Luhn algorithm: Difference between revisions

Revision as of 09:17, 20 July 2025

Latest revision as of 14:34, 7 August 2025

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{{Short description|Simple checksum formula}}

{{redirects|Luhn|people named Luhn|Luhn (surname)}}

The '''Luhn algorithm''' or '''Luhn formula''' (creator: [[IBM]] scientist [[Hans Peter Luhn]]), also known as the "[[modular arithmetic|modulus]] 10" or "mod 10" [[algorithm]], is a simple [[check digit]] formula used to validate a variety of identification numbers. {{efn|It is described in [[United States|US]] patent 2950048A, granted on {{date|1960-08-23|DMY}}.<ref name="US2950048A">{{cite patent|title=Computer for Verifying Numbers|country=US|number=2950048A|status=patent|pubdate={{date|1960-08-23|DMY}}|gdate={{date|1960-08-23|DMY}}|invent1=Luhn|inventor1-first=Hans Peter|fdate=1954-01-06|inventorlink=Hans Peter Luhn}}</ref>}}

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parity := length mod 2

'''for''' i from 1 to (length - 1) '''do'''

'''if''' i mod 2 !== parity '''then'''

sum := sum + cardNumber[i]

'''elseif''' cardNumber[i] > 4 '''then'''

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* [[South Africa|South African]] ID numbers

* [[South Africa|South African]] Tax reference numbers

* [[Personal identity number (Sweden)| Swedish]] [[nationalPersonal identificationidentity numbers number]]s

* [[Sweden|Swedish]] Corporate Identity Numbers (OrgNr)

* [[Greece|Greek]] Social Security Numbers (ΑΜΚΑ)