Earlier quoted context omitted.
You can completely describe a crucial innovation without which your product would not be original or compelling, without completely describing your product and giving an instruction manual to start from nothing and build a better competitor to your business. In that case your "whole" business process or product would not be protected, but it is possible that by identifying the one thing you do better than your potent…
I really doubt that in 20 years something would not be reversed engineered or trivial by then. Moreover, patents are usually functional specifications, not algorithmic. In the rare cases where the description is vital, like perhaps crypto or coding patents, the published software already allows reverse engineering. Isn't the actual intention of patents to publicize the invention after the 20 years has gone by?
This is a bit of a nitpicky thing, but patenting crypto isn't really a great way of protecting your secrets - hiding away the algorithm is basically security by obscurity. Crypto has historically been one of those things that's made stronger by more scrutiny.