That's okay as well, the problem is, how do you do this correctly? You cannot store it in the cloud because that's a bad idea. Where else? If you give someone

That's okay as well, the problem is, how do you do this correctly? You cannot store it in the cloud because that's a bad idea. Where else? If you give someone a key to the device, how does the device itself enforce a time-limited key, especially if the crypto-based components are about to be replaced?