Cryptographic hash function: Difference between revisions
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A [[wp:cryptographic hash function|cryptographic hash function]], also known as a ''collision resistant hash function'', maps a message (of any length) to a digest (of a fixed length), and has the following three properties:<ref>Dobbertin, Bosselaers, Preneel. [http://homes.esat.kuleuven.be/~bosselae/ripemd160.html "RIPEMD-160, a strengthened version of RIPEMD"]</ref> |
A [[wp:cryptographic hash function|cryptographic hash function]], also known as a ''collision resistant hash function'', maps a message (of any length) to a digest (of a fixed length), and has the following three properties:<ref>Dobbertin, Bosselaers, Preneel. [http://homes.esat.kuleuven.be/~bosselae/ripemd160.html "RIPEMD-160, a strengthened version of RIPEMD"]</ref> |
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Revision as of 09:38, 2 April 2012
A cryptographic hash function, also known as a collision resistant hash function, maps a message (of any length) to a digest (of a fixed length), and has the following three properties:[1]
- Preimage resistance. It is too difficult to invert the function and find an original message from its digest.
- Second preimage resistance. It is too difficult to change the message without also changing its digest.
- Collision resistance. It is too difficult to find any two messages with the same digest.
With many algorithms, the message is a string of octets, and the digest has a fixed number of bits. For example, SHA-256 always computes a 256-bit digest. One can write this digest in hexadecimal.
Though algorithms like MD4 define digest for message of any bit length, many actual implementations assume that the bit length is a multiple of 8.
Algorithms
MD4, MD5, RIPEMD-160, SHA-1
References
- ↑ Dobbertin, Bosselaers, Preneel. "RIPEMD-160, a strengthened version of RIPEMD"