Applying Consensus and Replication Securely with FLAQR

EasyChair Preprint no. 8249

Abstract

Availability is crucial to the security of distributed systems, but guaranteeing availability is hard, especially when participants in the system may act maliciously. Quorum replication protocols provide both integrity and availability: data and computation is replicated at multiple independent hosts, and a quorum of these hosts must agree on the output of all operations applied to the data. Unfortunately, these protocols have high overhead and can be difficult to calibrate for a specific application’s needs. Ideally, developers could use high-level abstractions for consensus and replication to write faulttolerant code by that is secure by construction.

This paper presents Flow-Limited Authorization for Quorum Replication (FLAQR), a core calculus for building distributed applications with heterogeneous quorum replication protocols while enforcing end-to-end information security. Our type system ensures that well-typed FLAQR programs cannot fail (experience an unrecoverable error) in ways that violate their typelevel specifications. We present noninterference theorems that characterize FLAQR’s confidentiality, integrity, and availability in the presence of consensus, replication, and failures, as well as a liveness theorem for the class of majority quorum protocols under a bounded number of faults.

Keyphrases: Availability, consensus, Replication

@Booklet{EasyChair:8249,
  author = {Priyanka Mondal and Maximilian Algehed and Owen Arden},
  title = {Applying Consensus and Replication Securely with FLAQR},
  howpublished = {EasyChair Preprint no. 8249},

  year = {EasyChair, 2022}}