I disagree with two big points in this talk, but I'm sorry to say they're the same two things I disagreed with last time, so this is going to be a boring comment.

First, dedicated AEAD cipher modes are superior to manually composing AES-CTR and HMAC-SHAx. AEAD modes provide both authentication and encryption in a single construction. AES-CTR+HMAC-SHAx involves joining two constructions to do the same thing.

Colin points to AES-GCM, the most popular AEAD mode, as an example of how AEAD modes can be more susceptible to side-channel attacks than AES-CTR+HMAC-SHAx. I don't think this is a strong argument for a couple reasons:

* AES-GCM is so far as I can tell no practical cryptographer's preferred AEAD mode; "whipping boy" might be a better role to ascribe to it.

* AES-GCM's side-channel issues are due principally to a hardware support concern (GMAC, AES-GCM's answer to HMAC, requires modular binary polynomial multiplication, which in pure software is table-driven, which creates a cache timing channel). That hardware support concern might be receding, and platforms that don't have AES-GCM might prefer a different AEAD mode anyways.

* Modern AEAD modes, of the sort being entered into CAESAR, have resilience against side channels as a design goal.

* But the most important rejoinder to Colin's preference for HMAC-SHAx over AEAD modes is this: HMAC-SHAx is responsible for more side-channel flaws than any other construction. Practically every piece of software that has implemented HMAC-SHAx has managed to introduce the obvious timing channel in comparing the candidate to the true MAC for a message. What's worse is, using AES-CTR+HMAC-SHAx in practice means that the developer has to code the HMAC validation themselves; it's practically an engraved invitation to introduce a new timing leak. Almost nobody codes their own AES-GCM.

I also think Colin is wrong about ECC, particular versus RSA.

RSA might be the most error prone cryptographic primitive available to developers. There are two big reasons for this:

* RSA has fussy padding requirements. The current best practices for RSA encryption and signing are OAEP and PSS (huge credit to Colin for getting this right in 2010). If you want to form an opinion about RSA, go read up on OAEP and ask yourself (honestly) if you would come up with anything resembling OAEP if you were called on to encrypt with RSA. Developers as a rule do not use OAEP; instead, most new software still uses PKCS1v15 padding, which introduces susceptibility to terrible vulnerabilities that can often be easily exploited in the wild. Even better are the Javascript developers who build RSA from first principles and skip the padding altogether (the fact that RSA padding is a requirement and not an annoyance to be avoided is why Nate Lawson says we should call it "RSA armoring" and not "RSA padding").

* RSA easily supports a direct encryption transform, which is widely used in practice. ECC software as a general rule does not synthesize an encryption transform from the ECDLP; instead, ECC software uses the ECDLP to derive a key, and then uses something like AES to actually encrypt data. You might be thinking, "that's how RSA software works too". But RSA in practice is subtly different: you can, for instance, easily encrypt a credit card number directly using RSA, or build a crappy key exchange protocol where the client encrypts (doesn't derive or sign, but encrypts) a key for the server. RSA and conventional DLP crypto therefore offer (encrypt, key-exchange, sign); ECC in practice offers just (key-exchange, sign). That's one less dimension of things developers have to get right in ECC cryptosystems.

Colin is smarter than me and much better trained in cryptography than I am. All I do is find and exploit crypto bugs in real software. I am usually as nervous as any of you are to challenge Colin about crypto, but I think I can win these two arguments. (Spoiler alert: Colin doesn't think so).