u6.3 TLS Handshake_1

u6.3 TLS Handshake_1

1. Used for key establishment

2. To setup the secure channel between client and server before the application data is transmitted.

3. Agree parameters with which to set-up the secure channel

4. Each party has a notion of a current state that the connection is in and the current state determines the current level of protection.

   • During this current state the next state or 'pending state' is negotiated using the handshake protocol
     • The pending state defines the secure channel that is going to be used once the parameters are negotiated.
       • The initial state prior to the TLS session is called the 'null state'.
         • The negotiation sets up the pending state and what the keys will be
           • Once both sides are ready to move to the next state, the pending state becomes the current state.

5. The Negotiation specifies

   • bulk cipher with which to encrypt the session;
   • MAC algorithm with which to provide data integrity
   • key size
   • key material from which to produce the keys for authentication and encryption.

6. Handshake Steps

   • 1st - Exchange hello messages
     • Initiator sends a client hello which contains random numbers. The hello message includes a list of the suggested cipher suites to be used.
       • The responder replies with a server hello, this also contains random numbers & chosen cipher suite to be set up
         • 2nd - agree secret material for pre-master secret and authenticate parties
           • Both parties
             • Exchange the necessary cryptographic parameters to allow the client and server to agree on a pre-master secret.