RedHat provides an extensive explanation of certificates, what they are, and how they authenticate web sites, servers, clients, or people.
The Linux Documentation Project provides a “how to” about SSL certificates.
Durumeric, Kasten, Bailey, and Halderman presented 2013 results of a large-scale analysis of certificates actively used by SSL/TLS sites.
Describes how root certificate authorities delegate certificate signing to third party resellers, and how such certificates are validated.
Video notes: cys.me/vid/c15
The previous video describes how browsers handle multiple certificate authorities for validating public-key certificates vimeo.com/208879048
See the entire Cryptosmith series in its album vimeo.com/album/4229550