Registering a moment of invention?

I invented something that I consider quite valuable. It is an idea for a mathematical method. It already works as intended, in a business process. I am not interested in patenting this shit, however, I want to make sure that I get the credit for this invention when (if ever) it becomes publicly known. So I would like some kind of real timestamping service. I would prefer something meatspace based, like a notary or US mail based or whatever. Any suggestions will be appreciated. igor