24-Hour Relativistic Bit Commitment

TL;DR

This paper demonstrates a practical 24-hour relativistic bit commitment protocol using high-speed optical communication and fast data processing, significantly extending previous secure durations and enabling real-world cryptographic applications.

Contribution

It presents the first long-duration (24-hour) relativistic bit commitment implementation, surpassing prior short-term protocols and showing feasibility for extended secure commitments.

Findings

Achieved 24-hour secure bit commitment in a real-world setting

Used high-speed optical communication and fast data processing

Potential to extend commitment duration to one year

Abstract

Bit commitment is a fundamental cryptographic primitive in which a party wishes to commit a secret bit to another party. Perfect security between mistrustful parties is unfortunately impossible to achieve through the asynchronous exchange of classical and quantum messages. Perfect security can nonetheless be achieved if each party splits into two agents exchanging classical information at times and locations satisfying strict relativistic constraints. A relativistic multi-round protocol to achieve this was previously proposed and used to implement a 2~millisecond commitment time. Much longer durations were initially thought to be insecure, but recent theoretical progress showed that this is not so. In this letter, we report on the implementation of a 24-hour bit commitment based on timed high-speed optical communication and fast data processing only, with all agents located within the city of Geneva. This duration is more than six orders of magnitude longer than before, and we argue that it could be extended to one year and allow much more flexibility on the locations of the agents. Our implementation offers a practical and viable solution for use in applications such as digital signatures, secure voting and honesty-preserving auctions.