Md5
From Hackepedia
MD5 is a cryptographic one-way hashing algorithm first described in RFC 1321 back in 1992.
MD5 is no longer recommended for use, following a presentation at the 2004 Crypto Conference that revealed hash collision problems with the algorithm.
This MD5 sum is infamous:
d41d8cd98f00b204e9800998ecf8427e
What is it? An empty file.