Key clustering: Difference between revisions

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{{Multiple issues|

== Key Clustering ==

{{Refimprove|date=November 2019}}

{{Confusing|date=June 2020}}

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Key or [[hash function]] should avoid ''[[Hash table|clustering]]'', the mapping of two or more keys to consecutive slots. Such clustering may cause the lookup cost to skyrocket, even if the load factor is low and [[hash collision|collisions]] are infrequent. The popular multiplicative hash<ref>{{cite book | first=Donald |last=Knuth |author1-link=Donald Knuth | title = The Art of Computer Programming | volume = 3: ''Sorting and Searching'' | edition = 2nd | publisher = Addison-Wesley | year = 1998 | isbn = 978-0-201-89685-5 | pages = 513–558 }} {{verify source |date=September 2019 |reason=This ref was deleted Special:Diff/902760856 by a bug in VisualEditor and later restored by a bot from the original cite located at Special:Permalink/895004660 cite #3 - verify the cite is accurate and delete this template. [[User:GreenC bot/Job 18]]}}</ref> is claimed to have particularly poor clustering behaviour.<ref>{{Cite web|title = Prime Double Hash Table|url = https://www.concentric.net/~Ttwang/tech/primehash.htm|date = March 1997|accessdate = 2015-05-10|last = Wang|first = Thomas|archiveurl = https://web.archive.org/web/19990903133921/http://www.concentric.net/~Ttwang/tech/primehash.htm|archivedate = 1999-09-03}} {{verify source |date=September 2019 |reason=This ref was deleted Special:Diff/902760856 by a bug in VisualEditor and later restored by a bot from the original cite located at Special:Permalink/895004660 cite #9 - verify the cite is accurate and delete this template. [[User:GreenC bot/Job 18]]}}</ref>

==References==

[[Ciphertext]] is the result of encrypting [[plaintext]] using a key. [[Ciphers]] (or [[algorithms]]) are used to [[encrypt]] the [[plaintext]] using keys. A good [[algorithm]], using different keys on the same [[plaintext]] generates a different [[ciphertext]], irrespective of the key length.

{{Reflist}}

[[Category:CryptographyKey management]]

Let us assume that I have a [[plaintext]] P, two keys (of same length, assumed for simplicity) K1 and K2, and an [[algorithm]] A. I will generate [[ciphertexts]] C1 and C2 with the two keys as follows

P -----A(K1)------> C1

{{crypto-stub}}

P -----A(K2)------> C2

This might not always be the case. I could have possibly gotten C1 [[ciphertext]] in Case 2 as well. That would be '''Key Clustering'''.

For the sake of definition, key clustering is when two different keys generate the same ciphertext from the same plaintext, using same or different algorithm.

[[Category:Cryptography]]