This value sets the shared secret authentication key, from 8 to 127 octets, used to secure communication with this RADIUS server; reading this object via SNMP always returns an empty string for security reasons. An admin sets this to the same shared secret configured on the RADIUS server itself, since a mismatch will cause all authentication requests to that server to fail. Because the key is write-only and never readable back, an admin must keep a record of what was configured elsewhere to audit or reconfigure it later.