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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Bremermann's limit ： ウィキペディア英語版 Bremermann's limit Bremermann's Limit, named after Hans-Joachim Bremermann, is the maximum computational speed of a self-contained system in the material universe. It is derived from Einstein's mass-energy equivalency and the Heisenberg uncertainty principle, and is ''c''2/''h'' ≈ 1.36 × 1050 bits per second per kilogram.〔Bremermann, H.J. (1962) (''Optimization through evolution and recombination'' ) In: Self-Organizing systems 1962, edited M.C. Yovitts et al., Spartan Books, Washington, D.C. pp. 93–106.〕〔Bremermann, H.J. (1965) (Quantum noise and information ). 5th Berkeley Symposium on Mathematical Statistics and Probability; Univ. of California Press, Berkeley, California.〕 This value is important 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. For example, a computer with the mass of the entire Earth operating at the Bremermann's limit could perform approximately 1075 mathematical computations per second. If we assume that a cryptographic key can be tested with only one operation, then a typical 128 bit key could be cracked in under 10−36 seconds. However, a 256 bit key (which is already in use in some systems) would take about two minutes to crack. Using a 512 bit key would increase the cracking time to approaching 1072 years, without increasing the time for encryption by more than a constant factor (depending on the encryption algorithms used). The limit has been further analysed in later literature as the maximum rate at which a system with energy spread $\backslash Delta\; E$ can evolve into an orthogonal and hence distinguishable state to another, $\backslash Delta\; t\; =\; \backslash pi\; \backslash hbar\; /\; 2\; \backslash Delta\; E$. In particular, Margolus and Levitin has shown that a quantum system with average energy E takes at least time $\backslash Delta\; t\; =\; \backslash pi\; \backslash hbar\; /\; 2\; E$ to evolve into an orthogonal state. ==See also== *Bekenstein bound *Transcomputational problem *Limits to computation *Margolus–Levitin theorem *Landauer's principle 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Bremermann's limit」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.