The remote service obtains {HEAD ~ a service authentication code} that has been generated, using {TAIL ~ a code generation} algorithm, based on a first secret key 
generated using
The remote service obtains { HEAD ~ a service authentication code } that has been generated , using { TAIL ~ a code generation } algorithm , based on a first secret key
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH