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