Pair-Fi: Integrity Code Protected Secure Device Pairing via SDR-Enabled Wi-Fi Chips on Smartphones

Abstract

Pairing of wireless devices, such as smartphones, suffers from a plethora of practical challenges if strong security guarantees via integrity codes are desired. Acoustic schemes are easy to deploy, but suffer from limited data rates and high sensitivity to environmental noise. Existing Wi-Fi-based methods, however, lack the necessary timing precision and signal flexibility to implement integrity codes on off-the-shelf devices. In this paper, we introduce Pair-Fi, a novel method that overcomes these limitations by leveraging integrity codes transmitted using software-defined radio (SDR)-like capabilities enabled through firmware modifications directly on smartphone-integrated Wi-Fi chips. Pair-Fi demonstrates both transmission and reception of raw IQ samples directly on commodity smartphone hardware, allowing for precise on-off keying modulation with timing resolution as low as 4 µs slots. By bypassing the constraints of conventional Wi-Fi frame timings, our approach significantly improves pairing speed, reliability, and resistance to interference. We validate Pair-Fi experimentally on recent smartphone models, such as the Google Pixel 7, showing robust performance in realistic environments. Our results indicate that SDR-enabled integrity code pairing via smartphone Wi-Fi chips provides a practical, secure, and efficient alternative to existing device pairing mechanisms, opening new avenues for secure and seamless device interactions in everyday scenarios.