Editing Cyclic redundancy check (section)

{{Short description|Error-detecting code for detecting data changes}}
{{Use dmy dates|date=October 2023}}

A '''cyclic redundancy check''' ('''CRC''') is an [[Error correcting code|error-detecting code]] commonly used in digital [[Telecommunications network|networks]] and storage devices to detect accidental changes to digital data. Blocks of data entering these systems get a short ''check value'' attached, based on the remainder of a [[Polynomial long division|polynomial division]] of their contents. On retrieval, the calculation is repeated and, in the event the check values do not match, corrective action can be taken against data corruption. CRCs can be used for [[Error detection and correction|error correction]] (see [[Mathematics of cyclic redundancy checks#Bitfilters|bitfilters]]).<ref>{{cite web|url=http://www.drdobbs.com/an-algorithm-for-error-correcting-cyclic/184401662|title=An Algorithm for Error Correcting Cyclic Redundance Checks|website=drdobbs.com|access-date=28 June 2017|archive-url=https://web.archive.org/web/20170720165847/http://www.drdobbs.com/an-algorithm-for-error-correcting-cyclic/184401662|archive-date=20 July 2017|url-status=dead}}</ref>

CRCs are so called because the ''check'' (data verification) value is a ''redundancy'' (it expands the message without adding [[Entropy (information theory)|information]]) and the [[algorithm]] is based on [[Cyclic code|''cyclic'' codes]]. CRCs are popular because they are simple to implement in binary [[Computer hardware|hardware]], easy to analyze mathematically, and particularly good at detecting common errors caused by [[Noise (electronics)|noise]] in transmission channels.  Because the check value has a fixed length, the [[Function (mathematics)|function]] that generates it is occasionally used as a [[hash function]].