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Pooh-Bah
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Pooh-Bah
Joined: Jan 2001
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I don't know if anyone's interest here in words extends to cryptography or not, and furthermore this is old news (more than 10 years), but there is an interesting sculpture at the CIA headquarters in Langley, VA that features a lengthy encoded message. (Its four parts have apparently been decoded already by skilled amateurs.) See http://www.elonka.com/kryptos/KryptosAerial.html and http://www.elonka.com/kryptos/KryptosAerial.html. (You can also search Google for Krytpos and find lots of stuff.) For a code/cipher challenge that does not require a Ph D in applied mathematics, check out http://www.cryptex.org/hidden.html.
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Joined: Mar 2000
Posts: 11,613
Carpal Tunnel
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Carpal Tunnel
Joined: Mar 2000
Posts: 11,613 |
Wheatstone's remarkable ingenuity was displayed in the invention of cyphers which have never been unravelled, and interpreting cypher manuscripts in the British Museum which had defied the experts. He devised a cryptograph or machine for turning a message into cypher which could only be interpreted by putting the cypher into a corresponding machine adjusted to reproduce it.
The Playfair Cipher The Playfair cipher is a substitution cipher bearing the name of the man who popularized but not created it. This method was invented by Sir Charles Wheatstone, in around 1854, however he named his invention after his goodfriend, Lyon Playfair, the first Baron Playfair St. Andrews. Wheatstone named this method after his friend, because he was more well known to the public. Playfair was a scientist and a public figure of Victorian England. He also was "at one time or another deputy speaker of the House of Commons, Postmaster General, and President of the British Association for theAdvancement of Science". Playfair demonstrated what he called "Wheatstone's newly discovered symmetrical cipher", at a dinner in January of 1854, to associates in the British Aristocracy as well as in the Foreign office. The Playfair cipher was developed for telegraph secrecy and it was the first literal digraph substitution cipher. It was used by Britians forces in the Boer War and World War I and also by the islands of Coastwatching in Australia during World War II. This method is quite easy to understand and learn, but not that easy to break, because you would need to know the "keyword" to decipher the code. The system functions on how the letters are positioned in relationship to a 5x5 alphabet matrix. A "KEYWORD" sets the pattern of letters with the other letters entered in the cells of the matrix in alphabetical order (i and j are usually combined in one cell). For instance, suppose we use the keyword "charles" then the matrix would look like this:
c h a r l
e s b d f
g i/j k m n
o p q t u
v w x y z
Now supposing the message to be enciphered here is "the scheme really works".
First of all the plaintext is divided into two-letter groups. If there are double letters occuring, in the message, either an 'x' will be used to seperate the double letters or an 'x' will be added to make a two-letter group combination. In our example, the phrase beomes:
Encipered text: th es ch em er ea lx ly wo rk sx
Each of the above two letter combinations will have 3 possible relationships with eachother in the matrix: they can be in the same column, same row, or neither. The following rules for replacement should be used:
If the two letters are in the sme column of the matrix, use the letter below it as the cipher text (columns are cyclical).
If the two letters are in the same row of the matrix, use the letter to the right as the cipher text (rows are cyclical).
If neither the same column or row, than each are exchanged with the letter at the intersection of its own row and the other column.
From our example:
Plain text: th es ch em er ea lx ly wo rk sx
Cipher text: pr sb ha dg dc bc az rz vp am bw
For deciphering, the rules are the exact opposite. http://chem.ch.huji.ac.il/~eugeniik/history/wheatstone.html
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Pooh-Bah
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Pooh-Bah
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Jackie, you are either very conversant on the Playfair cipher or else you did what I did and googled Wheatstone. Excuse me, you GoogledŽ Wheatstone. I labored for about a week with the cipher, and ultimately discovered that a small error in my reading of the ciphertext to begin with was holding me back. (What I thought was an "I" was, on closer inspection, an "F.") Of course you must never underestimate the vital importance of guessing the key to the cipher.
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