Formal Verification of Quantum Protocols

TL;DR

This paper explores applying classical formal verification techniques to quantum protocols, specifically analyzing the BB84 quantum key distribution protocol using process calculus and model checking tools.

Contribution

It introduces a novel approach to verify quantum cryptographic protocols by adapting classical formal methods, demonstrated on the BB84 protocol.

Findings

Successful modeling of BB84 in process calculus

Initial verification results using CWB-NC

Potential for broader application to quantum information protocols

Abstract

We propose to analyse quantum protocols by applying formal verification techniques developed in classical computing for the analysis of communicating concurrent systems. One area of successful application of these techniques is that of classical security protocols, exemplified by Lowe's discovery and fix of a flaw in the well-known Needham-Schroeder authentication protocol. Secure quantum cryptographic protocols are also notoriously difficult to design. Quantum cryptography is therefore an interesting target for formal verification, and provides our first example; we expect the approach to be transferable to more general quantum information processing scenarios. The example we use is the quantum key distribution protocol proposed by Bennett and Brassard, commonly referred to as BB84. We present a model of the protocol in the process calculus CCS and the results of some initial analyses using the Concurrency Workbench of the New Century (CWB-NC).