Comment on SHA-3 to Be AnnouncedparentComments−kbolino13yIs there something about HMAC, which can augment any hash function, that makes it insufficient for the task?−tptacek13yYes. 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.−moonboots13yA 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.
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Is there something about HMAC, which can augment any hash function, that makes it insufficient for the task?
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.
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.