While executing the security server program, the server: verifies client access rights via a first encryption means, generates, encrypts and transmits to the client a random port number and a session key, and detects {HEAD ~ establishment} of a second connection between the client and {TAIL ~ a random port} of the server 
While executing the security server program , the server : verifies client access rights via a first encryption means , generates , encrypts and transmits to the client a random port number and a session key , and detects { HEAD ~ establishment } of a second connection between the client and { TAIL ~ a random port } of the server
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