Saturday, June 8, 2013

Traffic Analysis

I once worked for NSA. At that time it was unlawful for me to say what NSA did, except to say that we made codes to prevent other countries from reading our communications. The rest of what NSA did was an pretty-easily-guessed secret. My job title was cryptologic mathematician.

During WW2, if Hitler turned on a radio, and sent a message to Rommel, it might be that the predecessor of the UK's GCHQ had an antenna and a receiver that picked up the transmission. The Brits had a lot of people employed at places like Bletchley Park. And a lot of other places to do science on that sort of thing.

Imagine you have an enemy who uses the radio and you have smart guys who want to wring as much information out of the enemy's communications as possible. The really juicy stuff is encrypted, so you don't know what exactly they're saying. But you do know that Hitler talks to Rommel, and Rommel talks to Fritz and Fritz talks to Brunhilde. Studying these patterns is called traffic analysis. It's the best you can do if you can't get hold of the internals of messages.

By doing traffic analysis, we may not know what is said, but we know who is talking and when. For instance, suppose you want the Nazis to think George Patton is going to cross the English Channel at Calais. You might put up a bunch of inflatable tanks and planes on the coast, but the Nazis won't fall for it unless you've actually got "ole blood 'n' guts" talking on the radio and lots of radio replies between those rubber tanks and planes. This was one of the reasons why Hitler could not believe that D-Day was going to be at Normandy. His technical boffins told him where Patton was and how much Army he had around him.

The US is smarter than that. We get eye-witness accounts of one of the 9-11 terrorists being in Prague and the 9-11 Commission denies them because we know his cell phone (that won't work in Europe) is in the US. Nobody would ever think to lend his cell phone to a friend while he's travelling.

I figure all of the Al Qaeda operatives are dead who haven't already figured out how traffic analysis works. There's a sort of Darwinian selection process that winnows out those terrorists who don't luck into effective NSA-evading strategies.

Here's another application of traffic analysis that you might be a little familiar with. Your wife asks you some difficult, pointed questions about an unfamiliar number that keeps showing up on your cell phone bills. 

Maybe you escape those difficult questions because the phone number doesn't show the name "Bubbles Mattressthrasher." Your adulterous communications are a little bit easier to hide because your wife can only see one piece of the puzzle. She can't see Bubbles' cell phone bill, and infer from her communications with furriers and jewelers that certain charges on your credit card can be explained thereby.

If you have the morality of a politician, you're grateful spouses can't do the deeper kind of traffic analysis data I just outlined.

One of the reasons why the US came into WW2 and threw so much effort into the European Theater (as opposed to the Pacific Theater where we'd been attacked), was the collapse of Isolationist opposition. And one of the reasons for that was the active intelligence operation conducted against US politicians by the Brits who actively set up Isolationist politicians with honey traps to blackmail them into voting favorably to the UK. Arthur Vandenberg was a Michigan Senator from my home town of Grand Rapids who mysteriously voted FOR the lend-lease bill despite his Isolationist politics.

But that's OK because they were fighting Hitler. And they were foreigners, no US bureaucrat would do anything like that.

Of course, J. Edgar Hoover managed to stay in charge of the FBI for all of his adult life despite serving Presidents all over the political spectrum who hated him. And despite concerted efforts to depose him, or retire him, he always managed to hang on. It was almost like he had some magic that he could use against his enemies.

Since 9/11 a lot of blood and treasure has gone into creating a comprehensive surveillance regime of digital communications passing through the US. It seems that our wise and benevolent leaders have access to AT THE VERY LEAST all the cell phone bills in this country. 

Despite all of this a couple foreigners managed to plot and perpetrate a bombing attack on the Boston Marathon. So, why did we spend all that money?

If it doesn't catch terrorists, what does it catch?

Put on your tin foil hat before I ask the next question: 

Have you ever noticed how politicians change after they go to Washington? I'm sure there are lots of reasons: getting the money from lobbyists for reelection campaigns comes to mind. Or playing to a National stage.

But if I were a politician with any damaging secrets that could be penetrated by traffic analysis, I'd assume they're known to persons within the NSA. 

And we can trust them like we trust the IRS with our financial data.


  1. Wow, that's quite a mouthful and a lot to think about. You sure do have great writing skills :)

    1. Thanks Doug. i'll buy you lunch if you keep talking like that.


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