Does anyone have CRC128 and CRC256 Code in C++ and C#?

Question

I am learning, trying to get thoughts behind CRC. I can't find CRC128 and CRC256 code anywhere. If anyone of you have the C++ or C# Code for them, please share them with me. Also provide online links to the websites. I am a newbie and can't code it by myself at all, neither can convert theories and mathematics to the coding. So I ask for help from you. It will be so nice of you who provide me the proper and simple codes. If anyone provides me these codes, please do also provide CRC Table generator functions. Thank you.

Answer 1

I agree with you except that the accidental collision rate is higher than 1 in 2^32 or 1 in 2^64 for 32 bit and 64 bit CRCs respectively.

I wrote an app that kept track of things by their CRC values for tracking items. We needed to track potentially millions of items and we started with a CRC32 which in real world practice has a collision rate of around 1 in 2^16 which was an unpleasant surprise. We then re-coded to use a CRC64 which had a real world collision rate of about 1 in 2^23. We tested this after the unpleasant surprise of the 32 bit one we started with and accepted the small error rate of the 64 bit one.

I can't really explain the statistics behind the expected collision rate but it makes sense that you would experience a collision much sooner that the width of the bits. Just like a hashtable...some hash buckets are empty and others have more than one entry....

Even for a 256 bit CRC the first 2 CRC's could be the same...it would be almost incredible but possible.