What is an SSL certificate – Definition and Explanation

An SSL certificate is a digital certificate that authenticates a website’s identity and enables an encrypted connection. SSL stands for Secure Sockets Layer, a security protocol that creates an encrypted link between a web server and a web browser.

Companies and organizations need to add SSL certificates to their websites to secure online transactions and keep customer information private and secure.

In short: SSL keeps internet connections secure and prevents criminals from reading or modifying information transferred between two systems. When you see a padlock icon next to the URL in the address bar, that means SSL protects the website you are visiting.

Since its inception about 25 years ago, there have been several versions of SSL protocol, all of which at some point ran into security troubles. A revamped and renamed version followed — TLS (Transport Layer Security), which is still in use today. However, the initials SSL stuck, so the new version of the protocol is still usually called by the old name.
SSL works by ensuring that any data transferred between users and websites, or between two systems, remains impossible to read. It uses encryption algorithms to scramble data in transit, which prevents hackers from reading it as it is sent over the connection. This data includes potentially sensitive information such as names, addresses, credit card numbers, or other financial details.

The process works like this:

  1. A browser or server attempts to connect to a website (i.e., a web server) secured with SSL.
  2. The browser or server requests that the web server identifies itself.
  3. The web server sends the browser or server a copy of its SSL certificate in response.
  4. The browser or server checks to see whether it trusts the SSL certificate. If it does, it signals this to the webserver.
  5. The web server then returns a digitally signed acknowledgment to start an SSL encrypted session.
  6. Encrypted data is shared between the browser or server and the webserver.