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