At operation 2004 the reader retrieves a signing authority {HEAD ~ public key} , also known as {TAIL ~ a master} public key, from a signing authority 
At operation 2004 the reader retrieves a signing authority { HEAD ~ public key } , also known as { TAIL ~ a master } public key , from a signing authority
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH