Bug: 18088752 Change-Id: I027f9530a02cca081aae8eb94833d2fdcb678e9a
This also adds the MAC length constraint on imported HMAC keys. HMAC doesn't work without this constraint at the moment. Bug: 18088752 Change-Id: I8613f58f5d2a84df00bcf6179d13e30619440330