Using ambient audio in secure mobile phone communication

We study the use of ambient audio as a seed to non-interactively and communication-free generate a secure cryptographic key among mobile distributed devices. We have implemented an ambient audio-based secure device pairing on android mobile phones. This paper discusses practical problems we encountered related to hardware, environment and time synchronisation, introduces approaches for feature generation and details results from our experimental case studies. In the case study, we consider the impact of inter-device distance on the quality of generated keys.