SSL and TLS glossary: one term, one page

Terms defined here

• SSL and TLS

  are the old and current names for the same family of protocols, which is why the vocabulary mixes them freely and why the distinction matters less than people expect.

• TLS handshake

  is the negotiation before any data moves. Defined here in a sentence; taken apart step by step on the handshake page.

• Cipher suite

  is the named combination of algorithms two sides agree to use for a connection.

• SNI

  is the field that tells a server which name is being requested, so one address can present the right certificate among many. Configuring what gets sent to an origin belongs to another site in this network.

• HSTS

  is a declaration that a site should only ever be reached securely, remembered by the browser for a period the site states.

• mTLS

  is the arrangement where both sides present certificates rather than only the server.

• OCSP stapling

  is the server presenting recent proof that its certificate has not been revoked, instead of leaving the client to go and ask.

• Certificate transparency

  is the public logging of issued certificates, which is what makes an unexpected issuance discoverable rather than silent.

Definitions here, mechanics in the sections

An entry here answers what a term means, in a form you can read in half a minute. What happens during a connection is on TLS, what a certificate is and how it is obtained under certificates, how issuance is automated under ACME, and what a specific browser message means under errors, which sorts by the text you actually saw.

A term with a section of its own is better served by that section than by a paragraph here, which is why this list is shorter than the vocabulary of the subject.