U Havent Reinstalled Recently Chances Are Youre Using Md5-based Passwords However The Password Hashes You Find In Etc Shadow - Converter Hash Generator, Message Digest Tool , Encryption , Decryption What is md4 hash? 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 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.