# The Network Impact of Hijacking a Quantum Repeater

## TL;DR

This paper analyzes the security impact of hijacking quantum repeaters in quantum networks, quantifies the workload and costs involved, and proposes a randomized testing method to prevent network disruption.

## Contribution

It introduces a quantitative framework for assessing the impact of quantum repeater hijacking and proposes a simple randomized testing approach to enhance security.

## Key findings

- Hijacking can cause significant work loss and rerouting penalties.
- Distributed quantum state tomography can detect hijacking costs.
- Randomized testing effectively prevents hijacking attacks.

## Abstract

In quantum networking, repeater hijacking menaces the security and utility of quantum applications. To deal with this problem, it is important to take a measure of the impact of quantum repeater hijacking. First, we quantify the workload of each quantum repeater with regards to each quantum communication. Based on this, we show the costs for repeater hijacking detection using distributed quantum state tomography and the amount of work loss and rerouting penalties caused by hijacking. This quantitive evaluation covers both purification-entanglement swapping and quantum error correction repeater networks. Naive implementation of the checks necessary for correct network operation can be subverted by a single hijacker to bring down an entire network. Fortunately, the simple fix of randomly assigned testing can prevent such an attack.