I used their land records and certificates of births, baptisms and deaths to follow them into the 1690's in Jamaica.
There can be complications when using different browsers, which means they need to use multiple certificates.
Or you don't have to use digital certificates.
To circumvent the need for public approval for borrowing, both the county and the school district have used certificates of participation.
Security is achieved by using digital certificates and encryption.
One goal of the current project is to find ways to allow both those objectives to be accomplished without using certificates.
Rebel groups and terrorists use phony end-user certificates in order to disguise where the weapons will wind up.
But other email programs you don't have to use certificates.
At this point you're basically using certificates or tokens from a trusted authority, which hopefully will replace passwords in general soon.
Using certificates in this manner increases the amount of authentication performed when sending mail.