A digital certificate provides a convenient way of distributing trusted public encryption keys.

Example Usage

To illustrate we will look at a typical web browser and web server connection using SSL. (https).

This connection is used on the Internet to send email in Gmail etc and when doing online banking,shopping etc.

  1. Browser connects to server Using SSL (https)
  2. Server Responds with Server Certificate containing the public key of the web server.
  3. Browser verifies the certificate by checking the signature of the CA. To do this the CA certificate needs to be in the browser’s trusted store( See later)
  4. Browser uses this Public Key to agree a session key with the server. (session key is for symmetric encryption)
  5. Web Browser and server encrypt data over the connection using the session key.

References:

Excellent explanation on:

  • How SSL works
  • What are CA

https://youtu.be/iQsKdtjwtYI and related blog on SSL Certificates: http://www.steves-internet-guide.com/ssl-certificates-explained/