Security of cryptographic hash functions: Difference between revisions

Revision as of 18:01, 28 January 2011

Revision as of 10:10, 15 February 2011

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In other words, most of the hash functions in use nowadays, are not provably collision-resistant. These hashes are not based on purely mathematical functions. This approach results generally in more effective hashing functions, but with the risk that a weakness of such a function will be eventually used to find collisions. The famous case is [[MD5]].

Meaning of "hard to find collision" in these cases means "almost certainly beyond the reach of any adversary who must be prevented from breaking the system for as long as the security of the system is deemed important." The meaning of the term is therefore somewhat dependent on the application, since the effort that a malicious agent may put into the task is usually proportional to his expected gain. However, since the needed effort usually grows very quickly with the digest length, even a thousand-foldthousandfold advantage in processing power can be neutralized by adding a few dozen bits to the latter.

== Provably Secure Hash Functions ==