As mentioned in LAN SSL Certificates, most, if not all, Unix based systems (which includes MacOS) come with an openssl program (named, surprisingly, openssl). Those programs are built (compiled) by people I trust, so I use them with few qualms.

This is not true for Microsoft Windows. And, since I do all of this kind of work on Unix, I'm not a good source. However, a little research found the following sources for prebuilt binaries (programs) for creating/manipulating SSL certficates under Windows. However, for maximum security, go to the openSSL Github repository and compile it yourself.

Ok, I found their copy of the openssl binary (program) at https://slproweb.com/products/Win32OpenSSL.html. Their web site has been in production since 2003, and a quick reputation search showed nothing nasty. Overall looks promising, and the web site definitely looks like a hacker (in the good sense, hacker is someone who enjoys working with computers). But I make no guarantees. Never used them, but they look like a for real service. Do your own research.

I found it through https://www.ssldragon.com/how-to/openssl/install-opnessl-windows/, of whom I know nothing. I also found it through TecAdmin, a web site with lots of ads but I've found decent info from them before.

The web site at https://medium.com/@bonguides25/how-to-download-and-install-openssl-in-windows-11-7551cfb52d44 suggests that you can get openssl using winget, Microsofts package search/download tool. Visit their web site for more information. winget search appearantly finds something called FireDaemon. Again, looks like a hacker (good kind) web site, so it is something I'd try, I guess.