Talk:Cyclic redundancy check

message: It would be nice if the official IV, if any, was listed for each of these polynomials. I think most just start with all-1s, but there may be exceptions. 75.145.68.90 (talk) 00:05, 25 May 2018 (UTC)
thread_title: Initial Value

message: Merge
*Mathematics of cyclic redundancy checks
*Computation of cyclic redundancy checks
These articles overlap with the contents of this article, some information is duplicated some elements are better presented in the linked articles.  — Preceding unsigned comment added by 142.58.211.180 (talk) 23:15, 22 March 2016 (UTC)
replies: text: Agreed, dividing the pages only adds confusion, at the very least the mathematics and computation articles should be merged, and the resulting article added as a reference to the main CRC article.68.36.129.21 (talk) 07:13, 4 January 2017 (UTC)

text: Oppose merge: my feeling is that the distinct mathematics and computation pages are highly technical, and the current structure of a summary on the Cyclic redundancy check page links appropriately with a template:main (as it currently is) is a good structure that is better not tampered with. Klbrain (talk) 14:23, 21 March 2018 (UTC)

text: Oppose merge: I agree with Klbrain. The reference information specific to CRC here is a lot of the article. 75.145.68.90 (talk) 00:05, 25 May 2018 (UTC)
thread_title: Merger Discussion

message: I think the table should be made slimmer, as it is not very nice to have a wikipage with a scrollbar in the bottom of the screen (unlike [most?] other wikipages). Just my two dimes.
// Ilyushin
:Agree It's probably non-breaking spaces in the <math> elements; any suggestions? – Regregex (talk) 17:45, 28 September 2009 (UTC)
thread_title:  Page too wide 

message: Not my area but the phrase "the number of the highest nonzero coefficient" makes no sense to me.  Could it have meant "the highest exponent with nonzero coefficient" ?--Billymac00 (talk) 04:15, 10 March 2010 (UTC)
thread_title:  Correct wording? 

message: Till editing this article, I had no idea "CRC" had any cryptological significance. It's an encoding system but since everyone must agree on the exact method used, it offers no protection from interception or spoofing by Carol. I thought CRCs were only useful in fighting channel noise. So, I don't think the "insecurity" of a CRC function is something to dwell on in the lead since no-one expects it to provide security in the first place. --Wtshymanski (talk) 14:07, 10 November 2010 (UTC)
replies: text: The problem is that people think they can use it for purposes that actually demand cryptographically secure functions. What means for a function to be secure depends on the context. If you want good protection against random channel errors a cryptographic hash function is actually more "secure" than a CRC. But neither CRCs nor unkeyed hash functions can protect against malicious modification of data. So yes, CRCs are only useful for fighting channel noise, and saying that it is a "insecure" function in the lead would be quite misleading in this regard. Nageh (talk) 14:42, 10 November 2010 (UTC)
replies: text: Fair enough. – Regregex (talk) 20:23, 10 November 2010 (UTC)

text: Cryptographic hashes are not more secure against random noise than CRCs, because they do not guarantee a minimum distance between code words for adjacent data words.  The best known 32-bit CRC codes are proven to detect up to five individual bit errors and bursts of up to 32 bits in code words of up to 5,275 bits (Castagnoli, 1993).  DES (talk) 06:39, 15 February 2011 (UTC)
thread_title: In over my head

message: I'm sorry, but I'm kind of lost with these terms. Why couldn't we say for example that for the value :
x^{4} + x + 1 we could use the representation 0x13 (0010 0011) instead of those cryptic 0x3 / 0xC / 0x9 ?
Or at least explain what is the meaning of those values.  —Preceding unsigned comment added by Glatapoui (talk • contribs) 10:11, 23 November 2010 (UTC)
replies: text: I've added a paragraph to the section Specification of CRC in the article to explain the triplets.  The high-order bit is left off for reasons explained in that section; there's a hatnote on the table as a reminder. HTH.  – Regregex (talk) 17:04, 23 November 2010 (UTC)
thread_title:  Representations: normal / reversed / reverse of reciprocal ? 

message: This article was mixed with math and it is too complicated. The animated gifs are too speedy to follow. Much interest was granted to text and explanation but the example is very poor and it is not ilustrated.  —Preceding unsigned comment added by 212.77.163.101 (talk) 12:51, 4 March 2011 (UTC)
thread_title:  Too complicated for wikipedia level 

message: there should be a link to a utility to calculate crc32 hash of files  — Preceding unsigned comment added by 82.139.86.184 (talk) 13:48, 5 June 2011 (UTC)
thread_title:  utility 

message: I think there may be a typo in the CRC32C polynomial in the table, I think one of the columns disagrees with one of the other columns, but my polynomial math is too rusty to be sure, so I have not edited it.  Would someone more experienced please check and update the article if necessary?
90.184.113.110 (talk) 15:37, 7 May 2012 (UTC)
replies: text: I don't see any error.  The first hex representation is as it appears in RFC 3720 (less the leading 1 as described above the table) and the Koopman notation is as printed in the citation.  I've just checked that the algebraic form corresponds to the hex constant in the RFC.  re/greg/ex;{mbox|history} 17:05, 8 May 2012 (UTC)
thread_title:  Possible typo in the CRC32C polynomial 

