Using Hash-Based Signatures to Bootstrap Quantum Key Distribution

TL;DR

This paper explores replacing traditional MACs with hash-based signatures like Lamport's in Quantum Key Distribution, enhancing practical security while maintaining composable security guarantees.

Contribution

It demonstrates that hash-based signatures can be securely integrated into QKD protocols under standard assumptions, improving practical security and deployment.

Findings

Hash-based signatures can be securely used in QKD with existing security proofs.

The approach relies on standard one-way functions and computational assumptions.

Practical security of QKD is increased through this method.

Abstract

Quantum Key Distribution is a secret distribution technique that requires an authenticated channel. This channel is usually created on top of an un-authenticated communication medium using unconditionally secure Message Authentication Codes (MAC) and an initial common secret. We examine the consequences of replacing this MAC algorithm by a cryptographic hash-based signature algorithm, like the Lamport algorithm. We show that provided one-way functions exist, the Lamport algorithm or its variants can be instantiated in a secure way in the Universally Composable sense, and can therefore be plugged into any QKD protocol with a composable security proof in a secure manner. This association, while relying on short-term computational hardness assumptions, results in an increase of the practical security of QKD and eases its deployment.