Efficient and secure key extraction using channel state information

Generating keys and keeping them secret are critical in secure communications. Due to the “open air” nature, key distribution is more susceptible to attacks in wireless communications. An ingenious solution is to generate secret keys for two communicating parties separately without the need of key exchange or distribution, and regenerate them on needs. Recently, it is promising to extract keys by measuring the random variation in wireless channels, e.g., RSS. In this paper, we propose an efficient secret key extraction protocol with decorrelating compressive (SKEDC). It establishes common cryptographic keys for two communicating parties in wireless networks via real-time measurement on channel state information (CSI). It outperforms RSS-based key generation approaches in terms of multiple subcarriers measurement, perfect symmetry in channel for key coincidence, rapid decorrelation with distance, and high sensitivity towards environments changes. In the SKEDC design, we also propose effective mechanisms, such as the adaptive key stream generation, to fully exploit the excellent properties of CSI and eliminate the correlation among the subcarriers. We implement SKEDC on off-the-shelf 802.11n devices and evaluate its performance via extensive experiments. The results demonstrate that SKEDC achieves more than 3× throughput gain in the key generation from the state-of-the-art RSS-based approaches.