Quantum Diffie-Hellman key exchange

TL;DR

This paper explores extending the classical Diffie-Hellman key exchange to quantum states, analyzing its security and practicality in the quantum setting with potential advantages and challenges.

Contribution

It introduces a quantum version of Diffie-Hellman using symmetric coherent states and analyzes its security against quantum attacks.

Findings

The quantum protocol can function as a quantum one-way function.

Security analysis shows resistance to certain quantum attacks.

Discussion of practical implementation challenges.

Abstract

The Diffie-Hellman key exchange plays a crucial role in conventional cryptography, as it allows two legitimate users to establish a common, usually ephemeral, secret key. Its security relies on the discrete-logarithm problem, which is considered to be a mathematical one-way function, while the final key is formed by random independent actions of the two users. In the present work we investigate the extension of Diffie-Hellman key exchange to the quantum setting, where the two legitimate users exchange independent random quantum states. The proposed protocol relies on the bijective mapping of integers onto a set of symmetric coherent states, and we investigate the regime of parameters for which the map behaves as a quantum one-way function. Its security is analyzed in the framework of minimum-error-discrimination and photon-number-splitting attacks, while its performance and the challenges in a possible realization are also discussed.