SSL/TLS

See that little padlock icon in your browser's address bar? That means SSL (or technically TLS, its newer version) is protecting your connection. Without it, everything you send to a website — passwords, credit card numbers, messages — travels in plain text that anyone snooping on the network could read.

Think of it like sending a postcard versus sending a letter in a sealed envelope. Without SSL, your data is the postcard — anyone handling it can read it. With SSL, it's the sealed envelope — only the intended recipient can open it. When you see "https" (the 's' stands for secure) instead of "http," that's SSL at work.

SSL is so important that modern browsers now warn you with scary messages if you visit a site WITHOUT it. Google even ranks HTTPS sites higher in search results. It went from "nice to have" to "absolutely required" in about a decade. The good news? It's free now thanks to services like Let's Encrypt and Cloudflare.

Because SSL is your first line of defense for online privacy. Before entering any sensitive information on a website, check for that padlock. No padlock? Don't enter your password or credit card number. It's also important if you build a website — without SSL, browsers will scare away your visitors with "Not Secure" warnings.

TLS (Transport Layer Security, successor to SSL) establishes encrypted communication channels using a handshake protocol: client hello, server certificate verification, key exchange (ECDHE), and session key derivation. TLS 1.3 reduced the handshake to one round-trip. Certificates are issued by Certificate Authorities (CAs) and verified via chain of trust. HSTS (HTTP Strict Transport Security) forces HTTPS. OCSP stapling, certificate transparency logs, and CAA DNS records enhance security. Free automated CAs like Let's Encrypt and Cloudflare's Universal SSL have made HTTPS ubiquitous.