[Cryptography] Suite B after today's news

Jon Callas jon at callas.org
Thu Sep 5 22:00:21 EDT 2013

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On Sep 5, 2013, at 6:16 PM, Dan McDonald <danmcd at kebe.com> wrote:

> Consider the Suite B set of algorithms:
> 	IEEE Elliptic Curves (256, 384, and 521-bit)
> Traditionally, people were pretty confident in these.  How are people's confidence in them now?

My opinion about GCM and GMAC has not changed. I've never been a fan.

My objection to them is that they are tetchy to use -- hard to get right, easy to get wrong. It's pretty much what is in Niels's paper:


I don't think they're actively bad, though. For the purpose they were created for -- parallelizable authenticated encryption -- it serves its purpose. You can have a decent implementor implement them right in hardware and walk away.

I think that any of OCB, CCM, or EAX are preferable from a security standpoint, but none of them parallelize as well. If you want to do a lot of encrypted and authenticated high-speed link encryption, well, there is likely no other answer. It's GCM or nothing.

Remember that every intelligence agency has a SIGINT branch and an IA (Information Assurance) branch. Sometimes they are different agencies (at least titularly) like GCHQ/CESG, BND/BSI, etc. The NSA does not separate its SIGINT directorate and the IA directorate into different agencies.

I think the IA people have shown they do a good job, but they are humans too and make mistakes. Heck, there are things that various IA people do and recommend that I disagree with from weakly to strongly. I weakly disagree with GCM -- I think it's spinach and I say to hell with it, as opposed to thinking it's crap.

Would a signals intelligence organization that finds a flaw in what the IA people did tell the IA branch so people can fix it? That's the *real* question.


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