Efficient Fault-Tolerant Quantum Protocol for Differential Privacy in the Shuffle Model

TL;DR

This paper introduces a quantum protocol that securely and efficiently implements a random shuffle for differential privacy, avoiding classical trust issues and enabling fault-tolerant computation for any k-ary randomized response.

Contribution

A novel quantum protocol for differential privacy in the shuffle model that eliminates classical trust assumptions and supports fault-tolerant implementation for any k > 2.

Findings

Quantum shuffle protocol securely implements differential privacy.

Protocol avoids classical trust and computational requirements.

Supports efficient fault-tolerant implementation for any k > 2.

Abstract

We present a quantum protocol which securely and implicitly implements a random shuffle to realize differential privacy in the shuffle model. The shuffle model of differential privacy amplifies privacy achievable via local differential privacy by randomly permuting the tuple of outcomes from data contributors. In practice, one needs to address how this shuffle is implemented. Examples include implementing the shuffle via mix-networks, or shuffling via a trusted third-party. These implementation specific issues raise non-trivial computational and trust requirements in a classical system. We propose a quantum version of the protocol using entanglement of quantum states and show that the shuffle can be implemented without these extra requirements. Our protocol implements k-ary randomized response, for any value of k > 2, and furthermore, can be efficiently implemented using fault-tolerant computation.