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Two Centuries On, a Cryptologist Cracks a Presidential Code
Posted: 03 July 2009 12:02 PM   [ Ignore ]
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For more than 200 years, buried deep within Thomas Jefferson’s correspondence and papers, there lay a mysterious cipher—a coded message that appears to have remained unsolved. Until now.

The cryptic message was sent to President Jefferson in December 1801 by his friend and frequent correspondent, Robert Patterson, a mathematics professor at the University of Pennsylvania. President Jefferson and Mr. Patterson were both officials at the American Philosophical Society—a group that promoted scholarly research in the sciences and humanities—and were enthusiasts of ciphers and other codes, regularly exchanging letters about them.

In this message, Mr. Patterson set out to show the president and primary author of the Declaration of Independence what he deemed to be a nearly flawless cipher. “The art of secret writing,” or writing in cipher, has “engaged the attention both of the states-man & philosopher for many ages,” Mr. Patterson wrote. But, he added, most ciphers fall “far short of perfection.”

To Mr. Patterson’s view, a perfect code had four properties: It should be adaptable to all languages; it should be simple to learn and memorize; it should be easy to write and to read; and most important of all, “it should be absolutely inscrutable to all unacquainted with the particular key or secret for decyphering.”

Mr. Patterson then included in the letter an example of a message in his cipher, one that would be so difficult to decode that it would “defy the united ingenuity of the whole human race,” he wrote.

There is no evidence that Jefferson, or anyone else for that matter, ever solved the code. But Jefferson did believe the cipher was so inscrutable that he considered having the State Department use it, and passed it on to the ambassador to France, Robert Livingston.

The cipher finally met its match in Lawren Smithline, a 36-year-old mathematician. Dr. Smithline has a Ph.D. in mathematics and now works professionally with cryptology, or code-breaking, at the Center for Communications Research in Princeton, N.J., a division of the Institute for Defense Analyses.

A couple of years ago, Dr. Smithline’s neighbor, who was working on a Jefferson project at Princeton University, told Dr. Smithline of Mr. Patterson’s mysterious cipher.

Dr. Smithline, intrigued, decided to take a look. “A problem like this cipher can keep me up at night,” he says. After unlocking its hidden message in 2007, Dr. Smithline articulated his puzzle-solving techniques in a recent paper in the magazine American Scientist and also in a profile in Harvard Magazine, his alma mater’s alumni journal.

The code, Mr. Patterson made clear in his letter, was not a simple substitution cipher. That’s when you replace one letter of the alphabet with another. The problem with substitution ciphers is that they can be cracked by using what’s termed frequency analysis, or studying the number of times that a particular letter occurs in a message. For instance, the letter “e” is the most common letter in English, so if a code is sufficiently long, whatever letter appears most often is likely a substitute for “e.”

Because frequency analysis was already well known in the 19th century, cryptographers of the time turned to other techniques. One was called the nomenclator: a catalog of numbers, each standing for a word, syllable, phrase or letter. Mr. Jefferson’s correspondence shows that he used several code books of nomenclators. An issue with these tools, according to Mr. Patterson’s criteria, is that a nomenclator is too tough to memorize.

Jefferson even wrote about his own ingenious code, a model of which is at his home, Monticello, in Charlottesville, Va. Called the wheel cipher, the device consisted of cylindrical pieces, threaded onto an iron spindle, with letters inscribed on the edge of each wheel in a random order. Users could scramble and unscramble words simply by turning the wheels.

But Mr. Patterson had a few more tricks up his sleeve…

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Posted: 03 July 2009 03:03 PM   [ Ignore ]   [ # 1 ]
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There is a difference between a code and a cipher, which apparently the author of that article doesn’t realise.  A cipher uses a specific formula to change the plain text into enciphered text.  For example, you might have the first letter of the alphabet is shown by the number one, the second letter of the alphabet shown by the number two, and so on.  So “Boo is a spork goddess of might” would then become “2-15-15 9-19 1 19-16-15-18-11 7-15-4-4-5-19-19 15-6 13-9-7-8-20”.  Ciphers are useful in that all you need to do is to remember the formula, and then you can encipher or decipher messages.  The weakness of ciphers is that somebody else can work out what the formula is, and then all of your messages could be easily read by them.

Codes, on the other hand, assign totally random symbols to represent words or letters.  You might have a code like this:

Boo = turnip
Is = Boris Yeltsin
A = frog
Spork = juggling
Goddess = doormat
Of = termite
Might = lizard

There’s no way to look at “Turnip Boris Yeltsin frog juggling doormat termite lizard” and work out the formula to get the meaning, because there is no formula.  You need to have either the code book which lists all the meanings, or else have a huge amount of encoded material which you can look through and try to puzzle out some common words and eventually work out other words’ meanings by context.  So codes are much more secure, but you’re probably going to have to lug around a big code book with you to use them since there’s no simple rule to memorise.

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Posted: 03 July 2009 03:27 PM   [ Ignore ]   [ # 2 ]
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Exactly. They’re very different things.

[offtopic]I am so stealing those for my sig.[/offtopic]

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2-15-15 9-19 1 19-16-15-18-11 7-15-4-4-5-19-19 15-6 13-9-7-8-20
Turnip Boris Yeltsin frog juggling doormat termite lizard

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