Cryptographic Fragility of Standard Quantum Repeater Protocols

TL;DR

This paper reveals vulnerabilities in standard quantum repeater protocols under adversarial conditions and proposes a cryptographic verification method to enhance security and stability.

Contribution

It identifies security flaws in existing quantum repeater protocols and introduces a cryptographic network stack with trapdoor verification to mitigate these issues.

Findings

Standard protocols can be manipulated in adversarial environments.

Diagnostic metrics may falsely indicate successful entanglement purification.

The proposed trapdoor verification enhances security without channel characterization.

Abstract

The security of the proposed quantum Internet relies on repeater protocols designed under the assumption of stochastic, characterizable noise. We demonstrate that in adversarial environments this assumption induces performance vulnerabilities for computationally bounded repeater nodes. We show that the standard BBPSSW distillation protocol recursively purifies error syndromes rather than entanglement. This leads to a state of low fidelity despite diagnostic metrics indicating perfect convergence. Moreover, we show that the verifier cannot check the adversarial influence via the maximum likelihood estimation algorithm since it is blind to computationally bounded observers. To address these vulnerabilities, we propose a Cryptographic Network Stack centered on a trapdoor verification protocol. The protocol exploits private randomness to restore operational stability without requiring channel characterization.