What is TLS?
In one sentence: Transport Layer Security: the technology behind the padlock that encrypts web traffic.
A little more
TLS (Transport Layer Security) is what puts the S in HTTPS. When you connect, your browser and the server do a quick handshake: the server shows its certificate, and the two agree on fresh secret keys that nobody watching can work out.
Everything after that, including passwords and card numbers, is encrypted and checked for tampering. The handshake adds one quick round trip before the page starts loading.
It's a bit like… Two people agreeing a secret code in a crowded room in a way that eavesdroppers can't follow, then whispering in it.
See it in action
- 1What happens when you open a web page?Follow one click from your keyboard to a server and back: DNS, the padlock handshake, HTTP, tunnels and painting the page.6 min · interactive
- 4Secret codes: encryption and hashingFrom Caesar's cipher to the AES-256 lock behind every padlock: encrypt and decrypt in your browser, crack a code by brute force, and watch one letter change a SHA-256 fingerprint completely..7 min · interactive