Sharing The Secret: Distributed Privacy-Preserving Monitoring

TL;DR

This paper proposes a distributed privacy-preserving monitoring architecture that uses secret-sharing to enable scalable, real-time, continuous monitoring with strong privacy guarantees, outperforming existing cryptographic methods.

Contribution

It introduces a novel distributed protocol for continuous monitoring using secret-sharing, improving scalability and efficiency over traditional cryptographic approaches.

Findings

Significantly reduced overhead compared to cryptographic methods

Supports continuous, stateful monitoring with privacy guarantees

Demonstrated scalability in experimental evaluations

Abstract

In traditional runtime verification, a system is typically observed by a monolithic monitor. Enforcing privacy in such settings is computationally expensive, as it necessitates heavy cryptographic primitives. Therefore, privacy-preserving monitoring remains impractical for real-time applications. In this work, we address this scalability challenge by distributing the monitor across multiple parties -- at least one of which is honest. This architecture enables the use of efficient secret-sharing schemes instead of computationally intensive cryptography, dramatically reducing over-head while maintaining strong privacy guarantees. While existing secret-sharing approaches are typically limited to one-shot executions which do not maintain an internal state, we introduce a protocol tailored for continuous monitoring that supports repeated evaluations over an evolving internal state (kept secret from the system and the monitoring entities). We implement our approach using the MP-SPDZ framework. Our experiments demonstrate that, under these architectural assumptions, our protocol is significantly more scalable than existing alternatives.