http://md5.thaicpe.com/md5.phpIn cryptography, MD5 (Message-Digest algorithm 5) is a widely used, partially insecure[1] cryptographic hash function with a 128-bit hash value. As an Internet standard (RFC 1321), MD5 has been employed in a wide variety of security applications, and is also commonly used to check the integrity of files. An MD5 hash is typically expressed as a 32 digit hexadecimal number.
MD5 was designed by Ron Rivest in 1991 to replace an earlier hash function, MD4. In 1996, a flaw was found with the design of MD5. While it was not a clearly fatal weakness, cryptographers began recommending the use of other algorithms, such as SHA-1 (which has since been found vulnerable itself). In 2004, more serious flaws were discovered making further use of the algorithm for security purposes questionable.[2][3] In 2007 a group of researchers including Arjen Lenstra described how to create a pair of files that share the same MD5
http://en.wikipedia.org/wiki/MD5
