What Is The Geocache Cipher Decoder?

A popular offshoot of traditional geocaching merges puzzles and problem solving with the treasure hunting element that geocachers enjoy. Collectively, these are known as puzzle geocaching, or geocache puzzles. In some cases, these puzzles can include an element of light encryption, often using a cipher decoder.

A cipher decrypter, also known in geocaching as a cipher decoder, is a simple method of encoding or decoding a message by swapping letters. It has two rows of letters in its simplest form, A to M and N to Z. Switching the corresponding letters encodes AND decodes the message.

handwritten cipher decoder
A simple handwritten cipher decoder

How To Create A Simple Geocaching Cipher

In this simple method, a message is encoded simply by swapping letters over.

You can quickly write out a cipher chart by hand, mapping the letters to each other in a simple geocaching cipher. It only takes a moment with a pen and paper, and can be used repeatedly if you keep it safe when you’re out and about.

Once you’ve got the legend for your cipher, it’s really easy to encrypt and decrypt your messages. For example, the word GEOCACHE becomes:

G ➡T

E ➡ R

O ➡ B

C ➡ P

A ➡ N

C ➡ P

H ➡ U

E ➡ R

Put that together and your coded version is TRBPNPUR.

To decode, simply repeat the process.

What Is A Caesar Cipher?

The above example is a specific example of a Caesar Cipher. More broadly, the technique shifts letters by a number of letters called the key.

A Caeser Cipher is decoded by shifting each letter forwards (right shift) or backwards (left shift) by a set number of positions in the alphabet. The number of characters to shift is called the key. A positive key number is a right shift, while a negative number is a left shift.

cipher wheel and pen
A slightly more complex cipher requires a cipher wheel to easily decode

When Should I Use A Left Shift Or Right Shift In My Cipher?

In Geocaching puzzles, part of the point is to introduce a devious confusion into the hunt. Whether the shift in your cipher key is left or right (negative or positive respectively) is actually somewhat irrelevant.

The shift in a cipher decode is cyclic. In a 26 letter base alphabet, a right shift of 10 is equivalent to a left shift of 16. Similarly, a shift written as -10 is the same as 16 (sometimes written +16). Theoretically, a shift of 3 could even be written as 29 by a devious puzzle setter.

How To Make A Cipher Decoder Ring?

It’s really easy to get your hand on a Caesar cipher decoder ring like the one in the above photo. Ours came from a PDF printout from FrugalFun4Boys.com. What I really like about their version is that the inner letter ring (they call it the ‘Middle’ ring on the printout) can be swapped for a blank version, allowing you to put the letters in any order, or even use symbols if you’re feeling creative.

If you’re encountering a lot of geocache puzzle (or setting them!) where the letters in the encoded alphabet are randomly ordered to encode, you might wish to create a collection of the wheels with the blank middle ring. You can then quickly create them as required by writing the letters in on the fly. Alternatively use a pencil and eraser.

Are There Other Types Of Cipher?

Many forms of encryption based on cipher techniques, and historically some famous examples have been used in the military to communicate without revealing information to the enemy.

Today, you’ll be using very advanced cipher encryption every day without even realizing it. Common examples as websites with the padlock in the address bar that securely communicate across the internet and making payments with your credit and debit card in shops.

For geocaching though, it’s only basic techniques coming into play. Advanced techniques would be near impossible to manually use as part of a game, not to mention take the fun out of the activity for all but the most nerdy of participants!

What If There’s No Key?

If you find a string of text as a clue to the location of a cache, or as a message inside a cache you find, sometimes there will be no key provided. It may be that someone has removed accompanying information, but it’s more likely deliberate. The fact that a cipher is used in the first place suggests the player setting the challenge chose to add complexity for seekers, so this is just an added layer of depth.

To decode a cipher without a key, you need to spend time with a trial and error approach. Look for clues in the sequence of letters. The solution will always map the same letters from the code to the answer, and common words like ‘the’ often help you to get started.

Look for short words with double letters, as these will commonly be vowels. If you’re trying to decode co-ordinates to find a cache, then the chances are the answer will spell out numbers (in word form e.g. FOUR).

Once you’ve got a letter that you’re fairly sure you’re correct about, test a Caesar cipher to see if you’ve got a solution. For example, if your clue has a C and you think the corresponding solution letter is an E, move each other letter in the clue forward by two letters. If your solution spells out something that makes sense, great!

If you’ve got a mess of letters, you’ve either incorrectly mapped that first letter to the answer, or alternatively it’s not a Caesar cipher. In the latter case, turn to the wheel we talked about earlier with the blank section to complete.

Remember that not all puzzles with have the letters in alphabetical order on the wheel, so gradually work your way through the clue, and mark off letters as you add them to the wheel. By the time you’re done, you’ll be able to decode the clue without adding any letter to the wheel more than once. You may not need to add all letters to the wheel.


Hi, I'm Kevin. I discovered Geocaching several years ago on a family vacation at Center Parcs in the UK with my wife's family. Since then we've regularly been out and about avoiding the Muggles and hunting for caches.

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