Re: [boost] [hash2] Difference from paper: HashAlgorithm interface vs. function object

Joaquín M López Muñoz wrote:

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No dia 12 de dez. de 2024, às 14:22, Peter Dimov via Boost escreveu:

Using default-constructed instances of the hash algorithm, instead of copies, makes the hashing seed-independent, which means that a way to engineer collisions will work regardless of the seed used.

Can’t you construct h2 by seeding it with a result from h (possibly after updating h with the range size)?

That's (a) much slower and (b) requires the ability to obtain a result without perturbing the state, which is basically equivalent to making a copy.