MD5
| General | |
|---|---|
| Designers | Ronald Rivest |
| First published | April 1992 |
| Series | MD2, MD4, MD5, MD6 |
| Cipher detail | |
| Digest sizes | 128 bit |
| Block sizes | 512 bit |
| Structure | Merkle–Damgård construction |
| Rounds | 4 |
| Best public cryptanalysis | |
| A 2013 attack by Xie Tao, Fanbao Liu, and Dengguo Feng breaks MD5 collision resistance in 218 time. This attack runs in less than a second on a regular computer. | |
The MD5 algorithm is a widely used hash function producing a 128-bit hash value. Although MD5 was initially designed to be used as a cryptographic hash function, it has been found to suffer from extensive vulnerabilities. It can still be used as a checksum to verify data integrity, but only against unintentional corruption.
Like most hash functions, MD5 is neither encryption nor encoding. It can be reversed by brute-force attack and suffers from extensive vulnerabilities as detailed in the security section below.
MD5 was designed by Ronald Rivest in 1991 to replace an earlier hash function MD4. The source code in RFC 1321 contains a "by attribution" RSA license. The MD5 hash function receives its acronym MD from its structure using Merkle–Damgård construction.
The security of the MD5 has been severely compromised, with its weaknesses having been exploited in the field, most infamously by the Flame malware in 2012. The CMU Software Engineering Institute considers MD5 essentially "cryptographically broken and unsuitable for further use".
MD5 is one in a series of message digest algorithms designed by Professor Ronald Rivest of MIT (Rivest, 1992). When analytic work indicated that MD5's predecessor MD4 was likely to be insecure, Rivest designed MD5 in 1991 as a secure replacement. (Hans Dobbertin did indeed later find weaknesses in MD4.)
In 1993, Den Boer and Bosselaers gave an early, although limited, result of finding a "pseudo-collision" of the MD5 compression function; that is, two different initialization vectors that produce an identical digest.
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