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More puzzles from the Puzzle Palace

A reader pointed me to an apparently dull collection of NSA documents recently posted by that useful source, One of the hidden gems is a "CMI Newsletter" containing a eight pages of crypto puzzles.

I've taken the liberty of posting the CMI Newsletter separately (PDF, click this link), but kudos go to GovernmentAttic for dredging up this diamond in the rough. If you work out answers, feel free to post them here, or at least provide a pingback so interested people can find them.

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Boak's Puzzle Revisited

A reader, GregoryF, has proposed a solution to Boak's puzzle. Many years ago, David G. Boak of the NSA gave lectures to train employees on communications security matters. In one case he presented a written story about insufficiently burned crypto materials (keys, etc.), several tons' worth, that needed disposal.

Boak didn't quite explain how they disposed of the waste. Instead, he coded the answer using an innocent text system and challenged the readers to solve it.

GregoryF's solution is posted as a comment to the earlier article. He actually came up with two different solutions. The "system" behind the second solution gets somewhat complicated, which casts some doubt on its correctness. Also, I haven't quite recovered the same results.

Spoilers ahead!

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Boak's Puzzle: Disposing of Classified Trash

Recently I was skimming through the NSA's "classified history of COMSEC" (posted at  This "history" is a transcription of lectures by David G. Boak, who liked to explain NSA-related topics from a historical perspective. He clearly inspired a generation of NSA's employees. The last "real" page of the document contains a humorous story and a crypto puzzle (link to pdf).

The NSA had an incinerator in their old Arlington Hall facility that was designed to reduce top secret crypto materials and such to ash. Someone discovered that it wasn't in fact working. Contract disposal trucks had been disposing of this not-quite-sanitized rubish, and officers tracked down a huge pile in a field in Ft. Meyer.

How did they dispose of it? The answer is encrypted in the story's text!

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