What Is a TLS Handshake?

December 11, 2023

The TLS handshake is an authentication protocol that occurs at the beginning of a communication session between a client and a server. Here's a short overview of what happens during a TLS handshake:

  • The client initiates communication through a "ClientHello" message, specifying supported cryptographic algorithms.
  • The server responds with a "ServerHello" message, selecting compatible algorithms and confirming the connection.
  • Both parties exchange key info for a secure connection.
  • The server provides its digital certificate to the client to prove its identity.
  • The client verifies the certificate's authenticity and provides its own certificate for mutual authentication.
  • Both parties contribute to generating a pre-master secret crucial for encryption.
  • The handshake concludes with the exchange of "Finished" messages, indicating the completion of a handshake.
  • From this point, the client and server use the agreed-upon cryptographic algorithms to encrypt and decrypt exchanged data.

TLS handshakes establish the parameters of encrypted communication, ensuring the confidentiality and integrity of exchanged data. These handshakes are a foundational part of how HTTPS works.

Anastazija is an experienced content writer with knowledge and passion for cloud computing, information technology, and online security. At phoenixNAP, she focuses on answering burning questions about ensuring data robustness and security for all participants in the digital landscape.