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No, it's not a cryptographic hash function. It's a MAC function.

The paper clearly states that it is not collision resistant.

I believe that you and tptacek may be using differing definitions of "cryptographic", because he tends to knows what he's talking about when it comes to cryptography (e.g. https://gist.github.com/tqbf/be58d2d39690c3b366ad).

Oh, well.

What I think of as "cryptographic hash function" is a function resistent to pre-image attack, second pre-image attack, and collision generation.

Neither of those are satisfied by SipHash, and can thus not classify as a cryptographic hash function by the normal definition.

It's a cryptographic hash function, but not one suitable for all of the same applications as SHA2. It has security characteristics that other hash-table hashes (for instance) lack.

If you know the key, it is as weak as it gets (as the paper notes too, you can construct collisions easily if the key is known), so I disagree.

Honestly, I really don't care about this debate, except to the extent that it's about whether SipHash "isn't cryptographic and therefore you might as well use CityHash or SeaHash", which just isn't true.

I agree. SipHash is certainly strong if you don't know the key.

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