On: SHA-3 to Be Announced

[kbolino]

Is there something about HMAC, which can augment any hash function, that makes it insufficient for the task?

[tptacek → kbolino]

Yes. HMAC is very slow. Also, length extension is a pernicious and scary little property to have lurking around your crypto designs; you want it gone.

[moonboots → kbolino]

A hash function immune to length extension attacks is more fool-proof than HMAC because there is no additional construct required. It's also faster because it requires no additional passes over data.