Message Digest 5

What Does Message Digest 5 Mean?

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.

Techopedia Explains Message Digest 5

Details of the Message Digest 5 algorithm are provided in RFC 1321. The algorithm of Message Digest 5 makes use of a message of any length and outputs a 128-bit message digest of the input. The Message Digest 5 algorithm does not need any large substitution tables and is an extension of the Message Digest 4 algorithm. Compared to Message Digest 4, Message Digest 5 is more conservative in design but is slower. The steps involved in the Message Digest 5 algorithm are appending of padding bits, appending representation of padded message to the original message, initialization of message digest buffer, processing of message in 16-word blocks and finally outputting the result. Compared to Message Digest 4, Message Digest 5 is slightly more complex.

On a 32-bit machine, Message Digest 5 performs much faster compared to other message digest algorithms. Message Digest 5 is simple to implement when compared with similar digest algorithms. The difficulty of coming up with same message digest from two different messages are on the order of 264 operations.


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Margaret Rouse

Margaret Rouse is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical, business audience. Over the past twenty years her explanations have appeared on TechTarget websites and she's been cited as an authority in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine and Discovery Magazine.Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages. If you have a suggestion for a new definition or how to improve a technical explanation, please email Margaret or contact her…