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