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John Nash's Letter to the NSA (agtb.wordpress.com)
296 points by ckuehne on Feb 17, 2012 | hide | past | web | favorite | 28 comments

National Geographic recently had a "special" on "Inside the NSA: America's Cyber Secrets" where they mentioned and showed this letter. They said the NSA didn't end up doing anything with it but still wanted to classify it for 50+ years so that no one else could use the ideas within.

My favorite parts of the episode were:

- All of the Windows XP machines everyone was using

- The flashing red lights on the ceiling in secure areas (familiar for those that have been in similar secure facilities)

- The obnoxious re-enactments where real employees pretend to gather and discuss on-going developments. It was outright silly.

The episode just aired in January and it looks like it isn't on their site yet, but there are related videos: http://www.nationalgeographic.com/search/?search=%22Inside+t...

EDIT: The NSA press release mentions it too. They say "featured" but they didn't spend more than 5 minutes out of the hour program.

   The Nash letters were also recently featured on the National Geographic [...]

Why the lights on the ceiling?

In secure facilities (particularly defense related) where secret information or networks are in use, visitors must be accompanied by an escort and announced before entering. Everyone has to stop any actual sensitive work, shut off their monitors to sensitive systems, and cover up sensitive documents on your desk. Then as long as the visitor is in a certain area of the building, red flashing lights (no siren/noise) must stay on to alert everyone else that an un-cleared visitor is currently in the area. This is why most "actual work" gets done in basements and extra-secure rooms where visitors rarely ever see, because the constant interruptions are devastating.

To announce that there are uncleared visitors in the room, so don't discuss anything confidential.

I can't help but think that the NSA would have taken the letter more seriously if had been typed.


Type math? In 1955? That would have required specialized equipment, possibly a secretary. Nash clearly believed that the contents were of national security interest.

I thought the standard thing to do was type the text and then include the equations or diagrams as hand drawn figures in empty space on the page.

He should have invented TeX.

I think he did. Unfortunately he also invented fonts that appear to be hand-drawn by a person suffering from schizophrenia. =(

Here's a font that appears to be hand-drawn by a person suffering from megalomania: http://www.fonts101.com/fonts/view/Uncategorized/34398/Dijks...

I can't tell if you're kidding or not, but John Nash definitely did not invent TeX: http://en.wikipedia.org/wiki/TeX.

The diagram with the red and blue lines is particularly "interesting" for anyone not keeping up with the math.

"I'm not a crank. Here's a diagram of my machine." {Blue and red line everywhere}.

"I hope my handwriting, etc. do not give the impression I am just a crank or circle-squarer."

It seems he considered how a handwritten letter might be perceived.

Maybe the fact that it is not typed is a key to it's hidden meaning. Maybe there are reasons that only parts of this letter are clarified...

In all seriousness, this pdf basically unreadable. It would be nice if there was a readable version available to the general public. If there is one, please let me know because this is very interesting.

Basically unreadable? It's perfectly readable to me. Perhaps my own poor handwriting has given me better handwriting recognition.

The first time I looked at this pdf there were blocks of printed text all over the place that floated over the handwritten text. By floating over I mean literally covering the written text. After I read your comment I looked at it again and it was simply the handwritten text.

I'm not sure if my pdf reader confused things or the nsa has a special redirect for me. But the complete handwritten text is perfectly readable to me now. I'm not sure what I saw before, but it was odd...

I am pretty sure you can see them at the cryptography museum right next to the NSA. I went two weeks ago and Nash letter is right in the front.

I wonder what letters / blog posts / emails are written now that will make us look back in awe in 60 years.

I wonder if such things still happen. In 1955, the world was a lot less interconnected, and there was a much more real sense of global tension such that you would want to keep secrets. Today I'm not sure an academic would be so quick to dash off a letter to someone who would keep their discoveries secret for half a century.

Tough call---part of me says that they blew it off while the rest of me says they put the information to work (as best as they were able) In any event I doubt they got back to him...

Amusing anecdote, I was quite taken with the 'Java Ring' (which was a class ring type ring with a Dallas iButton on it) because it could be a 'secret decoder ring' with real crypto, except that all the crypto bits were disabled because they did not have permission from the NSA to turn them on.

So I wrote an Enigma Machine simulator for it [1] which used BASE64 to encrypt (or decrypt) messages. And in the process of doing research for that article I discovered the patent for the 'rotor' used in enigma [2] which was filed in Oct 10th, 1944 but didn't issue until Oct 12th, 1976! Talk about your submarine patent! But the other interesting thing about 1976 is that the DES encryption standard was announced in November of that year.

I don't doubt for a minute that Nash's work was influential on the thinking at least of the development of that standard.

[1] http://www.javaworld.com/javaworld/jw-08-1998/jw-08-indepth....

[2] http://www.google.com/patents/US3984922

Oooh, enigma, submarine patent, U-110 so funny! http://instantrimshot.com/

Well, they might have used the idea, but it's not really something easily tractable even for them.

I have to admit, I'm reading Rivest's source code and I don't completely grok the encryption scheme yet, but it seems to me that it works like this. Here's the problem: you've got this very pretty conjecture which says "give me just 26 cards, there are about 2^88 permutations of them, and choosing one at random produces a much larger set of possibilities than we could guess in the forseeable future with brute-force techniques." He then provide a cipher which takes a shuffled deck and 26 spots in memory, and uses the red half and the black half to provide a random pathway for the bits through this network, since at each step there is an incoming bit which tells which way you shuffle. (And I gather that also some of the cards may basically be flipped upside down when storing the key, which means "flip the bit as you transmit it.")

It's perfectly valid as an observation, and a nice conjecture, although I'm a little bit concerned in many ways about the design, since it still seems like it only has 2^26 state leaked pretty straightforwardly one bit at a time from two different locations. But maybe he's correct.

Still there's something technologically missing. This is a very simple algorithm for modern computers with their array lookups, and I suppose the military had all the budget they needed to build large machines which can actually push around these bits, but that sort of mixing network would have been really difficult to implement mechanically. In a world where computers were too expensive to distribute to every ship's captain, I could see the NSA being much less interested in this sort of physically pushing bits around a complicated network via pathways that won't be known until run-time.

From a cursory read of the PDF [1], it would seem that Mr. Nash was describing a stream cipher [2].

[1] http://courses.csail.mit.edu/6.857/2012/files/H03-Cryptosyst...

[2] http://en.wikipedia.org/wiki/Stream_cipher

The PDF record shows both parties replied to each other a couple times but the NSA thought his method didn't meet their security criteria.

But they also could have shelved it for years until someone had a use for it, the same as Hedy Lamarr's frequency hopping patent. (Granted, they probably modified it slightly so they didn't have to give him any credit)

This may be of some use to you: http://en.wikipedia.org/wiki/Hedy_Lamarr

It's "Hedley"!

(Sorry - mandatory "Blazing Saddles" joke.)

GCHQ didn't appear to make any use of Public Key crypto, even though Clifford Cocks created it.

But maybe there's a bunch of documents that are still secret.

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