Universally-composable privacy amplification from causality constraints

TL;DR

This paper proves the security of secret key distribution schemes based on Bell inequality violations, relying only on causality constraints rather than quantum mechanics, enabling secure communication even with distrustful devices.

Contribution

It provides the first universally-composable security proof for Bell-based secret key schemes, independent of quantum mechanics assumptions.

Findings

Security proof based on causality constraints

Applicability to distrustful quantum devices

Enables secure communication without trusting quantum devices

Abstract

We consider schemes for secret key distribution which use as a resource correlations that violate Bell inequalities. We provide the first security proof for such schemes, according to the strongest notion of security, the so called universally-composable security. Our security proof does not rely on the validity of quantum mechanics, it solely relies on the impossibility of arbitrarily-fast signaling between separate physical systems. This allows for secret communication in situations where the participants distrust their quantum devices.