Certificate Transparency (CT)
acronymcryptographysecurity
The system requiring publicly issued certificates to be recorded in append-only public logs, with browsers refusing certificates that lack proof of logging - so that any issuance for any domain is observable by anyone.
It changed the security model rather than strengthening the old one: authorities can still misissue, but they cannot do it secretly, and detection moves from impossible to a matter of hours. Domain owners get a free, direct benefit - monitor the logs for your own names and you learn immediately when someone certifies them. The broader idea generalises well beyond certificates: when trust cannot be verified in advance, make the exercise of that trust public and auditable after the fact.
Also known as: ct logs, sct, merkle log, crt.sh