Security of two-way quantum cryptography against asymmetric Gaussian attacks

TL;DR

This paper investigates the security of two-way continuous variable quantum cryptography against asymmetric Gaussian attacks, demonstrating that security benefits persist even with correlated eavesdropper interactions.

Contribution

It extends previous security analyses to asymmetric, classically correlated Gaussian attacks, showing that two-way protocols remain secure under these more general conditions.

Findings

Security enhancement persists with asymmetric Gaussian attacks

Two-way protocols are secure in direct reconciliation mode

Security holds even with classically correlated eavesdropper interactions

Abstract

Recently, we have shown the advantages of two-way quantum communications in continuous variable quantum cryptography. Thanks to this new approach, two honest users can achieve a non-trivial security enhancement as long as the Gaussian interactions of an eavesdropper are independent and identical. In this work, we consider asymmetric strategies where the Gaussian interactions can be different and classically correlated. For several attacks of this kind, we prove that the enhancement of security still holds when the two-way protocols are used in direct reconciliation.