Message Digest 5 (MD5) is a hash function used in cryptography. Developed by Ronald Rivest in 1991, Message Digest 5 produces a 128-bit resulting hash value. Similar to other message-digest algorithms, it was largely developed for digital signature applications which make use of a large compressed file in a secure fashion.

Although it is still widely used, security of the function is severely compromised and as a result most applications, especially ones related to the U.S. government, require the SHA-2 family of hash functions for cryptography. Message Digest 5 is considered to be broken and unsuitable for further use according to the U.S. Department of Homeland Security.