Editing Key (cryptography) (section)

== Key sizes ==
{{main|Key size}}

[[Key size]] is the number of [[bit]]s in the key defined by the algorithm. This size defines the upper bound of the cryptographic algorithm's security.<ref>{{Cite web|title=What is Key Length? - Definition from Techopedia|url=http://www.techopedia.com/definition/3999/key-length|access-date=2021-05-01|website=Techopedia.com|date=16 November 2011 |language=en}}</ref> The larger the key size, the longer it will take before the key is compromised by a brute force attack. Since perfect secrecy is not feasible for key algorithms, researches are now more focused on computational security.

In the past, keys were required to be a minimum of 40 bits in length, however, as technology advanced, these keys were being broken quicker and quicker. As a response, restrictions on symmetric keys were enhanced to be greater in size.

Currently, 2048 bit [[RSA (cryptosystem)|RSA]]<ref>{{Cite journal|last=Hellman|first=Martin|title=An Overview of Public Key Cryptography|url=https://netlab.ulusofona.pt/im/teoricas/OverviewPublicKeyCryptography.pdf|journal=IEEE Communications Magazine}}</ref> is commonly used, which is sufficient for current systems. However, current RSA key sizes would all be cracked quickly with a powerful quantum computer.<ref>{{Cite web |date=2024-08-23 |title=Toward a code-breaking quantum computer |url=https://news.mit.edu/2024/toward-code-breaking-quantum-computer-0823 |access-date=2025-05-14 |website=MIT News {{!}} Massachusetts Institute of Technology |language=en}}</ref>

"The keys used in public key cryptography have some mathematical structure. For example, public keys used in the RSA system are the product of two prime numbers. Thus public key systems require longer key lengths than symmetric systems for an equivalent level of security. 3072 bits is the suggested key length for systems based on factoring and integer discrete logarithms which aim to have security equivalent to a 128 bit symmetric cipher."<ref>{{Cite web|date=2013-05-27|title=Anatomy of a change – Google announces it will double its SSL key sizes|archive-url=https://web.archive.org/web/20230908035830/https://nakedsecurity.sophos.com/2013/05/27/anatomy-of-a-change-google-announces-it-will-double-its-ssl-key-sizes/ |archive-date=8 September 2023|url=https://nakedsecurity.sophos.com/2013/05/27/anatomy-of-a-change-google-announces-it-will-double-its-ssl-key-sizes/|access-date=2021-04-09|website=Naked Security|language=en-US}}</ref>