CompKey: Exploiting Computer’s Electromagnetic Radiation for Secret Key Generation

Secure communication between wireless devices has become an important issue for mobile devices. To achieve this, many efforts have been devoted to leveraging random ambient signals to generate a shared secret key between participating devices. However, the existing methods often suffer from limited authentication distance (e.g., less than 4cm for WiFi-based secret key generation). In this paper, we propose a novel secret key generation method, called CompKey, which allows wireless devices in the proximity of a computer to securely associate with each another by exploiting electromagnetic radiation (EMR) emitted from the computer. Unlike the existing approaches that often rely on ambient signals’ amplitudes, CompKey extracts the EMR’s frequency information, which fluctuates randomly with time, as a secret source. We design a difference-based encoding method, which preserves randomness of the frequency and avoids many consecutive zeros and ones in the generated key. We show via experiment evaluation that participating devices can reliably achieve around 10 bits/s bit generation rate and 100% key matching rate when they are located within 50cm away from the source computer. Moreover, the experiment results with the presence of attackers demonstrate that our method is robust against eavesdroppers and strong copy attackers who can imitate the key generation process.