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Cryptology 101: Rail Fence

A cache by yukionna Send Message to Owner Message this owner
Hidden : 7/19/2009
2 out of 5
2 out of 5

Size: Size: regular (regular)

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Geocache Description:

The cache is not located at the posted coordinates. You must decipher the ciphertext, in the Puzzle section below, to obtain the actual coordinates of where the cache is hidden. The posted coordinates are the suggested parking area with room for two cars. Please don't block the gate.



This is another cache in my series of cryptology puzzle caches with the goal of demystifying some of the techniques used for solving and creating puzzle caches.

This puzzle cache is a transposition cipher called Rail Fence. In the rail fence cipher, the plaintext is written downwards and diagonally on successive "rails" of an imaginary fence, then moving up when the bottom rail is reached. When the top rail is reached, the message is written downwards again until the whole plaintext is written out. The message is then read off in rows.

For example, if we have 3 "rails" and a message of "THE CACHE IS UNDER THE BIG ROCK", then the message is set-up as follows:

T . . . A . . . I . . . D . . . H . . . G . . . K
. H . C . C . E . S . N . E . T . E . I . R . C .
. . E . . . H . . . U . . . R . . . B . . . O . .

The three rows are read off one by one and grouped in any order. In this example, I grouped them in three groups -- each grouping depicts a rail -- which makes this puzzle easier to solve.


I could have grouped the letters in groups of four which would make the cipher a little bit more difficult to solve because the number of rails wouldn't be as straightforward:


Transposition ciphers like this one are easily decrypted as the number of keys (i.e., the number of rails) is usually between three and seven so that different solutions can be quickly tried and deciphered.


Decipher the following rail fence cipher to obtain the coordinates to where the cache is hidden. Good luck and have fun!

North Coordinates


West Coordinates


You can check your answers for this puzzle on


The cache is a 6" x 8" clear plastic lock 'n lock located in the John D. Eaton State Forest in East Kingston, NH. The hike into the cache is along a logging road in the Eaton State Forest which is located next to the Hog Hill Swamp area.

Additional Hints (Decrypt)

Qba'g trg fghzcrq

Decryption Key


(letter above equals below, and vice versa)



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Coordinates are in the WGS84 datum

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