Ecommerce sites use digital certificates to assure customers that theirs is a valid, secure site and not an impersonation (see the encyclopedia article on Phishing). These sites have public digital certificates that anybody can view. To see a site's digital certificate, click on the lock symbol that appears in the lower right-hand corner of the screen on secure web pages. A window will appear showing information about the site's digital certificate, including the issuer (e.g., if it is an internationally recognized organization such as Verisign ) and the time period the certificate is valid for.
Digital certificates can also be used to digitally sign documents. To sign a file, the sender attaches his encrypted digital certificate to it. Anyone who wants to read the file can then decrypt the digital signature and verify the certificate. This process assures the reader that the file was actually created by the person who digitally signed it, not an impersonator.