THE CACHE IS NOT AT THE
POSTED COORDINATES!
The posted coordinates are close to many
ideal parking spots.
I recently finished hosting a week long Cryptology Camp for
middle and high school students. My students decided to test their
skills by creating a geocache that would showcase some of the
classic ciphers we studied. This is a five stage puzzle cache
that will require you to decipher the coordinates for the next
stage at each stop. No coordinate checker is necessary... if
you use the correct decryption technique you will know it!
The purpose of this geocache is to familiarize you with some
classical cipher techniques. Who knows... they may come in
handy on other unknown geocaches. There are now web applications
which can quickly decipher many of these classical ciphers. You
could save yourself a lot if you can access the web on site.
HOWEVER... if you want to LEARN SOMETHING from this quest, leave
the smart phone in your pocket and take out the clipboard for a
change. If you really want to get in the mood, bring along a WW1
army hat and imagine yourself in the trenches deciphering your
orders!
All stages are hidden within short walking distance of posted
coordinates around the Upper Leacock Township Building. Please
NO NIGHT CACHING! The best time to seek this cache is in the
evening or the weekend. There is a police substation located at the
township office and any suspicious nighttime activity will not go
unnoticed. The first four stages are micro and the final is a small
size lock-n-lock. NSA pin from the National Cryptologic Museum for
First-To-Find!
Recommended Equipment List:
• Clipboard
• Several sheets of paper
• Pencil/Pen
• Knowledge of 5 specific classical ciphers
• The Gettysburg Address
Only if deciphering stage 1 coordinates on site
• Patience
The Ciphertext:
T D M L A I D J Y Z N I K T B N J D I P L H O L C X
I W T J H M B W L V K T Q L V N E H A R M A S P M W W R I C H N C S
S Z J J J
A Little Help:
Coordinates for Stage 1: Book Cipher
A book cipher is a cipher in which the key is part of a well
known book or other text. Traditional book ciphers referenced the
location of specific words in a given text. However, in our book
cipher we used a letter-by-letter approach. To encrypt the location
of this cache the coordinates were spelled out letter-by-letter
above the opening lines of the Gettysburg Address. The pairs
of letters were then added to create the ciphertext. For example: C
+ H = K. If the sum of the two letters was more than 26 the letter
of the cipher text was determined by taking the remainder when the
sum was divided by 26 (i.e. just cycling back through the
alphabet). For example P + T = J. To decrypt the coordinates for
stage 1 line up the text of the Gettysburg Address underneath the
above ciphertext and subtract. By the end of this exercise you
should be pretty good a modular arithmetic!
Gettysburg Address
Coordinates for Stage 2: Keyword Cipher
A keyword cipher is a simple substitution cipher in which
the key is determined using the letters of a keyword. The letters
of the keyword is spelled out underneath the english alphabet,
without any repeated letters, followed by the unused letters in
alphabetical order.
More Information
Coordinates for Stage 3: Playfair
The Playfair cipher, named after Lord Playfair who popularized
its use, was used by the British in WW1 and the Germans in WW2. It
is a digraph substitution cipher in which pairs of plaintext
letters are replaced with pairs of ciphertext letters. In order to
unlock the coordinates for this stage you will need to set up a 5x5
grid of letters using the keyword provided with the ciphertext and
familiarize yourself with the rules for deciphering each pair of
letters. Since there are only 25 spaces in which to fit the 26
letters of the alphabet "I" and "J" share the same
position.
More Information
Coordinates for Stage 4: Vigenere Cipher
The Vigenere cipher is a polyalphabetic cipher which can
be deciphered by hand. To unlock the coordinates for this stage you
will need a copy of the Vigenere Square and the keyword which is
provided along with the ciphertext at Stage 3. Make sure you read
up on the technique for deciphering a Vigenere ciphertext.
More Information
Coordinates for Final: ROT Cipher
A ROT cipher is a simple substitution cipher in which the
key is determined to shifting or ROTating the letters of the
alphabet a fixed number of letters. How far was the alphabet
rotated to encrypt the location for the final stage?... that is for
you to find out! A cipher disk certainly would help!
More Information
7/30/10 - Congratulations FTF
ratjam & AirSoftGunner