Pattern-Based Alignment of Audio Data for Ad Hoc Secure Device Pairing

When studying the use of ambient audio to generate a secure cryptographic shared key among mobile phones, we encounter a misalignment problem for recorded audio data. The diversity in software and hardware causes mobile phones to produce badly-aligned audio chunks. It decreases the identical fraction in audio samples recorded in nearby mobile phones and consequently the common information available to create a secure key. Unless the mobile devices are real-time capable, this problem can not be solved with standard distributed time synchronisation approaches. We propose a pattern-based approximative matching process to achieve synchronisation independently on each device. Our experimental results show that this method can help to improve the similarity of the audio fingerprints, which are the source to create the communication key.