Editing Salt (cryptography) (section)

{{Short description|Random data used as an additional input to a hash function}}
{{other uses|Salt (disambiguation)}}

In [[cryptography]], a '''salt''' is [[Random Number Generator|random]] data fed as an additional input to a [[one-way function]] that [[Cryptographic hash function|hashes]] [[Data (computing)|data]], a [[password]] or [[passphrase]].<ref>{{Cite web |last1=Fenton |first1=James L. |last2=Grassi |first2=Paul A. |last3=Garcia |first3=Michael E. |date=June 2017 |title=NIST Special Publication 800-63-3 |url=https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-63-3.pdf |website=NIST Technical Series Publications}}</ref> Salting helps defend against attacks that use precomputed tables (e.g. [[rainbow tables]]), by vastly growing the size of table needed for a successful attack.<ref>{{Cite book |last=Anderson |first=Ross |title=Security engineering: a guide to building dependable distributed systems |date=2020 |isbn=978-1-119-64281-7 |edition=Third |location=Indianapolis, Indiana |oclc=1224516855}}</ref><ref>{{Cite web |last=Godwin |first=Anthony |date=10 September 2021 |title=Passwords Matter |url=http://bugcharmer.blogspot.com/2012/06/passwords-matter.html |access-date=2016-12-09 |website=The Bug Charmer |type=Blog}}</ref><ref>{{Cite book |last1=Boneh |first1=Dan |url=https://crypto.stanford.edu/~dabo/cryptobook/BonehShoup_0_5.pdf |title=A Graduate Course in Applied Cryptography |last2=Shoup |first2=Victor |date=January 4, 2020 |pages=693–695}}</ref> It also helps protect passwords that occur multiple times in a database, as a new salt is used for each password instance.<ref name=":0" /> Additionally, salting does not place any burden on users. 

Typically, a unique salt is randomly generated for each password. The salt and the password (or its version after [[key stretching]]) are [[concatenation|concatenated]] and fed to a [[cryptographic hash function]], and the output [[Hash function|hash value]] is then stored with the salt in a database. The salt does not need to be encrypted, because knowing the salt would not help the attacker.<ref name=":0">{{Cite book |last=Rosulek |first=Mike |title=The Joy of Cryptography |date=January 3, 2021 |pages=204–205 |chapter=Chapter 11: Hash Functions |chapter-url=https://joyofcryptography.com/pdf/chap11.pdf}}</ref>

Salting is broadly used in cybersecurity, from [[Unix]] system credentials to [[Internet security]].

Salts are related to [[cryptographic nonce|cryptographic nonces]].