The purposes of this geoart series are twofold: to bring cachers to the watershed of the North Fork of the Broad River in Stephens and Franklin Counties and to serve as an introduction to the fascinating field of cryptography.
Most geocachers are familiar with a Caesar cipher, which involves substituting each letter of the alphabet with the letter a certain number of spaces away. This is a special case of the more general simple substitution cipher, which involves substituting each letter with some other letter (or possibly even itself), without some consistent shift.
There are lots of possible ways to do this. We have 26 choices for A, 25 choices for B (since we've already chosen something for A), 24 choices for C, and so on. Multiplying these together, we have 26×25×24×···×3×2×1 = 26! (or 26 factorial).
If you plug this into a calculator, you'll see that 26! is about 4 ×1026, i.e., a 4 followed by 26 zero's. That's 400 septillion!. Let's try to put this in perspective. If you tried one possible simple substitution cipher every second, then it would take 1.3×1019 years to get through them all. How long is that? Take the current age of our universe (13.8 billion years), and multiply that number by over 920 million!
With this information, it may seem like cracking a simple substitution cipher is impossible! But fortunately, there are some tricks to make the process much smoother. For example, E is the most common letter in the English language, appearing about 12.7% of the time. So there's a pretty good chance that whichever letter appears most frequently in the encrypted message corresponds to E. You can also look for bigrams, i.e., pairs of letters. The most frequently occuring English bigram is TH, appearing 2.9% of the time. This process of looking for common letters in the encrypted message is known as frequency analysis.
In fact, you may be familiar with simple substitution ciphers already from the puzzle section of your daily newspaper. The "Daily Cryptoquote", which always begins with the example, "AXYDLBAAXR is LONGFELLOW," involves exactly this sort of cipher.
To find this geocache, decrypt the message below using a simple substitution cipher.
YKVAJ AJRVA NDKUV AXIYA NYRYI YRYIW RMFIV KXIWA IRCJA NAJVI IIRCJ AIIYK YIWRM DROI
Congratulations to bbatch6 and cactuslover for FTF!