Cryptographic hash function: Difference between revisions
Content added Content deleted
m (This is an encyclopædic entry, not a task) |
(recommend stronger alternative, etc.) |
||
| Line 1: | Line 1: | ||
[[Category:Encyclopedia]] |
[[Category:Encyclopedia]] |
||
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><ref> |
||
[https://en.wikibooks.org/wiki/Cryptography/Hashes Wikibooks: Cryptography: Hashes] |
|||
</ref> |
|||
* ''Preimage resistance.'' It is too difficult to invert the function and find an original message from its digest. |
* ''Preimage resistance.'' It is too difficult to invert the function and find an original message from its digest. |
||
| Line 11: | Line 13: | ||
== Algorithms == |
== Algorithms == |
||
[[SHA-256]] is the recommended stronger alternative to [[SHA-1]] and [[RIPEMD-160]], which in turn are stronger than [[MD5]], which in turn is stronger than [[MD4]]. |
|||
[[MD4]], [[MD5]], [[RIPEMD-160]], [[SHA-1]] |
|||
== References == |
== References == |
||
Latest revision as of 14:20, 22 January 2017
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][2]
- 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
SHA-256 is the recommended stronger alternative to SHA-1 and RIPEMD-160, which in turn are stronger than MD5, which in turn is stronger than MD4.
References
- ↑ Dobbertin, Bosselaers, Preneel. "RIPEMD-160, a strengthened version of RIPEMD"
- ↑ Wikibooks: Cryptography: Hashes