Exploring Puzzle Caches – Part 3

If you have been following along, you know I’m currently working on a large puzzle series called A Lesson In Ciphers. I figured for part three of my Exploring Puzzle Caches articles (well, part four if you consider I did a Night Cache article already), I thought I would talk about how to put together a cipher cache. Grab those pencils and papers everyone, it’s ciphering time.

Ciphers are one of the oldest methods of encryption, dating back to the ancient Egyptions.  The Egyptions didn’t have supercomputers to work with, so their ciphers look primitive compared to what we have today.  But the basic principle stayed the same.  Start with a message.  Change the symbols using a defined method.  End with a cipher.  Seems simple enough…right?

But before worrying about the cipher itself, first you need to hide the cache.  Pick one of those spots you’ve been eyeing for a while.  No, not THAT one.  Okay, that spot over there might work.  Go place the cache and grab your coordinates.  Nah ah ah…grab more than one.  You don’t want to take all the time building the message only to find out your coordinates are twenty feet off.   Now, average the coordinates and get your final location.  Good.  Let’s go.

Wait, don’t forgot to pick a bogus starting spot.  I vary mine.  I may use a nearby parking area or I may pick an arbitrary spot within two miles.  Why two miles?  Groundspeak recommends that you keep bogus coordinates within two miles.  Some reviewers stick closely to that recommendation, others are a bit more lenient.  I’ve tried to stick to the two mile limit so that cachers at least have an idea of what general area of town my caches are in A two mile radius still leaves a pretty wide area of possibilities, but it’s better than a ten mile radius.  Lately, I’ve been picking spots in the middle of a major intersection that’s nearby or in the middle of a body of water.  Okay, on to the cipher.

After figuring out the coordinates to your final location, you need to put them into a message.  For almost all ciphers, you’ll need to write out your coordinates with words, so that’s a good starting spot for the message.  It’s up to you on whether to write 900 as nine hundred or nine zero zero.  Once you have your coordinates written out, then decide whether to make them the message, or make them a part of a larger message.  I would recommend avoiding entire paragraphs written around your coordinates unless absolutely necessary.  Nobody wants to decipher a message on how you named the cache after the pet cat who died when you were ten.  Outside of the coordinates, I’ve sometimes added in a description of what type of container it is, or a hint on how to find it.  Something worthwhile for the cacher.

Let’s look at a few words before you build the cipher.  Plain text (PT) and cipher text (CT) refer to the original message and the enciphered message, respectively.  Then, you have the plaintext alphabet (PA) and the keyed alphabet (KA).  I’ve heard keyed alphabet refered to as cipher alphabet as well.  The PA is merely the normal alphabet A – Z.  The KA is the same, with a keyword thrown in.  The keyword is a randomly assigned word that when put into the KA, it alters the arrangement of the letters away from the normal A – Z format.  Back to your cipher.

So you have your PT figured out.  Next, you need to figure out what method you want to use for enciphering the message.  You are likely familiar with one method already, the ROT13.  This is the method used to encipher the hints on the Geocaching website.  The PA is written out, then sliced in half.  The two halfs are laid out one above the other as such:

a b c d e f g h i j k l m
n o p q r s t u v w x y z

Simply designed, A = N & N = A, and so on.  It is a basic substitution cipher, where you substitute one letter for another.  Yeah, I know.  DUH!  But it’s important to know that there are many different types of substitution ciphers that range in difficulty.

Now, let’s look at one more example of writing out the PA, along with a KA.  This time, let’s use a keyword.  We’ll use WORDPRESS as our keyword.  When using a keyword to build a KA, you first write out the word.  Only use a letter once.  For our example, WORDPRESS will become WORDPES.  Now, after writing that out, continue with the rest of the alphabet, again taking out letters that were part of the keyword, like so:


Now, before we do anything else, you need to realize that when you line up the PA with your new KA, the final letters will equal themselves. To avoid this, let’s shift the KA over, wrapping the letters at the end back around to the beginning. We’ll shift it five characters, like so:


Now, line it up with your PA:

PA: a b c d e f g h i j k l m n o p q r s t u v w x y z
KA: u v x y z w o r d p e s a b c f g h i j k l m n q t

You know have the tools needed to change your PT into the CT. Let’s say that all you did with your PT is write out the coordinates. You’ll start changing the letters using your two alphabets. N would become B, O becomes C, R becomes H, T becomes J, H becomes R, such that NORTH would become BCHJR.  Continue on from there and you have just built what is called a Keyed Ceasar cipher. Now, all you have to do is put together the cache page, along with your ciphered message, and you have created a cipher cache.

There are many ways to build a substitution cipher.  Each one with different rules for how to encipher the text.  Only research will help you learn some of the methods.

But way, there’s more.  There are also transposition ciphers.  In these types, instead of substituting one letter for another, you instead write out your PT.  Then, you rearrange the letters or words.  Take the message THE BRITISH ARE COMING.  You could write your CT by alternating letters: tertsaeoighbiihrcmn.  You could hop from front to back until you reach the center: tghneibmroicteirsah.  You could write each word out on a separate line and write the message in order top to bottom, left to right: tbachrroeiemtiinsgh.  These are just a couple of quick methods.  Again, with some research, you’ll learn that there are a lot of already established methods developed over the history of ciphers.

So just where can you go for help?  Well, Wikipedia does provide some help starting with their entry for Ciphers. After that, I’ll provide one other useful website for most basic ciphers. It is called Cipher Tools and it not only has information on some popular cipher methods, but it can even help with enciphering and deciphering messages. It might be useful the next time you come across a cipher cache.

Well, that covers the basics of how to build a cipher. I’ll leave you to decide which method to use.


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2 Responses to Exploring Puzzle Caches – Part 3

  1. GeoJoe says:

    Thanks for this post. Knowing how to create these might actually help me do a better job solving them – something I often struggle with. Thanks for the useful information.

  2. Pingback: Geocaching Carnival - Issue #3 | The Geocacher

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