TLS (Transport Layer Security) is the cryptographic protocol that secures internet communications. SSL (Secure Sockets Layer) is its deprecated predecessor — SSL 2.0, 3.0, TLS 1.0, and TLS 1.1 are all insecure and should be disabled. TLS 1.2 and TLS 1.3 are the current secure versions.
The term “SSL certificate” persists colloquially — all modern “SSL certificates” are used with TLS.
TLS Handshake (Simplified)
Client → Server: Hello (supported cipher suites, random)
Server → Client: Hello + Certificate + (key exchange)
Both parties: Derive shared session key
Encrypted data beginsTLS 1.3 reduces this to 1 round trip; TLS 1.2 requires 2.
Certificate Role
An SSL/TLS certificate:
- Authenticates the server — proves it controls the domain
- Provides the public key for the key exchange
- Is signed by a Certificate Authority that browsers trust
Versions
| Version | Status |
|---|---|
| SSL 2.0, 3.0 | Broken — disable |
| TLS 1.0, 1.1 | Deprecated — disable |
| TLS 1.2 | Acceptable — still widely used |
| TLS 1.3 | Current standard — fastest and most secure |
HTTPS
HTTPS = HTTP + TLS. The padlock icon in browsers indicates an active TLS connection. It proves the connection is encrypted and the certificate is valid — but not that the site is legitimate or safe.