256-bit computing: Difference between revisions

Revision as of 07:41, 3 September 2024

Latest revision as of 19:19, 3 April 2025

(2 intermediate revisions by 2 users not shown)

Line 7:

A 256-bit quantity can store 2²⁵⁶ different values. The range of [[integer]] values that can be stored in 256 bits depends on the [[Integer (computer science)#Value and representation|integer representation]] used.

The range of a signed 256-bit integer is from -57,{{zwsp}}|−57,|896,{{zwsp}}|044,{{zwsp}}|618,{{zwsp}}|658,{{zwsp}}|097,{{zwsp}}|711,{{zwsp}}|785,{{zwsp}}|492,{{zwsp}}|504,{{zwsp}}|343,{{zwsp}}|953,{{zwsp}}|926,{{zwsp}}|634,{{zwsp}}|992,{{zwsp}}|332,{{zwsp}}|820,{{zwsp}}|282,{{zwsp}}|019,{{zwsp}}|728,{{zwsp}}|792,{{zwsp}}|003,{{zwsp}}|956,{{zwsp}}|564,{{zwsp}}|819,{{zwsp|968}}968 to 57,{{zwsp}}|57,|896,{{zwsp}}|044,{{zwsp}}|618,{{zwsp}}|658,{{zwsp}}|097,{{zwsp}}|711,{{zwsp}}|785,{{zwsp}}|492,{{zwsp}}|504,{{zwsp}}|343,{{zwsp}}|953,{{zwsp}}|926,{{zwsp}}|634,{{zwsp}}|992,{{zwsp}}|332,{{zwsp}}|820,{{zwsp}}|282,{{zwsp}}|019,{{zwsp}}|728,{{zwsp}}|792,{{zwsp}}|003,{{zwsp}}|956,{{zwsp}}|564,{{zwsp}}|819,{{zwsp967}}967.

256-bit processors could be used for addressing directly up to 2²⁵⁶ bytes. Already 2¹²⁸ (for [[128-bit computing|128-bit]] addressing) would greatly exceed the total data stored on Earth as of 2018, which has been estimated to be around 33.3 [[zettabyte|ZB]]s (over 2⁷⁴ bytes).<ref>{{cite book |last1=Reinsel |first1=David |last2=Gantz |first2=John |last3=Rydning |first3=John |title=The Digitization of the World |date=November 2018 |publisher=IDC |page=6 |url=https://www.seagate.com/files/www-content/our-story/trends/files/idc-seagate-dataage-whitepaper.pdf |access-date=27 October 2022}}</ref>

Line 29:

* 256 bits is a common [[key size]] for [[symmetric cipher]]s in [[cryptography]], such as [[Advanced Encryption Standard]] (AES).

* Increasing the word size can accelerate [[arbitrary-precision arithmetic|multiple precision]] mathematical libraries. Applications include [[cryptography]].

* Researchers at the [[University of Cambridge]] use a 256-bit capability pointer, which includes capability and addressing information, on early implementations of their [[Capability Hardware Enhanced RISC Instructions|CHERI]] capability system.<ref>{{cite web|url=http://www.csl.sri.com/users/neumann/2012resolve-cheri.pdf|title=CHERI: a research platform deconflating hardware virtualization and protection|last1=Watson|first1=Robert N. M.|author-link=Robert Watson (computer scientist)|last2=Neumann|first2=Peter G.|author2-link=Peter G. Neumann|date=3 March 2012|work=Unpublished workshop paper for RESoLVE’12, March 3, 2012, London, UK|publisher=[[SRI International]] Computer Science Laboratory|last3=Woodruff|first3=Jonathan|last4=Anderson|first4=Jonathan|last5=Anderson|first5=Ross|author-link5=Ross J. Anderson|last6=Dave|first6=Nirav|last7=Laurie|first7=Ben|author-link7=Ben Laurie|last8=Moore|first8=Simon W.|last9=Murdoch|first9=Steven J.|author-link9=Steven Murdoch|first10=Philip|last10=Paeps|first11=Michael|last11=Roe|first12=Hassen|last12=Saidi}}</ref>

* [[SHA-256]] hash function.

* [[Smart contract]]s use 256- or 257-bit integers; 256-bit words for the [[Ethereum Virtual Machine]]. "We realize that a 257 bits byte is quite unusual, but for smart contracts it is ok to have at least 256 bits numbers. The leading VM for smart contracts, Ethereum VM, introduced this practice and other blockchain VMs followed."<ref>{{Cite web|first=Dmitriy |last=Borisenkov |date=23 October 2019|title=[llvm-dev] RFC: On non 8-bit bytes and the target for it|url=https://lists.llvm.org/pipermail/llvm-dev/2019-October/136115.html|access-date=2021-09-11}}</ref>