Cybersecurity glossary
What is SSL/TLS?
Learn what SSL/TLS is, how TLS handshakes authenticate servers and encrypt traffic, why SSL is obsolete, and modern TLS configuration best practices for HTTPS.
Definition
SSL/TLS refers to cryptographic protocols that secure network communications—historically Secure Sockets Layer (SSL) and its successor Transport Layer Security (TLS)—providing confidentiality, integrity, and server (and optionally client) authentication for protocols such as HTTPS.
Why SSL/TLS underpins the modern web
Without transport security, passwords, cookies, and APIs travel in cleartext. SSL/TLS provides the cryptographic tunnel that HTTPS, secure email submission, and many VPNs rely on.
SSL itself is retired; TLS 1.2 and 1.3 are the protocols that matter today—yet “SSL” remains common shorthand in certificates and marketing.
What TLS provides
Confidentiality
Symmetric encryption hides payloads from network observers after keys are established.
Integrity
MACs or AEAD ciphers detect modification of records in transit.
Authentication
X.509 certificates bind public keys to hostnames via trusted CAs.
Forward secrecy
Ephemeral key exchange limits damage if long-term keys are later stolen.
Simplified TLS handshake flow
ClientHello / ServerHello
Parties advertise supported versions and cipher suites.
Certificate and key exchange
Server presents a certificate; keys are agreed (ECDHE in modern suites).
Finished messages
Both sides confirm the handshake under the new keys.
Encrypted application data
HTTP or other protocols ride inside the protected record layer.
Configuration baseline
| Item | Guidance |
|---|---|
| Protocol versions | Enable TLS 1.2+; prefer TLS 1.3; disable SSL and TLS ≤1.1 |
| Cipher suites | AEAD suites only; disable RC4, 3DES, export, NULL |
| Certificates | Valid chain, correct names, automated renewal |
| HSTS | Tell browsers to stick to HTTPS after first visit |
| Testing | Continuous scans (SSL Labs, scanners) for regressions |
- Disable SSL 2.0/3.0 and TLS 1.0/1.1 on public services.
- Prefer TLS 1.3 where clients support it.
- Use strong ECDHE + AEAD cipher suites only.
- Automate certificate issuance and renewal (ACME).
- Enable HSTS with a sensible max-age once HTTPS is solid.
- Monitor for weak renegotiation, compression, and outdated libraries.
- Keep OpenSSL/BoringSSL/Schannel stacks patched.
- Treat “A+ on SSL Labs” as a baseline, not a one-time trophy.
The practical takeaway
SSL/TLS is the transport security layer of the internet. Use modern TLS, strong certificates, and continuous configuration hygiene—then still secure the application inside the tunnel.
Encryption in transit is mandatory; it is not a substitute for authorization, input validation, or safe session design.
Related security terms
Frequently asked questions
What is the difference between SSL and TLS?
SSL is the older protocol family and is obsolete. TLS is the modern standard. People still say “SSL certificate,” but servers should speak TLS.
What does TLS protect?
It encrypts data in transit, detects tampering, and authenticates the server (and optionally the client) using certificates.
Which TLS versions should I use?
Prefer TLS 1.2 and TLS 1.3. Disable SSL 2.0/3.0 and TLS 1.0/1.1 on modern services.
Is TLS enough for application security?
No. TLS protects the transport. Apps still need authz, input validation, and secure session handling.
What is a TLS handshake?
The initial negotiation where client and server agree on parameters, authenticate with certificates, and establish shared keys for the session.
Why do historical attacks like BEAST or POODLE matter?
They show why outdated SSL/TLS versions and weak ciphers must be disabled—modern configs remove those attack surfaces.
References
Explore authoritative guidance and frameworks related to ssl/tls.
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