Message-Digest Algorithm (MD4)

MD4 is a cryptographic hash function and digest length 128 bits.

The MD4 Message-Digest Algorithm is a cryptographic hash function developed by Ronald Rivest in 1990.The digest length is 128 bits. The algorithm has influenced later designs, such as the MD5, SHA-1 and RIPEMD algorithms. The initialism "MD" stands for "Message Digest."

The security of MD4 has been severely compromised. The first full collision attack against MD4 was published in 1995 and several newer attacks have been published since then. As of 2007, an attack can generate collisions in less than 2 MD4 hash operations.

A theoretical preimage attack also exists.

Weaknesses in MD4 were demonstrated by den Boer and Bosselaers in a paper published in 1991.

The first full-round MD4 collision attack was found by Hans Dobbertin in 1995, which took only seconds to carry out at that time.

In August 2004, Wang et al. found a very efficient collision attack, alongside attacks on later hash function designs in the MD4/MD5/SHA-1/RIPEMD family. This result was improved later by Sasaki et al., and generating a collision is now as cheap as verifying it (a few microseconds).