Microsoft published a general explanation of digital signatures, certificates, and how they interact with MS Office documents.
Steven Levy’s book Crypto provides an entertaining history of public-key cryptography through 2001. The chapter “Patents and Keys” explores political and economic influences on federal digital signature standards in the 1990s.
A digital signature uses a public key to verify that a data item has not been altered.
Video notes: cys.me/vid/c12
Video #13 shows how to validate a public-key certificate vimeo.com/208878583
The previous video introduces public-key certificates for authenticating web sites vimeo.com/208069671
See the entire Cryptosmith series in its album vimeo.com/album/4229550