Unable to prove I have the private key

I am a windows user and I will never, ever, upload my private key to a system even if it says it will encrypt it on my end first. My private key will never have anything to do with a web browser, nor will I type my password in anything other than a GnuPG password box. So The remaining two options are useless to me. I tried to install ubuntu in a vmware but the new interface is terrible and I could not find anything even a terminal.

To have someone prove that they own the private key all you need to do is generate a random long string, add it to the fingerprint of the person's public key they uploaded and ask them to digitally sign this text, then paste the result in the box provided, at which point the backend system checks and verifies that the person's public key is able to verify the text and that the text that was signed was the text requested to be signed by the system.

So, even though I was invited to test this, I am unable to even test any functionality until I can verify that I have the private key. I highly recommend this be done as soon as possible because not everyone is a linux god who breathes linux every day or is willing to upload their private key online.

No repository files, tests, or entry points are named. Start by reviewing the existing private-key verification options described in the issue, then determine where a signed random challenge would fit; done means the system verifies the uploaded public key against the user-provided signature without exposing the private key or password.

Written by the indexing model from the issue text.