# Lightweight Physical Layer Aided Key Agreement and Authentication for the Internet of Things +
Footnote †: This paper is an extended version of our paper published in [PERSON]; [PERSON]; [PERSON] Physical Layer Aided Access for the Internet of Things. In Proceedings of the 14 th International Conference on Signal Processing and Communication Systems (ICSPCS'2020), Adelaide, Australia, 14-16 December 2020.  
[PERSON]  
1 School of Electrical Engineering and Computer Science, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea; [EMAIL_ADDRESS]  
[PERSON]  
2 Security Research and Development Team, Korea Atomic Energy Research Institute (KAERI), Daejeon 30407, Korea; ygjlkaerir.kr  
[PERSON]  
3 School of Information Technology, Deakin University, Geelong, VIC 3220, Australia; [EMAIL_ADDRESS]  
[PERSON]  
1 School of Electrical Engineering and Computer Science, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea; [EMAIL_ADDRESS]  
Footnote 1: [[https://www.mdpi.com/journal/electronics](https://www.mdpi.com/journal/electronics)]([https://www.mdpi.com/journal/electronics](https://www.mdpi.com/journal/electronics))  
Footnote 2: [[https://www.mdpi.com/journals/pdf/14](https://www.mdpi.com/journals/pdf/14)]([https://www.mdpi.com/journals/pdf/14](https://www.mdpi.com/journals/pdf/14))  
fast authentication [6; 7]. In particular, a physical layer challenge-response authentication mechanism (PHY-CRAM) [8; 9; 10] exploits characteristics of the physical channel to conceal the authentication key, preventing eavesdroppers from impersonating based attacks. However, PLA is inherently difficult to guarantee authentication performance in poor communication environments. As in [11; 12; 13; 14], cross-layer authentication schemes integrate PLA to cryptography-based authentication in order to compensate PLA, but simply cascading both layer schemes might be inefficient to apply in practical application due to the limited resources of the networks.  
In this paper, we consider a lightweight physical layer aided authentication and key agreement (PL-AKA) protocol for MIoT environments, providing a favorable balance between the signal overhead and reliability by selectively applying conventional cryptography-based authentication along with PLA and preliminary PLA decisions. To demonstrate the effectiveness of the proposed protocol, an experimental analysis is performed with a universal software radio peripheral (USRP). The main contributions of this paper are summarized as follows:  
* For sophisticated cross-layer authentication, we propose a novel integration strategy based on the test statistic result of the PHY-CRAM. By using this integration strategy, a proposed protocol can reduce the signaling overhead, while providing a competitive authentication performance. This is the main difference with existing cross-layer authentication protocols based on simple concatenation and encapsulation operations [11; 12; 13; 14].
* For the performance analysis, we analyze the authentication error probability and signaling overhead of the proposed protocol.
* For the validation of PLA in the proposed protocol, an RF experiment is conducted with USRP transceivers.  
Regarding notation, upper-case and lower-case boldface letters are used for matrices and vectors, respectively. \(\mathcal{CN}(\mu,\sigma^{2})\) represents the distribution of the circularly symmetric complex Gaussian (CSCG) random variable with mean \(\mu\) and variance \(\sigma^{2}\).