Is SipHash cryptographically secure? I'm evaluating different hash algorithms for use in my application. One of the kind of algorithms I am looking at are cryptographically secure ones to protect against DOS attacks. 

SipHash seems pretty great, but the creators seem very careful to not call it "cryptographically secure". 

In the SipHash paper (PDF), they call it “cryptographically strong”, but not secure. Is there any reason to trust SipHash over SpookyHash if both have no known DOS attacks and neither is “cryptographically secure”?
A fast 64-bit hash cannot be completely secure, since a $2^{32}$ brute force collision search is completely doable, and even a $2^{64}$ preimage attack could be feasible.

As a MAC used for hash table keying, that doesn't really matter (unless you leak the key). Finding just a few collisions isn't a problem and gathering statistics for an attack would probably already constitute a DOS attack.

That is to say, SipHash isn't a secure hash function, but should be a strong PRF and thus a secure MAC.