12 Dec
2024
12 Dec
'24
3:50 p.m.
Andrey Semashev wrote:
On 12/12/24 16:22, Peter Dimov via Boost wrote:
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.
But the original hash algorithm h does depend on the seed, and so does its final result.
void hash_append_unordered_range( Hash& h, Flavor const& f, It first, It last ) std::uint64_t w = 0; // compute w from [first, last) hash2::hash_append( h, f, w ); hash2::hash_append_size( h, f, m ); If two different ranges produce the same w, the final result will be the same, even though it does depend on the seed.