I am making an library that parses torrent names, but I cannot find name for these 8-digit hex numbers. I have never seen them outside anime community, but aren't they some ancient method to check the validity of the file?
Checksums.
>>>>>>>>/a/
>>54921881
Yeah, but there was some specific name for it with a three letter abbreviation. Circular *something* Check or something.
>>54921958
Oh, CRC, Cyclic Redundancy Check.
but why
Maybe it has to do with the source files - when you download the torrent, it already checks the hashes for you, because it has to verify it has the entire file.
>>54922107
torrent clients do that by way of the torrent file anyway
At a guess the CRC is more for applying patches (v2, v3, etc.), as they'll only work on the exact file they're made for, so including the CRC in filename is helpful in that case.
>>54922325
Don't forget about IRC, fansubbers tend to use it for distribution on top of torrents.
It's useful because we don't get as many leechers complaining that it's our fault their video doesn't play when they just got a broken/incomplete download. It's also pretty convenient to search by checksum on irc. It's not really necessary but it doesn't hurt to have so why not?
>>54921854
They are CRC32, specifically using the standard CRC32 polynomial: x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x^1+1.
The software used to generate them is sfv, or cksfv to verify.
They're not secure, but they are reasonable for checking that the file is intact: a reasonable concern for XDCC, which is absurdly simple.
Groups don't always get the filenames right.
