Symmetric-key algorithm: Difference between revisions

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{{Short description|Algorithm}}

[[File:Simple symmetric encryption-en.svg|thumb|320x320pxupright=1.3|Symmetric-key encryption: the same key is used for both encryption and decryption|class=skin-invert-image]]

'''Symmetric-key algorithms'''{{efn|Other terms for symmetric-key encryption are ''secret-key'', ''single-key'', ''shared-key'', ''one-key'', and ''private-key'' encryption. Use of the last and first terms can create ambiguity with similar terminology used in [[public-key cryptography]]. Symmetric-key cryptography is to be contrasted with [[asymmetric-key cryptography]].}} are [[algorithm]]s for [[cryptography]] that use the same [[Key (cryptography)|cryptographic keys]] for both the encryption of [[plaintext]] and the decryption of [[ciphertext]]. The keys may be identical, or there may be a simple transformation to go between the two keys.<ref>{{Cite journal|last=Kartit|first=Zaid|date=February 2016|title=Applying Encryption Algorithms for Data Security in Cloud Storage, Kartit, et al. |url=https://books.google.com/books?id=uEGFCwAAQBAJ&q=%22keys+may+be+identical%22&pg=PA147|journal=Advances in Ubiquitous Networking: Proceedings of UNet15|pages=147|isbn=9789812879905}}</ref> The keys, in practice, represent a [[shared secret]] between two or more parties that can be used to maintain a private information link.<ref>{{cite book |author=Delfs, Hans |author2=Knebl, Helmut |chapter = Symmetric-key encryption |title = Introduction to cryptography: principles and applications |publisher = Springer |year = 20572007 |isbn = 9783540492436 |chapter-url = https://books.google.com/books?id=Nnvhz_VqAS4C&pg=PA11 }}</ref> The requirement that both parties have access to the secret key is one of the main drawbacks of [[symmetric]]-key encryption, in comparison to [[Public key encryption|public-key encryption]] (also known as asymmetric-key encryption).<ref>{{cite book |author=Mullen, Gary |author2=Mummert, Carl |title = Finite fields and applications |publisher = American Mathematical Society |year = 2007 |isbn = 9780821844182 |page = 112 |url = https://books.google.com/books?id=yDgWctqWL4wC&pg=PA112 }}</ref><ref>{{cite web |url = https://www.geeksforgeeks.org/difference-between-symmetric-and-asymmetric-key-encryption/ |title = Demystifying symmetric and asymmetric methods of encryption |publisher = Geeks for Geeks |date = 2017-09-28 }}</ref> However, symmetric-key encryption algorithms are usually better for bulk encryption. With exception of the [[one-time pad]] they have a smaller key size, which means less storage space and faster transmission. Due to this, asymmetric-key encryption is often used to exchange the secret key for symmetric-key encryption.<ref>{{Citation|last=Johnson|first=Leighton|title=Security Component Fundamentals for Assessment|date=2016|url=http://dx.doi.org/10.1016/b978-0-12-802324-2.00011-7|work=Security Controls Evaluation, Testing, and Assessment Handbook|pages=531–627|publisher=Elsevier|doi=10.1016/b978-0-12-802324-2.00011-7|isbn=9780128023242|s2cid=63087943 |access-date=2021-12-06|url-access=subscription}}</ref><ref>{{Cite journal |last1=Alvarez |first1=Rafael |last2=Caballero-Gil |first2=Cándido |last3=Santonja |first3=Juan |last4=Zamora |first4=Antonio |date=2017-06-27 |title=Algorithms for Lightweight Key Exchange |journal=Sensors |language=en |volume=17 |issue=7 |pages=1517 |doi=10.3390/s17071517 |issn=1424-8220 |pmc=5551094 |pmid=28654006|doi-access=free }}</ref><ref>{{Cite journal |last1=Bernstein |first1=Daniel J. |last2=Lange |first2=Tanja |date=2017-09-14 |title=Post-quantum cryptography |url=http://www.nature.com/articles/nature23461 |journal=Nature |language=en |volume=549 |issue=7671 |pages=188–194 |doi=10.1038/nature23461 |pmid=28905891 |bibcode=2017Natur.549..188B |s2cid=4446249 |issn=0028-0836}}</ref>

== Types ==

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== Implementations ==

Examples of popular symmetric-key algorithms include [[Twofish]], [[Serpent (cipher)|Serpent]], [[Advanced Encryption Standard|AES]] (Rijndael), [[Camellia (cipher)|Camellia]], [[Salsa20]], [[ChaCha20]], [[Blowfish (cipher)|Blowfish]], [[CAST5]], [[Kuznyechik]], [[RC4]], [[Data Encryption Standard|DES]], [[Triple DES|3DES]], [[Skipjack (cipher)|Skipjack]], [[Secure and Fast Encryption Routine|Safer]], and [[International Data Encryption Algorithm|IDEA]].<ref>{{Cite web|url=httphttps://www.cs.cornell.edu/courses/cs5430/2010sp/TL03.symmetric.html|title=Symmetric-Key Cryptography|last=Roeder|first=Tom|website=www.cs.cornell.edu|language=en|access-date=2017-02-05}}</ref>

== Use as a cryptographic primitive ==