Fingerprinting Encrypted Voice Traffic on Smart Speakers with Deep Learning

TL;DR

This study demonstrates that deep learning can effectively fingerprint encrypted voice traffic from smart speakers, revealing user commands with high accuracy and proposing a defense to mitigate this privacy risk.

Contribution

The paper introduces a novel deep learning-based attack on encrypted voice traffic of smart speakers and proposes an effective traffic obfuscation defense.

Findings

Attack achieves 92.89% accuracy on Amazon Echo

Defense reduces attack accuracy to 32.18%

Effective fingerprinting even with only incoming traffic

Abstract

This paper investigates the privacy leakage of smart speakers under an encrypted traffic analysis attack, referred to as voice command fingerprinting. In this attack, an adversary can eavesdrop both outgoing and incoming encrypted voice traffic of a smart speaker, and infers which voice command a user says over encrypted traffic. We first built an automatic voice traffic collection tool and collected two large-scale datasets on two smart speakers, Amazon Echo and Google Home. Then, we implemented proof-of-concept attacks by leveraging deep learning. Our experimental results over the two datasets indicate disturbing privacy concerns. Specifically, compared to 1% accuracy with random guess, our attacks can correctly infer voice commands over encrypted traffic with 92.89\% accuracy on Amazon Echo. Despite variances that human voices may cause on outgoing traffic, our proof-of-concept attacks remain effective even only leveraging incoming traffic (i.e., the traffic from the server). This is because the AI-based voice services running on the server side response commands in the same voice and with a deterministic or predictable manner in text, which leaves distinguishable pattern over encrypted traffic. We also built a proof-of-concept defense to obfuscate encrypted traffic. Our results show that the defense can effectively mitigate attack accuracy on Amazon Echo to 32.18%.