PHY-Based Key Agreement Scheme using Audio Networking

The widespread use of wireless technologies goes hand in hand with the need for finding practical and less expensive solutions for securing communication. Establishing a shared secret key is considered to be the first step in any security system. In this regard, many solutions have been offered from classical cryptography (i.e. computational security) based solutions to physical layer (i.e. information-theoretic security) based ones. Recently, some of the physical characteristics of the wireless channel have been leveraged for the purpose of secret key establishment. Most of the proposed works in this domain consider exploiting the properties of the wireless radio channel. However, motivated by the high prevalence of smart-phones and their applications, and differently from previous works, in this paper we introduce an alternative solution for PHY-based key agreement over a limited communication range, more specifically, room range audio communication between smartphones. The use of audio channel allows implementation on off the shelf smartphones. We validate and analyse the proposed system through real world experiments. We find that our system produces significantly high key generation rate in comparison with the existing radio based solutions. In addition, the system is robust against eavesdropping and brute force attacks.