Talk:UOWHF

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[edit] Confusing and contradicting

This article needs to be improved. Here are just a few places where the current article is confusing and contradicting:

That's already wrong. One of the advantages of UOWHF is that they have weaker assumptions than cryptographic hash functions, hence UOWHF need not necessarily be cryptographic hash functions.

  • Collision Resistant Hash Functions (CRHF) are based on the stronger assumption that finding a collision in hash function is impossible.

Again, wrong. If the hash function is secure then it is only infeasible to find collisions not impossible.

Less secure than what?

  • UOWHFs are based on weaker assumption that finding a collision in t time units with probability ε is impossible, known as (t,ε)-UOWHF's.

This seems to describe a cryptographic hash function. If I understand it correctly, then UOWHFs require some form of 2nd preimage resistance and not collision resistance.

  • And collision resistance is achieved by applying hash functions several time from this family.

I can't find such a theorem in the papers given as reference.

  • These functions need keys to operate on them.

Again, I can't find any reference for using keys in the definition given by Naor and Yung.

  • In CRHF the adversary wins the game once he finds a collision pair.

Taken out of context.

  • Assuming CRHF and designing hash functions based on that would be a costly mistake.

Confusing. Why would it be a mistake to design a collision resistant CRHF?

  • The security bound is 2n when the output length is n.

This is unclear, because it is taken out of context.

  • In UOWHF the adversary does not win for any collision. He has to specify a state, say S, and then he gets the key K. He now has to find a collision for the specified S and hK.

Again, unclear because the role of the keys has not been specified.

  • To achieve higher order UOWHF at the same time.

Undefined. What are higher order UOWHFs?

Unclear. Does that mean if UOWHFs exist then a secure signature scheme exists or does it mean that some signature schemes in use today are based on UOWHFs? 85.2.41.214 13:06, 9 July 2007 (UTC)