%%%%%%

Abstract: Information-theoretic security is largely physical; The security of cryptographic protocols can be based, and has been based, on diverse physical assumptions. Amongst them, most notably, quantum mechanics. But also, the fatality of noise in communication channels, the difficulty of storing very large information strings, special relativity... What about thermodynamics? To address that question, I will present a theoretical model: a classical-information world where large randomized memories are accessible and reversible computation is effortless, but energy is severely limited. I will present in that world two information-theoretically secure protocols; they realize universal primitives for secure communication and secure multipartite computation (i.e., secret key establishment and 1–2 oblivious transfer). I will finish by debunking the security of those protocols in a world where information is not classical, but contextual — however, differently than according to quantum mechanics. The security in a quantum mechanical world of those two protocols is still unknown.