MD5
MediaWiki uses MD5 hashes in a few places to break up large directories into subdirectories based on the MD5 hashes of titles.
MD5 is no longer considered as a secure hash for encrypting password (SHA1 or better is recommended for such usage, where MD5 is strongly discouraged in favor of SHA1).
But MD5 remains a wellknown good hashing function for splitting long lists into sublists (even though SHA1 would be equally fast and would offer a slightly better statistic distribution).
See also
- MediaWiki file usage in the MediaWiki documentation.
- for general information about the algorithm.