RadSec (RADIUS over TLS) replaces the traditional MD5-based Pre-Shared Key (PSK) with a secure TLS tunnel. While the UI might show a placeholder "radsec" PSK, the actual security relies on Mutual Authentication via certificates. For the TLS handshake to succeed, ClearPass must trust the Certificate Authority (CA) that signed the NAD's certificate, and vice versa. Therefore, verifying that the NAD's trust chain is uploaded to the ClearPass Trust List is the most critical step for a successful connection.