Paper 2021/1279

Quantum Diffie-Hellman Key Exchange

Dirk Fischer

Abstract

In 2014, the author conceived of a quantal version of the classical cryptographic Diffie-Hellman key exchange protocol. However, the paper was declined to be published (by a not disclosed journal). No further publication attempts were made by the author. In the time afterwards, the aforementioned idea was conceived by others as well, resulting in a number of publications regarding this topic and even slight improvements. Thereby underlining the significance of the author's original idea, despite of being rejected by peer reviewed journals. The paper at hand therefore serves two purposes: First, it might serve others (especially young researchers) as an example to not feel discouraged by publication refusals, if they truly deem them as important novelties. Second, it provides an easy to understand introduction to grasp the concept of a quantum Diffie-Hellman key exchange. All of the following paragraphs, including the remainder of this abstract, are taken from the original 2014 publication attempt and are unchanged in comparison to the 2014 original: In this work, a quantal version of the classical cryptographic Diffie-Hellman key exchange protocol is introduced. It is called Quantum Diffie-Hellman key exchange. Unlike for the existing quantum key distribution protocols, actual quantum states, and not their measurement outcomes, are regarded as finally exchanged keys/information. By implementation of that quantal Diffie-Hellman version, both communication parties in the end are in possession of identically prepared, and secret quantum states. Thus the cryptographically important principle of forward secrecy is now available in a quantum physical framework. As a merit of the quantum setting, an improvement of the classical Diffie-Hellman protocol is also achieved, as neither of the two parties exactly know the final, exchanged states.