What is the reasoning behind the not rusty warning?

While I agree with the sentiment that it is technically stealing. No one should worry about charging their phone in public. Atleast in the region of the US I am located, it costs about 1-2 cents per year to charge your phone. So charging your phone for one sitting would be a miniscule amount of money. Just opening the door of the business and letting the conditioned air out would cost them more.

Obviously cars are an entirely different situation since one charge can be several if not tens of dollars.

I’m surprised I don’t see more people recommending KeePassDX! I agree and feel much more secure knowing exactly where my encrypted password vault is.

Also I recommend that people use Syncthing alongside KeePassDX so you can host your own cloudish environment to share the password vault between your devices. Keepass 2 is a great Windows/Linux application for interfacing with the .kbdx vault file format used by KeePassDX.

The problems which are calculated, such as finding prime factors of an integer, take non-polynomial (NP) time on a classical computer to solve. But NP problems, as opposed to NP-hard, can by definition be confirm in P (polynomial) time on a classical computer. Therefore, we can easily confirm that the answer is correct using classical computers.

On an aside, I used the example of prime factorization because it is one of the most well known problems that can be accelerated via quantum computing using Shor’s algorithm. Using Shor’s algorithm on a quantum computer, an integer can be factorized in P time. This is opposed to NP time on a classical computer.