# Questions tagged [crc]

CRC stands for a Cyclic Redundancy Check, a method to verify the integrity of information, and detect errors in storage and communication.

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### Calculate the probability of undetected errors for the whole file (not packets) in the CRCs

If we have a large file, I want to know how this will affect the probability of undetected errors, especially in CRCs. I know that undetected error rate (packet or chunk) is BitR * BER * 0.5k where k ...
32 views

### Understanding a CRC32 Implementation

I'm currently trying to understand an implementation of CRC32 about which I have a question. On this page at section 6, there is the following code: ...
35 views

### Understanding CRC Computation with PCLMULQDQ

I am currently reading this paper which shows how to calculate CRC using the instruction PCLMULQDQ. I don't quite understand the equations in it yet. Starting with this one for the definition of ...
21 views

### Why frame must be longer than generator polynomial?

Here is an excerpt from Andrew S. Tanenbaum, Computer Networks, 5th edition, Chapter 3 (The data link layer), Page 213: When the polynomial code method is employed, the sender and receiver must ...
27 views

### Question on crc32 -> 64 by multiplication

Having a hash quickly accessible in a large database is a good thing, most hashes these days are much too large for that. Best performance on a database is 32 bit int followed not too far off by 64 ...
81 views

### Why does $x^{15}+x^{14}+1$ detect all errors at most 32768 bits apart?

Reference Question from Forouzon Book Computer Network. Find the status of the following generator related to two isolated, single-bit errors. $$x^{15} + x^{14} + 1$$ Answer given : This polynomial ...
462 views

### Replacing 0x1021 polynomial with 0x8005 in this CRC-16 code

I have some highly optimized code for a CRC-16 implementation. It focuses on speed rather than flexibility, and as a result, it is hard-coded to model the specific unreflected polynomial ...
62 views

### using 2 short CRC(s) VS one longer CRC

I'm doing some research on the CRCs, but i can't find informations about the use of two (or more) short CRCs compared to the use of a longer CRC: Suppose that i have a dataword A of some length and 3 ...
69 views

### How to understand the CRC Algorithm from the CAN specification?

I am trying to understand how the cyclic redundancy check (CRC) algorithm from the Controller Area Network (CAN) specification works. Here is the pseudocode. ...
234 views

### CRC computation speed vs polynomials features

I tried to find information about how features of a CRC polynomials influence computation speed of implementations. It is obvious that (depending from the CPU architecture the algorithm runs on) ...
227 views

### Can one quickly update CRC codes based on small change and previous CRC code?

I asked this on StackOverflow, but, alas, no answers. I'd like to use CRC or similar codes to check whether certain very large objects are likely to be identical. The trouble is, small parts of these ...
18 views

### custom cc 16 bits with Polynomial and Initial Value , algorithm

I generate crc 16 bits with hex Workshop. Polynomial :1234(hex) Initial Value :5678 (hex) . making it on 010 (ascii) and get 3744. I looking for this algorithm , I prefer it on c#. but I not find it....
131 views

### How to handle generator polynomial in CRC if given in (x+1) (x^3+ x^2 +1) form?

I am trying to find the frame check sequence in cyclic redundancy check(CRC). Given that the generator polynomial is $\ g(x)= (x+1)(x^3 + x^2 + 1)$. Let's say the data sequence is $\ 10110001$. In ...
141 views

### CRC: false positive under some circumstances

Consider two computers $A$ and $B$. $A$ uses $G$ and $B$ uses $G'$ for the CRC computation. It is given that $\deg G \ne \deg G'$. Computer $A$ wants to send a data $D$. The claim says that: There ...
747 views

### What is the error-detection-probability of CRC

I have a table which stores all serial numbers of devices in my system: ...
22 views

### How to derive an algorithms that generates check sums [closed]

Column S contains the check sums of the values given in columns R and Xc. Does anyone here have an idea about how to find the corresponding algorithm to calculate the check sums? Thanks in advance <...
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### Numerically validate CRC performance

Koopman, P., & Chakravarty, T. (2004, June). Cyclic redundancy code (CRC) polynomial selection for embedded networks. In Dependable Systems and Networks, 2004 International Conference on (pp. 145-...
4k views

### Polynomial generator required to detect single bit error in Cyclic Redundancy Check codes

I was reading about CRC coding from two books: Data Communication and Networking by Forouzan Page 294 Computer Network by Tanenbaum Page 188 They use following notations: $d(x)$: dataword to be ...
86 views

### Protecting data unequally using Error Correction Codes

Say I'd like to transmit a 100-bit packet which has a field containing a continuous value. I'd like to protect this value with an error correction code but an error in the MSB of this value is much ...
109 views

### CRC error detection

I know that to find an error in signal we have to divide given signal with given polynomial and if 0 remains there is no error. But if I have received signal: 0000 0101 0101 0000 1010 0101 and ...
137 views

### Check if a given polynomial is primitive

I try to estimate error detection capabilities of arbitrary CRC polynomials. One important criteria is if a given polynomial is primitive. So I need an algorithm to check that. My goal is to write a C ...
594 views

### How do I compute a “CRC code word” from an information word and CRC polynomial?

I have the CRC polynomial 1101, and my information word is 10001111. How do I find the CRC code word? Disclaimer: This is an assignment problem. I'd appreciate any help, particularly solving the ...
146 views

### Cyclic Redundancy Check Codewords Finding the Original Message

So I have the received transmitted message in polynomial form as $$T'(X) = X^{15}+X^{13}+X^8+X^7+X^4+X^3$$ and the error polynomial as $$E(X) = X^{16}+X^{13}+X^3$$ and the generator polynomial as ...
739 views

### Correcting two-bit error using a CRC

What algorithm can be used to correct a two-bit error in a message protected by a 32-bit CRC, assuming the CRC polynomial allows that? I'm seeking something for 480-bit payload, able to detect ...
What is the range of “the” CRC-32, the one used by Unix, Ethernet, zip, and many other industrial standards? Mathematically, a CRC is defined as follows: let $G$ be the CRC polynomial in \$\mathbb{F}...