This report presents some technical details on the authentication process of a lightweight key exchange protocol, paying attention on how Man-in-the-Middle (MitM) attacks could undermine its security, e.g., under the scope of lawful interception and its risk to facilitate mass surveillance. We focus only on some technical aspects associated to the attack scenario. Perspectives for future work are also discussed. Other specific aspects of the work, mainly focusing on the security implications of malicious metasurfaces against B5G networks, are excluded from the scope of this report.