Arbitrarily long relativistic bit commitment

TL;DR

This paper provides a new security analysis of a relativistic bit commitment protocol, showing that its complexity scales linearly with commitment time, enabling arbitrarily long secure commitments with simple classical communication.

Contribution

It offers a refined security analysis demonstrating linear complexity scaling, improving the feasibility of long-term relativistic bit commitments.

Findings

Complexity scales linearly with commitment time

Longer commitments are achievable with classical communication

Implementation is simplified due to classical computation requirements

Abstract

We consider the recent relativistic bit commitment protocol introduced by Lunghi et al. [Phys. Rev. Lett. 2015] and present a new security analysis against classical attacks. In particular, while the initial complexity of the protocol scaled double-exponentially with the commitment time, our analysis shows that the correct dependence is only linear. This has dramatic implications in terms of implementation: in particular, the commitment time can easily be made arbitrarily long, by only requiring both parties to communicate classically and perform efficient classical computation.