Effect of Antenna Radiation Pattern Variation on the Secrecy Key Generation in LoS Indoor Environment Under On-The-Shoulder Attack

The upcoming Sixth-Generation (6G) communication systems bring several challenges to systems security. The Secrecy Key Generation (SKG) is a Physical Layer Security (PLS) technique in which two trusted nodes negotiate a session key, taking advantage of the physical layer phenomena, i.e., radio propagation and/or hardware characteristics, as a source of entropy. In this contribution, we investigate the impact of the variation of the antenna radiation pattern on the SKG performance. We considered two legitimate nodes that apply the SKG to negotiate their session key, whereas a malicious node tries to eavesdrop on the communication to obtain the key by performing the on-the-shoulder attack. The results highlight how the number of antenna dipoles, the Half Power Beamwidth (HPBW) of the main lobe, and the presence of secondary lobes or minima of radiation influence the key mismatch between the legitimate nodes as well as the eavesdropper attack surface.