![]() ![]() Because this would leave certain highly sensitive words exposed, such words would first be concealed by code. This worked much like an ordinary route cipher, but transposed whole words instead of individual letters. Badly chosen routes will leave excessive chunks of plaintext, or text simply reversed, and this will give cryptanalysts a clue as to the routes.Īn interesting variation of the route cipher was the Union Route Cipher, used by Union forces during the American Civil War. ![]() In fact, for messages of reasonable length, the number of possible keys is potentially too great to be enumerated even by modern machinery. Route ciphers have many more keys than a rail fence. (The clerk has broken this ciphertext up into blocks of three to help avoid errors). The key might specify "spiral inwards, clockwise, starting from the top right". For example, using the same plaintext and grid that we used for rail fence: In a route cipher, the plaintext is first written out in a grid of given dimensions, then read off in a pattern given in the key. Transposition cipher code#Since there are 30 letters, and we know there are 3 rails, we divide the group into 3 groups of 10.ģ) Finally, write down the first letter from group 1, from group 2, and group 3, followed by the second letter from group 1, group 2, and group 3, etc.Ĥ) Now just break the string of letters into easily identifyable words, separate the nulls, and the code is deciphered. The easiest way to decipher a rail fence cipher is to use the following method:ġ) First, run all the letters into a long string.Ģ) Next, divide the string of letters into a number of even groups equal to the number of rails. ![]() The rail fence cipher is not very strong the number of practical keys is small enough that a cryptanalyst can try them all by hand.See also scytale (Grouping letters into blocks of a standard size, typically five, was a practice developed for ease of transmission by telegraph.) The extra odd letters at the end are "nulls", added to round off the pattern, or to confuse a cryptanalyst. For example, if we have 3 "rails" and a message of 'WE ARE DISCOVERED. In the rail fence cipher, the plaintext is written downwards on successive "rails" of an imaginary fence, starting a new column when we get to the top. ![]()
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