There are only two known cryptographic algorithms that are "information-theoretically secure", essentially meaning they are proven impossible to break. Those are one-time-pad encryption, and Shamir's Secret Sharing.

The rest of them rely on more practical considerations. Asymmetric crypto is generally based on some mathematical problem that we don't know how to solve yet (and think we never will) while symmetric crypto is generally based on brute-force-style mixing up the bits so thoroughly they seem impossible to unmix.