This is an unencrypted authentication string which is carried in all HSRP messages. An authentication string mismatch prevents a router interface from learning the designated IP address or HSRP timer values from other HSRP-enabled routers with the same group number. The function of this object is not to supply any sort of security-like authentication but rather to confirm that what's happening is what's intended. In other words, this is meant for sanity checking only.