The first two references you cite are attacks against a password hash. Blake3 is not a password hash, it is a general-purpose hash.
The third reference is not an attack on the hash function timing, it is an attack against hash table timing, which is not at all the same thing. From the abstract:
"Our attack does not rely on any weakness of a particular hash function and can work against any hash."
Once again: Blake3 is a general-purpose hash, not a password hash. General-purpose hashes cannot be constant-time because they must operate on inputs of arbitrary length.
Then I think you misunderstood rurban's post. He's saying it is a property cryptographic hash functions must have that they are constant time, constant power. Yes, all cryptographic hashes suitable for general-purpose use have this property. That's part of why they are good general-purpose hash functions.
And each round of Blake3 is constant-time, irrespective of input. We're talking about rounds (or, alternatively, constant-time for equivalent length input).
> He's saying it is a property cryptographic hash functions must have that they are constant time, constant power.
It's a little unclear whether rurban was saying that they must have this property, or merely that they do have it. But that is neither here nor there because...
> each round of Blake3 is constant-time
That is not the same thing as the entire algorithm being constant-time.
This whole thread has turned into a horrible mess.
Yes, all else being equal, constant time/power is nice to have. But the only circumstance under which it is necessary is if you are processing secret data in a situation where an adversary can potentially observe side channels. But this is true for any algorithm, not just hashes. Furthermore, most common application of hashing a secret is password hashing, and there is is much more important that the hash be expensive than that it be constant time and power.
But Blake3 is not a password hash. It can be used as a component of a password hash, and there its constant-round time becomes a useful property. But to emphasize this in the context in which rurban's comment appears is at best badly misleading.
