Editing Encryption (section)

== Encryption in cryptography ==

In the context of cryptography, encryption serves as a mechanism to ensure [[Information security|confidentiality]].<ref name=":1"/> Since data may be visible on the Internet, sensitive information such as [[password]]s and personal communication may be exposed to potential [[Eavesdropping|interceptors]].<ref name=":1" /> The process of encrypting and decrypting messages involves [[Key (cryptography)|keys]]. The two main types of keys in cryptographic systems are symmetric-key and public-key (also known as asymmetric-key).<ref name=":0">{{cite book |doi=10.1016/B978-0-12-802324-2.00011-7 |chapter=Security Component Fundamentals for Assessment |title=Security Controls Evaluation, Testing, and Assessment Handbook |date=2016 |last1=Johnson |first1=Leighton |pages=531–627 |isbn=978-0-12-802324-2 }}</ref><ref name=":2">{{Cite web|last=Stubbs|first=Rob|title=Classification of Cryptographic Keys|url=https://www.cryptomathic.com/news-events/blog/classification-of-cryptographic-keys-functions-and-properties|access-date=2021-02-03|website=www.cryptomathic.com|language=en-us}}</ref>

Many complex cryptographic algorithms often use simple [[modular arithmetic]] in their implementations.<ref>{{Cite web|title=Chapter 3. Modular Arithmetic|url=https://www.doc.ic.ac.uk/~mrh/330tutor/ch03.html|access-date=2021-08-15|website=www.doc.ic.ac.uk|archive-date=2021-10-11|archive-url=https://web.archive.org/web/20211011110748/https://www.doc.ic.ac.uk/~mrh/330tutor/ch03.html|url-status=dead}}</ref>

===Types===

In [[Symmetric-key algorithm|symmetric-key]] schemes,<ref>{{Cite web|url=https://iaktueller.de/Collatz.py|title=Symmetric-key encryption software|access-date=2022-02-15|archive-date=2022-03-10|archive-url=https://web.archive.org/web/20220310103427/http://iaktueller.de/Collatz.py|url-status=dead}}</ref> the encryption and decryption keys are the same. Communicating parties must have the same key in order to achieve secure communication. The German Enigma Machine used a new symmetric-key each day for encoding and decoding messages.

In [[public-key cryptography]] schemes, the encryption key is published for anyone to use and encrypt messages. However, only the receiving party has access to the decryption key that enables messages to be read.<ref>Bellare, Mihir. "Public-Key Encryption in a Multi-user Setting: Security Proofs and Improvements." Springer Berlin Heidelberg, 2000. p. 1.</ref> Public-key encryption was first described in a secret document in 1973;<ref>{{cite web|url=https://www.gchq.gov.uk/history/pke.html|archive-url=https://web.archive.org/web/20100519084635/https://www.gchq.gov.uk/history/pke.html|title=Public-Key Encryption – how GCHQ got there first!|publisher=gchq.gov.uk|archive-date=May 19, 2010}}</ref> beforehand, all encryption schemes were symmetric-key (also called private-key).<ref name="Goldreich">[[Oded Goldreich|Goldreich, Oded.]] Foundations of Cryptography: Volume 2, Basic Applications. Vol. 2. Cambridge university press, 2004.</ref>{{rp|478}} Although published subsequently, the work of Diffie and Hellman was published in a journal with a large readership, and the value of the methodology was explicitly described.<ref>{{citation | first1=Whitfield | last1=Diffie | first2=Martin | last2=Hellman | title=New directions in cryptography| pages=644–654| publisher=IEEE transactions on Information Theory| volume=22 | date=1976 }}</ref> The method became known as the [[Diffie–Hellman key exchange|Diffie-Hellman key exchange]].

[[RSA (cryptosystem)|RSA (Rivest–Shamir–Adleman)]] is another notable public-key [[cryptosystem]]. Created in 1978, it is still used today for applications involving [[digital signature]]s.<ref>{{Cite web |last=Kelly |first=Maria |date=December 7, 2009 |title=The RSA Algorithm: A Mathematical History of the Ubiquitous Cryptological Algorithm |url=https://www.sccs.swarthmore.edu/users/10/mkelly1/rsa.pdf |access-date=March 30, 2022 |website=Swarthmore College Computer Society |archive-date=March 31, 2022 |archive-url=https://web.archive.org/web/20220331215424/https://www.sccs.swarthmore.edu/users/10/mkelly1/rsa.pdf |url-status=dead }}</ref> Using [[number theory]], the RSA algorithm selects two [[prime number]]s, which help generate both the encryption and decryption keys.<ref>{{cite journal |last1=Prasetyo |first1=Deny |last2=Widianto |first2=Eko Didik |last3=Indasari |first3=Ike Pratiwi |title=Short Message Service Encoding Using the Rivest-Shamir-Adleman Algorithm |journal=Jurnal Online Informatika |date=6 September 2019 |volume=4 |issue=1 |pages=39 |doi=10.15575/join.v4i1.264 |doi-access=free }}</ref>

A publicly available public-key encryption application called [[Pretty Good Privacy]] (PGP) was written in 1991 by [[Phil Zimmermann]], and distributed free of charge with source code. PGP was purchased by [[NortonLifeLock|Symantec]] in 2010 and is regularly updated.<ref>{{Cite web|url=https://www.computerworld.com/article/2517739/symantec-buys-encryption-specialist-pgp-for--300m.html|title=Symantec buys encryption specialist PGP for $300M|first=Jeremy|last=Kirk|date=April 29, 2010|website=Computerworld|access-date=January 31, 2020|archive-date=January 31, 2020|archive-url=https://web.archive.org/web/20200131201636/https://www.computerworld.com/article/2517739/symantec-buys-encryption-specialist-pgp-for--300m.html|url-status=dead}}</ref>