Shared Secret Key Generation by Exploiting Inaudible Acoustic Channels

Abstract

To build a secure wireless networking system, it is essential that the cryptographic key is known only to the two (or more) communicating parties. Existing key extraction schemes put the devices into physical proximity and utilize the common inherent randomness between the devices to agree on a secret key, but they often rely on specialized hardware (e.g., the specific wireless NIC model) and have low bit rates. In this article, we seek a key extraction approach that only leverages off-the-shelf mobile devices, while achieving significantly higher key generation efficiency. The core idea of our approach is to exploit the fast varying inaudible acoustic channel as the common random source for key generation and wireless parallel communication for exchanging reconciliation information to improve the key generation rate. We have carefully studied and validated the feasibility of our approach through both theoretical analysis and a variety of measurements. We implement our approach on different mobile devices and conduct extensive experiments in different real scenarios. The experiment results show that our approach achieves high efficiency and satisfactory robustness. Compared with state-of-the-art methods, our approach improves the key generation rate by 38.46% and reduces the bit mismatch ratio by 42.34%.

Secure and Efficient Data Transmission Scheme Based on Physical Mechanism

“…The third type of schemes is based on the acoustic channel. It exploits fast varying inaudible acoustic channel for generating enough randomness, and improves the key generation rate [13,14]. These schemes have strict requirements on the distance between the two sides of communication.…”

“…These schemes have strict requirements on the distance between the two sides of communication. For example, in [14], the best distance is between 50 and 70 cm, and its key generation rate is about 256 bps.…”

“…During the mismatched bit reconciliation stage, Alice and Bob will exchange some auxiliary data in the public communication channel, which will weaken the security key. In order to obtain superlattice symmetric key with information theory security, privacy amplification is necessary [14]. In the proposed scheme, Alice and Bob multiply sequence A p and B p with the same Toeplitz-like matrix to obtain the final symmetric key sequence A s and B s , where A s = B s .…”