Bremermann's limit, named after Hans-Joachim Bremermann, is a theoretical limit on the maximum rate of computation that can be achieved in a self-contained system in the material universe.
It is derived from Einstein's mass–energy equivalency and the Heisenberg uncertainty principle, and is c2/h ≈ 1.3563925 × 1050 bits per second per kilogram.
[1][2] This value establishes an asymptotic bound on adversarial resources when designing cryptographic algorithms, as it can be used to determine the minimum size of encryption keys or hash values required to create an algorithm that could never be cracked by a brute-force search.
The limit has been further analysed in later literature as the maximum rate at which a system with energy spread
[3][4] In particular, Margolus and Levitin have shown that a quantum system with average energy E takes at least time