Any chance of allowing me to upload my own keys and doing the signing in the browser? I am sure this is a niche use case but I know how to generate the certificate for this but have been too lazy to make a thing like this for (checks to-do list) something like six years and I'd much rather just use your thing lol

that's a good idea. i'll release a BYOK version but don't plan to host it myself. will include a quick run script to run it locally.

Haha, I just made a comment above that I've been sitting on a half done project to do this for around 8 years now.