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'''CRC-verified | {{TOCright}} | ||
*A '''CRC-verified file''' is a file for which the CRC has been found to be the same as a released 'good CRC'; it is very likely that the file is a good copy. | |||
*A '''CRC-failed file''' is a file for which the CRC has been found to be ''different'' from a released 'good CRC'; ''it is very likely that the file is corrupt in some way''. | |||
If you've hashed a file for use it with [[ed2kdump]], and AniDB lists it as 'CRC-verified', you don't need to do any further verification: the file is definitely uncorrupted. | |||
==About CRC== | |||
A CRC is a form of file hash: a short representation of a longer file that is likely to change if the file is modified. CRC is a 32-bit hash, which means that the chances of a random corruption not changing the CRC are four million to one against. Many groups release CRC hashes of their released files, so you can make sure you've downloaded them correctly. | |||
Any change, from a single changed bit to widespread changes throughout the file, will change the CRC. While a single-bit error is often imperceptible, files with major corruption may be unplayable. It is possible to patch a corrupt file to a known-good version using a tool such as [[Zidrav]] or [[QuickPar]]. | |||
The other hashes AniDB lists (MD5, SHA-1, and ed2k) are ''stronger'' than CRC: the chance of a CRC differing between two files with the same ed2k, SHA-1 or MD5 hash is at least 79 billion billion billion to one. If the MD5, SHA-1, or ed2k hash matches a published 'good hash', then it is very unlikely indeed that the CRC will fail. When AniDB lists a file as CRC-verified, you can use any of the hashes listed to verify the file. | |||
==External links== | |||
*[[Wikipedia:Cyclic redundancy check|CRC article on Wikipedia]] | |||
[[Category:Definitions]] | [[Category:Definitions]] |
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