I'm using a Dell Latitude E6530 and I want to enroll my own keys for Secure Boot. I'm having a problem where when I use OpenSSL generated certificates, and try to enroll them via Expert Key Management option in the BIOS, I get this error

"Please make sure that the new key is properly formatted with signature list and serialization headers"

I'm having the same problem as the person in this thread which has no replies:

https://www.dell.com/community/Laptops-General-Read-Only/Unable-to-enroll-my-self-signed-keys-using-quot-Replace-from/td-p/4164459

I've been following this guide UEFI Secure Boot for Linux guide

But it uses tools that are only available on Linux. Why doesn't this work? Is there a Windows guide for how to generate the keys in the correct format?

Thanks