A CryptographicHash is a Hash for which is it is practically impossible to construct a document that results in a hash value known beforehand. This makes such hash functions useful for signing documents to assure their integrity. Several well known and understood algorithms fall in this category:

• MD2 as per RFC:1319, a good (still?) but slow hashing algorithm
• MD4 as per RFC:1320
• MD5 as per RFC:1321, based on MD2 but faster. People should be phasing out their use of this by now.
• SHA1 is newer and has fewer theoretical attack vectors than MD5, but is also showing signs of weakness.

A competition is currently in progress to come up with a new, stronger hash function to replace the above.

See also: CRC

CategoryCryptography