What happens in a TLS handshake? | SSL ... - Cloudflare
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A TLS handshake enables clients and servers to establish a secure connection and create session keys. Learn more about how a TLS vs SSL handshake works.


What are the steps of a TLS handshake?
TLS handshakes are a series of datagrams, or messages, exchanged by a client and a server. A TLS handshake involves multiple steps, as the client and server exchange the information necessary for completing the handshake and making further conversation possible.

The exact steps within a TLS handshake will vary depending upon the kind of key exchange algorithm used and the cipher suites supported by both sides. The RSA key exchange algorithm is used most often. It goes as follows:

The 'client hello' message: The client initiates the handshake by sending a "hello" message to the server. The message will include which TLS version the client supports, the cipher suites supported, and a string of random bytes known as the "client random."
The 'server hello' message: In reply to the client hello message, the server sends a message containing the server's SSL certificate, the server's chosen cipher suite, and the "server random," another random string of bytes that's generated by the server.
Authentication: The client verifies the server's SSL certificate with the certificate authority that issued it. This confirms that the server is who it says it is, and that the client is interacting with the actual owner of the domain.
The premaster secret: The client sends one more random string of bytes, the "premaster secret." The premaster secret is encrypted with the public key and can only be decrypted with the private key by the server. (The client gets the public key from the server's SSL certificate.)
Private key used: The server decrypts the premaster secret.
Session keys created: Both client and server generate session keys from the client random, the server random, and the premaster secret. They should arrive at the same results.
Client is ready: The client sends a "finished" message that is encrypted with a session key.
Server is ready: The server sends a "finished" message encrypted with a session key.
Secure symmetric encryption achieved: The handshake is completed, and communication continues using the session keys.

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Note added at 20 perc (2022-03-05 12:42:45 GMT)
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Handshaking is the process that establishes communication between two networking devices. For example, when two computers first connect with each other through modems, the handshaking process determines which protocols, speeds, compression, and error-correction schemes will be used during the communication session.


Handshake Definition - TechTerms
https://techterms.com › definition › handshake
Oct 22, 2015 — A computer handshake may be completed between any two systems that communicate with each other on the same protocol. The two systems may be a ...