Rules for this puzzle: No intentional red herrings, no oddball (fishiness) methods of presenting coordinates (UTM, for example, or also having coordinates read backwards), and no leaving off the N32 and W97 just to make it more difficult. There may be more than one layer on this puzzle. Collaboration is allowed and you may ask me for hints after there has been a FTF.
I could do an entire series based on ciphers. In fact, many people have. As such, it is kind of difficult to summarize ciphers; however, I will take a crack at it.
CAUTION:
RAMBLINGS AHEAD!
For my examples, I'm going to use N32 45.123 W097 21.456, or more specifically, North Three Two Degrees Four Five Point One Two Three West Zero Nine Seven Degrees Two One Point Four Five Six
In a traditional sense there are two types of ciphers; monoalphabetic and polyalphabetic. A monoalphabetic cipher is a simple substitution cipher where each letter in the cipher corresponds, exactly, to another letter. A Caesar cipher, or Rot13, is a monoalphabetic cipher. If I encoded my coordinates above with a Caesar cipher it would look like this:
Abegu Guerr Gjb Qrterrf Sbhe Svir Cbvag Bar Gjb Guerr Jrfg Mreb Avar Frira Qrterrf Gjb Bar Cbvag Sbhe Svir Fvk
A polyalphabetic cipher is one where the alphabet changes as you move forward from one character to the next in the message. Vigenère is an example of a polyalphabetic cipher. A Vigenère cipher, without a password, basically follows a Rot1 through Rot26 rotation and then loops. So, the first letter would be Rot1, the second letter would be Rot2, so on and so forth. Now, that in itself isn't going to be very hard to break, so traditionally, a Vigenère cipher also incorporates a key. The key indicates which letters the alphabet starts with (instead of abcde, etc). Thus, if the key were "key", then the rotating alphabet is keyabcdfghijlmnopqrstuvwxz. That makes it a bit harder to decrypt (but not impossible). A sample Vigenère cipher, encoded with my mystery key, is as follows:
Ycknz Evkyw Ekh Xwrfxyk Qcnl Xtjx Jgtbm Ifp Hpi Lsfxy Opgm Twcc Gcfp Gxpwy Rxajpsl Noz Cgy Hzwgn Xzik Zags Lcp
So, the above two strings probably look like random letters to the naked eye. Fortunately, they are not! There is a tool, called Index of Coincidence, which can be used to determine if a cipher is a mono or poly alphabetic cipher. I like to use this site, Dcode.FR, for testing ciphers
If I put in the top string, it reports an index of 0.08772. If I put in the bottom string, it reports an index of 0.04912. Now, this isn't a perfect science, but an index below 5 is probably a poly cipher. An index above 5 is probably a mono cipher. The English language, in general, will report about 0.0667. Random text, in general, will report about 0.0385. This tool can be very helpful in determining how to break a cipher - assuming the CO did not leave you any clues.
For just about any monoalphabetic cipher you can use a substitution cipher technique to crack it. For example, check out this substitution cipher solver. Drop in our monoalphabetic string and specify English as the language. It will probably fail, but I bet it solves enough of the string for you to make an educated guess on the real solution.
If you can identify a cipher as mono, you can probably decrypt it without ever knowing what the cipher is. Atbash, Affine, or even random ASCII characters or picture symbols will all succumb to this code break. There are even some special tools for fancier mono ciphers such as Rail Fence on Dcode.FR.
Now, with poly, it gets more complicated; however, some similar techniques can be used if you happen to know what the cipher might be. For example, take our bottom string and go to this Vigenère cipher decoder. I haven't told you my password, but try dropping in the string, select "knowing a plain text word", say "North", and then click decrypt, Guess what? You have now cracked a cipher and you know my passkey! The nice thing about Geocaching ciphers is usually there are some very guessable words in them.
The website, Dcode.FR, will let you try this method with a variety of polyalphabetic ciphers such as polybius square or enigma. It doesn't always work, but if you happen to know the cipher type, sometimes you can get enough plain text from the decryption to figure out what needs to truly be done to crack the cipher.
I highly recommend making yourself familiar with Dcode.FR, Geocaching Toolbox, and Rumkin if you are interested in solving more ciphers.
So, there you go, some very basic cipher cracking techniques in a nutshell. You should now be able to solve this bonus cache... I feel like, perhaps, I'm forgetting to tell you something... hmm... maybe it will come back to me later.
Good luck and I hope you enjoyed this series!
Puzzle Solving Tools - If I don't discuss a particular tool below in the paragraphs above, you may assume I did not use it for this puzzle; however, it may be useful for puzzles of similar style.
You can validate your puzzle solution with certitude.
A NOTE TO PUZZLE COs: Ciphers can be lots of fun or a huge headache to solve. Especially if multiple layers are used and each layer is a different cipher (or even the same cipher). The problem with using multiple layers on ciphers is that you don't actually know, for sure, that a layer has been correctly decoded until the end. As such, when I do multiple layers with ciphers, I always make sure there is a few words of plain text that get decoded with each layer. For example, after decoding one layer with Caesar the second layer might say "SUCCESS eiudnj vwf jtyijorn dbjfehuuefnj" - this lets your solver know they are on the correct path.