Is there a valid way to put up a paper on arXiv or GitHub and make it private just before a conference? I wrote a paper and it has been in limbo for more than a year because I need to re-write the code in C++ to get more proof of my algorithm before sending it to a conference.
To avoid being scooped, I considered putting it on arXiv, but was wary of exposing the algorithm to the public and I heard that it messes with the conference reviewer's double blind review.  

So if arXiv and HAL archives do not have the option to keep a paper private, would uploading the paper to GitHub in a private repository serve as proof if I ever need to prove that I came up with the idea first, if I've been scooped? This way, I would be able to give private access to the repository to whoever is investigating. I wonder if this would get counted as scooping if the person who scooped the idea never knew about my paper because it was in a hidden private repository.
would uploading the paper to GitHub in a private repository serve as proof if I ever need to prove that I came up with the idea first, if I've been scooped? 


You can prove you came up with the idea first, but you can still be scooped, since credit will be given to the first public work.