Communication system and method

A terminal of a communication system comprising said terminal, a telecommunications network server capable of providing at least one network service to the terminal, and at least one application server capable of providing application services to the terminal via the telecommunications network and the telecommunications network server,

• the terminal comprising:
• a processor;
• and
• a non-transitory computer-readable medium comprising instructions stored thereon which when executed by the processor configure the terminal to perform acts comprising:
• storing a “network root key” shared with the network server and kept secret with regard to said application server;
• generating from this network root key, at least one “network session key”;
• signing and/or verifying messages exchanged between the terminal and the network server by using the network session key;
• storing at least one “application root key” shared with the application server, and kept secret with regard to the network server;
• obtaining at least one “application session key” from the application root key shared with the application server;
• and
• performing at least one of encrypting or decrypting messages exchanged between the terminal and the application server via the network by using the application session key generated by the second generating module.

A communication method within a communication system comprising a terminal, a telecommunications network server capable of providing at least one network service to the terminal, and at least one application server capable of providing application services to the terminal via the telecommunications network and the telecommunications network server, this communication method comprising:

• a first act of connecting the terminal to the network server comprising a generation by the terminal and by the network server of a “network session key” from a network root key shared between the terminal and the network server and kept secret with regard to the application server, this network session key to be used for signing and verifying integrity of messages exchanged on the network between the terminal and the network server;
• a second act of connecting the terminal to the application server, this second connecting act comprising a generation by the terminal and by the application server of an “application session key” from the application root key shared between the terminal and the application server and kept secret with regard to the network server, this application session key to be used for encrypting and decrypting messages exchanged between the terminal and this application server via the network;
• said at least one second connecting act being implemented after the completion of the first connecting act.