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irrc a cryptosecure hash is computationally infeasible to generate a new sample that has the same hash. that is if you know hash (or reasonably small, ie only

irrc a cryptosecure hash is computationally infeasible to generate a new sample that has the same hash. that is if you know hash (or reasonably small, ie only a percent of the total bit space), it's improbable bordering on impossible to generate a false positive .

__blockcipher__ 5y ago
Agreed. From my comment: > although (to your point) without doing any magic to intentionally cause a collision, effectively you will never get one because of just how many damn buckets there are
gpm 5y ago
Repeating that this process doesn't appear to be using cryptographic hash functions in the first place, so this conversation isn't relevant, but: Only in the sense that "we don't know of a way to generate a new sample that has the same hash, yet". Unless we can prove P!=NP, we can't even prove that there exist hash functions that are actually infeasible to generate a sample with the same hash - so far we are no where close to knowing whether P!=NP or P=NP. Even if we assume P!=NP, that doesn't mean that it is infeasible to generate collisions for our current cryptographic hash functions. They're not backed by some mathematical proof of correctness assuming <assumptions>, just the fact that so far no one has publicly figured out a way to break them, and the people who spend time trying think that their design is one that is unlikely to be broken in the near future. We have managed to find collisions against hash functions that we previously considered cryptographically secure, that were designed with the same sort of standard in mind: E.g. md5 (https://en.wikipedia.org/wiki/MD5#Collision_vulnerabilities https://en.wikipedia.org/wiki/MD5#Collision_vulnerabilities) and sha1 (https://en.wikipedia.org/wiki/SHA-1#Birthday-Near-Collision_Attack_%E2%80%93_first_practical_chosen-prefix_attack https://en.wikipedia.org/wiki/SHA-1#Birthday-Near-Collision_...). There's no great reason to think that private groups could not have an attack against current hash functions [1], and there's definitely no reason to think that they won't find one in the future. [1] There sort of is for SHA2, and that's that bitcoin has effectively created a giant bounty for breaking it.

__blockcipher__ 5y ago

Agreed. From my comment: > although (to your point) without doing any magic to intentionally cause a collision, effectively you will never get one because of just how many damn buckets there are

gpm 5y ago

Repeating that this process doesn't appear to be using cryptographic hash functions in the first place, so this conversation isn't relevant, but: Only in the sense that "we don't know of a way to generate a new sample that has the same hash, yet". Unless we can prove P!=NP, we can't even prove that there exist hash functions that are actually infeasible to generate a sample with the same hash - so far we are no where close to knowing whether P!=NP or P=NP. Even if we assume P!=NP, that doesn't mean that it is infeasible to generate collisions for our current cryptographic hash functions. They're not backed by some mathematical proof of correctness assuming <assumptions>, just the fact that so far no one has publicly figured out a way to break them, and the people who spend time trying think that their design is one that is unlikely to be broken in the near future. We have managed to find collisions against hash functions that we previously considered cryptographically secure, that were designed with the same sort of standard in mind: E.g. md5 (https://en.wikipedia.org/wiki/MD5#Collision_vulnerabilities https://en.wikipedia.org/wiki/MD5#Collision_vulnerabilities) and sha1 (https://en.wikipedia.org/wiki/SHA-1#Birthday-Near-Collision_Attack_%E2%80%93_first_practical_chosen-prefix_attack https://en.wikipedia.org/wiki/SHA-1#Birthday-Near-Collision_...). There's no great reason to think that private groups could not have an attack against current hash functions [1], and there's definitely no reason to think that they won't find one in the future. [1] There sort of is for SHA2, and that's that bitcoin has effectively created a giant bounty for breaking it.