SSL (Secure Sockets Layer) is a security protocol that requires a web server and browser to work together to establish an encrypted channel for the exchange of information. Seamless trust between a browser and server depends on the browser’s ability to trust the SSL provider.
When Servers and Browsers Connect:
- The browser requests identification.
- The server sends a copy of the SSL certificate.
- The browser checks whether it trusts the SSL certificate.
- When the browser trusts the SSL Certificate, it replies to the server.
- The server returns a digitally signed acknowledgment to start an SSL encrypted session.
- Encrypted data can now be shared between the browser and the server.
Trusting the SSL Certificate
A browser will check the source of the SSL Certificate issuer only when the SSL certificate is issued by a Certificate Authority that is known and trusted by the browser. The browser will display the content of the website secured by that SSL Certificate.
If the certificate is self-signed or issued by an unknown Certificate Authority, the browser may display an alert or security warning.
Root Certificate Ubiquity
Most browser vendors release their software with pre-installed root certificates from known Certificate Authorities. An SSL Certificate’s root ubiquity or level of browser recognition (also called browser compatibility) reflects the number of browsers that trust the Certificate Authority.
If an internet user is using an older or less well-known browser, it may be missing the root certificates. Hence, SSL Certificate providers do not claim that they have 100% browser compatibility.