I had that argument with another freeper. He claimed there are secret encryption algorithms. I stated that there are no secret encryption algorithms. Of course I have no way of knowing that. However the NSA along with NIST have developed several public encryption algorithms that were reviewed and critiqued by top worldwide encryption experts. Those algorithms are in fact used by the government and most US companies. It would go against all accepted practice to use a secret algorithm.
A company that invents and uses its own algorithm is not doing itself any favors. The secrecy must be in the key and the key alone in order to assure that the a cyber loss is not a catastrophe. If you lose a key in a cyber attack you have lost one key and life goes on. If you lose an algorithm which, being code, is harder to protect than a key which is data, that is a catastrophe.
Thus I would end any speculation about secret encryption algorithms. I speak strictly as an applied crypto expert with two decades of experience, not as an insider or anything like that.
While I personally would not pretend to know anything about it, I would think logic would dictate that if one had anything you wanted to secure behind encryption if you had the ability you would want to produce your own. Anything “off the shelf” would mean you could never be certain that what you were trying to secure, actually was secure.
As for me, personally, the answer is simple, do not have behavior or discussions that require such security. The old expression, “The only way two people can keep a secret is if one of them is dead.” comes to mind.