The second computer system receives an encrypted message from the first computer system and processes {HEAD ~ the encrypted message} to generate {TAIL ~ a response message} 
The second computer system receives an encrypted message from the first computer system and processes { HEAD ~ the encrypted message } to generate { TAIL ~ a response message }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL