[MS-WCCE] document contains several links to Netscape Keygen specifications that point to external resource. However, external resource no longer contain keygen specs. Example: §3.2.1.4.2.1.4.1.4 New Certificate Request Using KEYGEN Request Format. Document contains a link to Microsoft forwarder (https://go.microsoft.com/fwlink/?LinkId=166240) and forwarder redirects to a page that doesn't contain any Keygen specs anymore.
I tried to find something more reliable and didn't find much. The closest is Mozilla Developer Network: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/keygen.