Crypto Is Not A Panacea

Bricks

I was going to write this to an internal mailing list, following this week’s PRISM excitement, but I’ve decided to put it here instead. It was written (and cribbed from other stuff I’ve written elsewhere) in response to an argument that encrypting everything would somehow solve a scary-sounding though imprecisely-specified problem, a claim you may not be surprised to find out I think is foolish.

I’ve written about this elsewhere, so forgive me, but: I think that it’s a profound mistake to assume that crypto is a panacea here.

Backstory time: in 1993, the NSA released SHA, the Secure Hashing Algorithm; you’ve heard of it, I’m sure. Very soon afterwards – months, I think? – they came back and said no, stop, don’t use that. Use SHA-1 instead, here you go.

No explanation, nothing. But nobody else could even begin to make a case either way, so SHA-1 it is.

It’s 2005 before somebody manages to generate one, just one, collision in what’s now called SHA-0, and they do that by taking a theoretical attack that gets you close to a collision, generalizing it and running it for around 80,000 CPU hours or so on a machine with 256 Itanium-2 processors running this one job flat out for two weeks.

That hardware straight up didn’t exist in 1993. That was the year the original Doom came out, for what it’s worth, so it’s very likely that the “significant weakness” they found was found by a person or team of people scribbling on a whiteboard. And, note, they found the weaknesses in that algorithm in the weeks after publication when those holes – or indeed “any holes at all” – would take the public-facing crypto community more than a decade to discover were a theoretical possibility.

Now, wash that tender morsel down with this quote from an article in Wired quoting James Bamford, longtime writer about all things NSA:

“According to another top official also involved with the program, the NSA made an enormous breakthrough several years ago in its ability to cryptanalyze, or break, unfathomably complex encryption systems employed by not only governments around the world but also many average computer users in the US. The upshot, according to this official: “Everybody’s a target; everybody with communication is a target.”

“Many average computer users in the US”? Welp. That’s SSL, then.

So odds are good that what we here in the public and private sectors consider to be strong crypto isn’t much more of an impediment for the NSA than ROT-13. In the public sector AES-128 is considered sufficient for information up to level “secret” only; AES-256 is for “top secret”, and both are part of the NSA’s Suite B series of cryptographic algorithms, outlined here.

Suite A is unlikely to ever see the light of day, not even so much as their names. The important thing that this suggests is that the NSA may internally have a class break for their recommended Series B crypto algorithms, or at least an attack that makes decryption computationally feasible for a small set of people that includes themselves, and indeed for anything weaker, or with known design flaws.

The problem that needs to be addressed here is a policy problem, not a technical one. And that’s actually great news, because if you’re getting into a pure-math-and-computational-power arms race with the NSA, you’re gonna have a bad time.

One Comment

  1. Mike Kozlowski
    Posted June 8, 2013 at 10:16 am | Permalink

    FWIW, Bruce Schneier doesn’t think they can break AES: http://www.schneier.com/blog/archives/2012/03/can_the_nsa_bre.html