In operation, {TAIL ~ the authentication engine} receives a request having associated therewith {HEAD ~ a protect string} 
In operation , { TAIL ~ the authentication engine } receives a request having associated therewith { HEAD ~ a protect string }
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD