This cache is NOT at the posted coordinates,
solve the puzzle below to find the corrected coordinates.
See Cryptogram University Series 101 CUS 101: Cryptogram Basics for more information on cryptography and this cache series.
CUS 102: Simple Substitution Ciphers will teach you about the two most common substitution ciphers used in geocaching puzzles – the Caesar Cipher and the Atbash Cipher. As you may remember from CUS 101, a substitution cipher replaces characters in a message with other letters, numbers, or symbols.
Caesar Cipher:
A Caesar Cipher is one of the simplest and most widely known cryptograms, first used by Julius Caesar to protect messages of military significance. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter that is a designated number of positions down the alphabet called a rotation or ROT. The number behind ROT is the number of letters shifted down the alphabet. For geocachers, ROT-13 Caesar Ciphers are used on every cache page to encrypt the hint (Figure 1).
Figure 1: Geocaching.com ROT-13 Decoder
ROT-13 is the simplest of the Caesar Ciphers because it is the only ROT where the letters are interchangeable for both encryption and decryption (e.g. A=N and N=A). In the ROT-3 example below (Figure 2), B=E, because E is three letters down the alphabet from B, but unlike in a ROT-13, E≠B. In ROT-3, E=H, because H is three letters down the alphabet from E.
Figure 2: Example of a ROT-3 shift Caesar Cipher
The table below shows all 25 rotations (Figure 3). The yellow letters across the top are the plaintext letters and the yellow numbers down the left side are the rotations (ROT) from ROT-1 all the way through ROT-25. In a Caesar Cipher, because there are 26 letters in the alphabet, ROT-0 and ROT-26 would both equal the plaintext letters and therefore not encrypt anything.
Figure 3: Caesar Cipher Table
An example of how to encode using the Caesar Cipher table above (Figure 3), lets encode the word GEOCACHE using ROT-20. Start by going across the yellow letters to the letter G, then go down the G column until you are at the ROT-20 row, and that will show you that G=A in ROT-20. Do this for all letters and GEOCACHE in plaintext becomes AYIWUWBY in ciphertext. To decode using the Caesar Cipher table above, start by going to the ROT-20 row, then go across the ROT-20 row until you find the white letter that you want to decode. In the previous example AYIWUWBY, you go across the ROT-20 row until you find the A, then you follow that column up to the top yellow row to find the plaintext letter G.
There are also many tools, physical and digital, that can help you decode a Caesar Cipher. The Caesar Cipher Wheel (Figure 4) comes in many different forms from geocoins and printable discs to Little Orphan Annie’s decoder ring. There are also many geocaching tool apps and websites that will quickly encode/decode a Caesar Cipher.
Figure 4: Caesar Cipher Wheel
Atbash Cipher:
The Atbash Cipher is another simple substitution cipher frequently used in geocache puzzles, first developed and used with the Hebrew alphabet in ancient Israel. The Atbash Cipher is formed by taking the alphabet and mapping it to its reverse, so that the first letter becomes the last letter, the second letter becomes the second to last letter and so on.
Figure 5: Atbash Cipher Decoder
So, for example, GEOCACHE encoded using Atbash Cipher would be TVLXZXSV.
The CUS 102 Exam:
Decode this simple substitution cipher to obtain the final coordinates.
IJMOC OCMZZ NDS ADQZ NZQZI AJPM ZDBCO ZDBCO
RZNO NZQZI NDS OCMZZ NDS UZMJ IDIZ ADQZ