Re: [hash2] Question about cryptographic guarantees of hash_append_unordered_range

From: Kostas Savvidis (kotika98_at_[hidden])
Date: 2024-12-10 07:29:42

> On 8 Dec 2024, at 23:19, Peter Dimov via Boost <boost_at_[hidden]> wrote:
> Vinnie Falco wrote:
>> On Sun, Dec 8, 2024 at 11:27 AM Ivan Matek via Boost
>> <boost_at_[hidden]>
>> wrote:
>>> ...sum is commutative.
>> Bitwise XOR and modular unsigned multiplication are also commutative.
> 
> Bitwise xor has the problem that xoring two equal values yields 0, so
> the sequences [1], [1, 1, 1], [1, 2, 2] and so on all hash to the same thing.

And addition gives the same result for [3] , [2,1], [1,1,1] etc.

My guess is that a hash of an unordered set is probably impossible to make crypto-safe.
But maybe with modular exponentiation?

Cheers,
Kostas