MySQL 5.5 Release Notes
The following software may be included in this product:
md5 (Message-Digest Algorithm 5) This code implements the MD5 message-digest algorithm. The algorithm is due to Ron Rivest. This code was written by Colin Plumb in 1993, no copyright is claimed. This code is in the public domain; do with it what you wish. Equivalent code is available from RSA Data Security, Inc. This code has been tested against that, and is equivalent, except that you don't need to include two pages of legalese with every copy. The code has been modified by Mikael Ronstroem to handle calculating a hash value of a key that is always a multiple of 4 bytes long. Word 0 of the calculated 4-word hash value is returned as the hash value.