A Novel Attack Strategy on Entanglement Swapping QKD Protocols

TL;DR

This paper reveals a vulnerability in Li et al.'s entanglement swapping-based quantum key distribution protocol, introduces an attack that compromises its security, and proposes a modified, secure version.

Contribution

It introduces a novel attack strategy exploiting entanglement swapping and demonstrates a modified protocol that resists this attack.

Findings

The original protocol is insecure against the new attack.

The attack allows full key information extraction without detection.

The modified protocol is secure against the proposed attack.

Abstract

Li et al. presented a protocol [Int. Journal of Quantum Information, Vol. 4, No. 6 (2006) 899-906] for quantum key distribution based on entanglement swapping. In this protocol they use random and certain bits to construct a classical key and they claim that this key is secure. In our article we show that the protocol by Li et al. is insecure presenting a new type of attack strategy which gives an adversary full information about the key without being detected. This strategy is based on entanglement swapping, too, and manages to preserve the correlation between the measurement results of the legitimate parties. Further we present a modified version of the protocol and show that it is secure against this new attack strategy.