Which of the following are not steps in setting up a TLS session?
A.
Client sends Hello to Server listing all of its supported cipher suites
B.
Client calculates and sends encrypted pre_master_secret
C.
Server sends-Hello to Client listing all of is supported cipher suites
D.
Server sends Change Cipher Spec to indicate a shift to encrypted mode
E.
Client and Server calculate keys from pre_master_secret
Explanation:
Transport Layer Security (TLS) IETF RFC 4507 / RFC4507 These goals are achieved by the handshake protocol, which can be summarized as follows: The client sends a client hello message to which the server must respond with a server hello message, or else a fatal error will occur and the connection will fail. The client hello and server hello are used to establish security enhancement capabilities between client and server. The client hello and server hello establish the following attributes: Protocol Version, Session ID, Cipher Suite, and Compression Method. Additionally, two random values are generated and exchanged:
ClientHello.random and ServerHello.random.
The client indicates that it supports this mechanism by including a SessionTicket TLS extension in the ClientHello message. The extension will be empty if the client does not already possess a ticket for the server. The extension is described in Section 3.2. If the server wants to use this mechanism, it stores its session state (such as ciphersuite and master secret) to a ticket that is encrypted and integrity-protected by a key known only to the server. The ticket is distributed to the client using the NewSessionTicket TLS handshake message described in Section 3.3. This message is sent during the TLS handshake before the ChangeCipherSpec message, after the server has successfully verified the client’s Finished message.
Figure 1: Message flow for full handshake issuing new session ticket The client caches this ticket along with the master secret and other parameters associated with the current session. When the client wishes to resume the session, it includes the ticket in the SessionTicket extension within the ClientHello message. The server then decrypts the received ticket, verifies the ticket’s validity, retrieves the session state from the contents of the ticket, and uses this state to resume the session. The interaction with the TLS Session ID is described in Section 3.4. If the server successfully verifies the client’s ticket, then it may renew the ticket by including a NewSessionTicket handshake message after the ServerHello.
pre_master_secret This random value is generated by the client and is used to generate the master secret
When RSA is used for server authentication and key exchange, a 48- byte pre_master_secret is generated by the client, encrypted under the server’s public key, and sent to the server. The server uses its private key to decrypt the pre_master_secret. Both parties then convert the pre_master_secret into the master_secret, as specified above. If the client has a certificate containing fixed Diffie-Hellman parameters, its certificate contains the information required to complete the key exchange. Note that in this case the client and server will generate the same Diffie-Hellman result (i.e., pre_master_secret) every time they communicate.
