TLS/SSL (Transport Layer Security / Secure Sockets Layer)

TLS (and its predecessor SSL) encrypt network traffic to protect confidentiality and integrity between clients and servers.

Protocol evolution

• SSL 1.0: Never released (security flaws).
• SSL 2.0/3.0: Deprecated (POODLE, BEAST attacks).
• TLS 1.0/1.1: Deprecated as of 2021.
• TLS 1.2: Current minimum standard.
• TLS 1.3: Latest version with improved performance and security.

How TLS works

• Handshake establishes secure connection and negotiates cipher suite.
• Public key cryptography authenticates server (and optionally client).
• Symmetric encryption protects data after handshake completes.
• Message authentication codes (MAC) verify data integrity.

Common uses

• HTTPS for secure web browsing.
• Email encryption (SMTPS, IMAPS).
• VPN tunnels and secure file transfers.
• API authentication and data exchange.

Implementation checklist

• Use TLS 1.2 or higher; disable SSL and TLS 1.0/1.1.
• Obtain certificates from trusted Certificate Authorities.
• Enable HTTP Strict Transport Security (HSTS) to force HTTPS.
• Configure strong cipher suites and disable weak algorithms.
• Monitor certificate expiration and implement automated renewal.