Re:BitTorrent v2
by throwaway2048 on Monday September 07, 2020 @11:05PM
(#24404874)
you are massively prematurely optimizing, the vast majority of torrents are greater than a few hundred megabytes, nobody cares about the overhead of a few KB of hashes, you are already hashing data when you download or upload it, adding in another hash when data is fresh in the CPU cache is basically free.
No, "they" don't. SHA1 collisions had been "in the wind" for a while, they had been in sight ever since MD5 started showing signs of clear weakness in the early '00s. Wikipedia has a Rivest quote about it from 2005. There is nothing like that for SHA2, although attacks are improving.
> What are the chances of a collision if we simultaneously use multiple hashes
Define "simultaneous". Shipping twice the hashes for each piece seems a big waste of space. If you mean re-hashing hashes, it's just a waste of cpu power, since an attacker only has to break one or the other to get in a position to poison data.