On Mon, Dec 9, 2024 at 9:28 AM Peter Dimov
"seed" "message" and "seedm" "essage" trivially collide, which may not be desirable.
Sorry, I don't follow. You are comparing the result of two different hash functions: H1 h1( "seed", 4 ); h1.update( "message", 7 ); auto r1 = h1.result(); H2 h2( "seedm", 5 ); h2.update( "essage", 6 ); auto r2 = h2.result(); assert( r1 == r2 ); h1 and h2 are different hash functions from the same family [1] and you have gone out of your way to form a preimage utilizing knowledge of the seed. Hardly fair and also does not in any way reflect the security concerns of real use-cases. Your own implementation of the seeded FNV-1a constructor simply calls update(): https://github.com/pdimov/hash2/blob/7a25f8518692b657e9272884519519fbaca2ec5... I think it would be preferable if Hash2 made this the default implementation, and allowed more sophisticated algorithms (and authors) to opt-in to a better implementation. Otherwise, we are forcing ordinary users who just want to adapt an external library to meet the HashAlgorithm requirements to become experts. [1] https://en.wikipedia.org/wiki/Universal_hashing [2] https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function