Thomas Jefferson: Cryptographer

The Wheel Cipher

http://commons.wikimedia.org/wiki/File:Jefferson%27s_disk_cipher.jpg

Thomas Jefferson, already absurdly accomplished by 1795, somehow found time to delve into cryptography, where he devised this cipher system. The letters of the alphabet are printed along the rim of each of 36 disks, which are stacked on an axle. One party rotates the disks until his message can be read along one of the 26 rows of letters, somewhat like a modern cylindrical bike lock. Now he can record the letters in any one of the other 25 rows and send that string safely to another party, who decodes it by reversing this procedure. If the message is intercepted, it’s useless even to someone who has the disks, because he must also know the order in which to stack them, and 36 disks can be stacked in 371,993,326,789,901,217,467,999,448,150,835, 200,000,000 different ways.

This is pretty robust. The cipher below, created in 1915 by U.S. Army cryptographer Joseph Mauborgne, has never been solved. “The known systems from this year (or earlier) shouldn’t be too hard to crack with modern attacks and technology,” writes NSA cryptologist Craig P. Bauer. “So, why don’t we have a plaintext yet? My best guess is that it used a cipher wheel” like Jefferson’s.

mauborgne cipher

(L. Kruh, “A 77-year-old challenge cipher,” Cryptologia, 17(2), 172-174, 1993, quoted in Bauer’sSecret History: The Story of Cryptology, 2013.)

Some Things You Just Have to Know

The 'fact' about the stars in the sky being so far way...  Is flat out incorrect!  These are Milky Way galaxy stars (where we live) and they aren't that far away.  Most stars live millions to many billions of years.  The furthest star you are going to see, with your eyes, are, at most, ~10000 light years distant.  That's not very long in star time!

The most stars you can see with your naked eye is about ten thousand of them...roughly the number of grains in a handful of sand.  This is only the smallest fraction of the number of stars that are.  The number of stars that are  is greater than all the grains of sand on all the beaches on earth.  - Carl Sagan

 

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