message: I printed this article with others in a PediaPress paper book on 7th December.  Although no edits have been made to the example in Computation of CRC, and although the alignment is correct in the wiki source, the printed book has an alignment problem where rows appear shifted left or right by one or more characters.
It makes the example needlessly difficult to follow, as you'd expect, but I have no idea why the printed version doesn't preserve the alignment.
Ecashin (talk) 03:25, 24 December 2012 (UTC)
thread_title:  fixed-width text alignment not preserved in PediaPress book 

message: THIS table is currently missing CRC13  used by the BBC Longwave transmitter on 198khz.  
Eyreland (talk) 03:35, 27 September 2013 (UTC)
thread_title:  Missing CRCs 

message: This article is not necessarily true. All CRCs are not calculated values (let alone polynomials). For example, some old file systems has CRCs that were simply known values that served as simple checks that the disk was being correctly read. Common values were 0xA5 and 0x55 (looking at the bit patterns will tell you why). CRCs are simply known, repeatable values. How/if they are calculated is irrelevant.  — Preceding unsigned comment added by 74.67.119.190 (talk) 14:32, 15 August 2014 (UTC)
replies: text: Is there a source that describes this type and usage of CRC? ~KvnG 13:36, 3 September 2014 (UTC)
replies: text: None I can think of that Wikipedia would accept as a source, but one that comes to mind are the various disk formats used on old microcomputers, such as the TRS-80. The format used for TRS-80 floppy disks had two constants values, called CRCs, that could have checked for consistency. I don't remember if they were per track, sector, et. al. FAT does something similar, but I don't think MS called them CRCs.  — Preceding unsigned comment added by 74.67.119.190 (talk) 15:08, 2 November 2014 (UTC)

text: All Cyclic Redundancy Checks *are* calculated values using polynomials.  Your statement accusing this article of not being necessarily true is "All CRCs are not calculated values (let alone polynomials)." However, the article is titled "Cyclic redundancy check", not "CRC".  The TLA "CRC" has many uses as can be seen in the disambiguation page CRC; perhaps what you are referring to is yet another thing called a "CRC". Vincent J. Lipsio (talk) 18:56, 2 November 2014 (UTC)

text: This seems to indicate that the TRS-80 used calculated CRC values. ~KvnG 15:26, 7 November 2014 (UTC)
thread_title:  Actual Meaning of CRC 

message: In an effort to do some copyediting of this article, I found that all of the links targeting sections within the article point to sections that no longer exist. Specifically, these links:
Computation
integer encodings
table
The link to #Computation of CRC now obviously points to its own article, Computation of cyclic redundancy checks, so I explicitly edited this. However, the other links may need to be looked at by someone with expertise in this area, to establish exactly where they are meant to link to. - Alistairirvine (talk) 21:17, 27 August 2014 (UTC)
thread_title:  Links to sections that no longer exist 

message: The article does not even mention Fletcher's checksum and Adler-32.Sure, those are not CRCs, but it is important to understand the relation and the differences. Please add information about that to the article. --rtc (talk) 20:14, 17 June 2017 (UTC)
thread_title:  Missing information 

message: "and will detect a fraction 1/(1 − 2^−n) of all longer error bursts." -- This cannot be correct. For example, with a 3 bit crc, 2^-3 = 1/8.
1/(1-1/8) == 8/7.  How do you detect 8/7 of all longer bursts?  This value should never be greater than 1. 24.180.6.18 (talk) 16:45, 4 August 2017 (UTC)
replies: text: – I see that this was corrected not long after this was posted.  —Quondum 21:21, 18 August 2018 (UTC)
thread_title:  bad math 

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thread_title:  External links modified 

message: There are nice examples in many programming languages at Rosetta Code  — Preceding unsigned comment added by 148.163.178.15 (talk) 20:43, 21 August 2019 (UTC)
thread_title:  Examples 

message: The algorithm presented is one that hides much of the actual computation by using a lookup table.  The algorithm isn't presented as a practical implementation I assume, but rather as clarification of the steps in the computation.  I think it would be better if the algorithm provided here was one calculating the CRC32 one bit at a time.  This would help clarify the functionality of the CRC32.  Memoization is a way of optimizing the speed of an implementation, one of many, and complicates the algorithm.  If the purpose of this section is to illustrate speed up techniques, then the section should be described as such and expanded.  I would be happy to replace this example or add to this example with a one bit at a time algorithm.  Gnuarm (talk) 15:43, 5 December 2020 (UTC)
replies: text: Don't replace, two CRC-32 algorithm examples would be better.  If you add an example, it should be similar to how the other one is shown.  • Sbmeirow • Talk • 20:32, 5 December 2020 (UTC)
thread_title: CRC-32 Algorithm