This OCTET STRING, up to 256 bytes, is the authentication key for this virtual interface; with simplePassword authentication the device left-adjusts and zero-fills it to 8 octets, and reading this object always returns a zero-length string for security. Because reads never reveal the actual key, an admin can only confirm the key is set by successfully establishing the virtual link's adjacency, not by reading this object back. An admin rotating this virtual link's authentication key must coordinate the new value out of band with the administrator of the neighboring router.