This OCTET STRING object holds the shared secret used to authenticate and encrypt communication with the configured RADIUS server; for security reasons, reading this field always returns an empty string. Admins set this to the same secret configured on the RADIUS server itself, since a mismatched secret will cause all authentication requests to that server to fail. For example, an admin configuring RADIUS authentication would write the pre-shared secret key here to match what's set on the RADIUS server, even though a subsequent read-back would show nothing.