It is necessary for a TLS 1.3 message disguises itself as a TLS 1.2 one. The Version value at the second line is not a typo.
Handshake Protocol: Client Hello Version: TLS 1.2 (0x0303) Extension: supported_versions (len=11) Supported Versions length: 10 Supported Version: TLS 1.3 (0x0304) Supported Version: TLS 1.2 (0x0303) Supported Version: TLS 1.1 (0x0302) Supported Version: TLS 1.0 (0x0301) To better understand it, let’s look at an example of the extensions in TLS 1.3. To be compatible with the previous version, TLS 1.3 introduces the extensions. On March 21st, 2018, TLS 1.3 was finalized, bringing safer communication, better performance, and compatibility with TLS 1.2. TLS 1.2 came out in 2008 and is getting old. Now the handshake is done, and we are communicating in HTTPS. The browser sends its first encrypted request before receiving the server’s Finished message, saving the time to wait for the last message. With it, the server can verify whether the encryption is expected.įinally, the server sends a similar Change Cipher Spec message and the Finished message for encryption verification. In the Finished message, the browser includes an encrypted digest of all previous messages. Once the master secret is ready, the browser sends a Change Cipher Spec message letting the server know that all the future messages will be encrypted. Step 3 - Client key exchange and generate the master secret A signature, encrypted by the server’s private key, is attached to the param list for additional identity verification.įinally, the server sends the Server Hello message.Since ECDHE is selected, it puts key exchange algorithm params to the message.It adds a server certificate to prove its identity.An example of suggested cipher suites is TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384. TLS recommends using ECDHE (Ephemeral Elliptic-curve Diffie–Hellman) as the key exchange algorithm. It picks a preferred cipher suite from the list.It generates another 28-byte random number (Server Random).It saves the Client Random and puts it aside.It checks if the TLS version is a valid one.Step 2 - Server HelloĪfter receiving Client Hello, the server starts preparing Server Hello. The random number is essential, and we will use it later. a 28-byte random number (Client Random), and.The handshake starts with the Client Hello message from the browser.