He could post a photo of a portion of the certificate.
Even a portion of it, will bring people forward to discredit it, causing doubt and decreasing the market value. But as I mentioned, its market value can be ascertained easily. It's the cost of a trip to Mombasa and a notary fee, if the document is genuine. (For that matter, it's probably just another $20 if it is not genuine. By next week, notarized 0bama bc's will be a cottage industry in Kenya.)