Securing Physical Layer Key Generation in Ambient Backscatter Devices Against Injection Attack

The necessity for ultra-low-power consumption devices that enable the Internet of Things (IoT) networks to be more energy efficient, leads to considering Ambient Backscatter Communication (AmBC). Such devices exploit ambient radio-frequency signals to communicate and harvest energy. Though, the physical layer key generation (PLKG) scheme that enables AmBC to generate a secret key for data encryption, is vulnerable to injection attacks. Under such a menace, an attacker injects predefined signals and contributes to the PLKG. Thereby, it possesses a part of the generated bits and uses brute force attack to compromise the entire key. Inspired by that, we carefully prove the vulnerability of the existing PLKG approach in AmBC to injection attack. Then, we propose the employment of a smart device that aims at detecting the attack and canceling the malicious signal. Furthermore, we propose a new strategy that enables legitimate devices to utilize the entire received ambient signal for PLKG while exploiting the malicious signal for energy harvesting. Hence, the attacker becomes the victim. Finally, we provide numerical simulations that accentuate the consequence of the menace and the effectiveness of our security method, even though only 80% of the injected signal is removed. Besides, we prove the efficacy of our energy harvesting strategy.