In response, the first computer system generates {HEAD ~ a message}, encrypts the generated message, and transmits the encrypted message to {TAIL ~ the second computer system} 
In response , the first computer system generates { HEAD ~ a message } , encrypts the generated message , and transmits the encrypted message to { TAIL ~ the second computer system }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL