parties.

We design an SMR protocol that is network-agnostic in the following sense: if it is run in a synchronous network, it tolerates $t_s$ corrupted parties; if the network happens to be asynchronous it is resilient to $t_a\leq t_s$ faults. Our protocol achieves optimal tradeoffs between $t_s$ and $t_a$.

Category / Keywords: applications / consensus, blockchain

Original Publication (in the same form):

Date: received 9 Feb 2020

Contact author: erblum at cs umd edu,jkatz2@gmail com,lossjulian@gmail com

Available format(s): PDF | BibTeX Citation

Version: 20200210:194118 (All versions of this report)

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