SSL

SSL (Secure Sockets Layer) is a protocol that encrypts the connection between a user's browser and a server, protecting transmitted data from eavesdropping and tampering. Although the name SSL is still widely used, the protocol itself has been retired — modern encryption is handled by its successor, TLS. Even so, the terms "SSL certificate" and "SSL encryption" remain part of everyday language.

How SSL works

At the heart of the mechanism is an SSL/TLS certificate — a digital file tied to a domain and issued by a trusted certificate authority (CA). When a browser connects to a site over HTTPS, a handshake takes place: the server presents its certificate, the two sides agree on keys, and from that point all transmission is encrypted. The certificate serves two roles:

• encryption — data (passwords, card details, forms) is unreadable to third parties,
• authentication — it confirms you are connecting to the real owner of the domain, not an impersonating site.

Certificates differ by level of verification: from simple DV (proof of control over the domain), through OV, to extended EV. Wildcard and multi-domain certificates are also available.

SSL in practice

An SSL certificate is now standard for every website — from a blog to an online store or banking. Without one, browsers display a "connection not secure" warning that deters users and harms reputation. Many hosting services offer free Let's Encrypt certificates with automatic renewal, so enabling HTTPS comes down to a few clicks. Thanks to SNI, a single server can serve many certificates for different domains on one IP address.