This is the shared secret used to cryptographically sign and validate RADIUS packets exchanged with the server, so it must exactly match what's configured on the RADIUS server itself. A mismatch here is one of the most common causes of RADIUS authentication silently failing even though the server is reachable and otherwise correctly configured, and reading this object back always returns blank by design, so a config audit can't recover a forgotten key this way. For example, if the shared secret was changed on the RADIUS server during a routine rotation but not updated here, every login attempt would start failing even though the network path to the server remains fine.