Universities are governed by masses of by-laws. Even if you read, understand and abide by all of them, you cannot confidently protect yourself against various accusations, e.g. plagiarism, academic misconduct, etc. You could even jeopardize your PhD.
The only reasonably "safe" approach is to buy your own PC, only work on your idea off campus and not publish, publicize or otherwise promote your work until after you graduate with your PhD. Keep a diary of your actual work, etc to be able to demonstrate that you did not utilize any of the universities resources for your project and that the essential IP is unrelated to your PhD research work.
I earned my PhD a few years ago and along the way I saw some of my colleagues get tripped up by the most specious academic rules. Cutting corners is not worth it.
The only reasonably "safe" approach is to buy your own PC, only work on your idea off campus and not publish, publicize or otherwise promote your work until after you graduate with your PhD. Keep a diary of your actual work, etc to be able to demonstrate that you did not utilize any of the universities resources for your project and that the essential IP is unrelated to your PhD research work.
I earned my PhD a few years ago and along the way I saw some of my colleagues get tripped up by the most specious academic rules. Cutting corners is not worth it.