Ciphers are a common way of encrypting coordinates and indeed any information you wish to protect. Of course, this could lead to people knowing that you are trying to protect information - some people will use red herrings to prevent you finding out what you are protecting - these will lead you astray from the correct answer - others will present the information so it looks innocent and you don't look for what is hidden
There are several ciphers commonly seen in puzzle caches and some of the more common are -
The Masonic code - (or Pig Pen) - positioning the letters of the alphabet within a pattern
The Caesar Cipher - Move the characters of the alphabet by a number of places - so that J becomes W - in the standard ROT13 (Rotating them 13 places)
Pig Pen and Caesar are common enough that you can read them without a crib sheet after a while - of course, things get tougher
The Enigma code - Usually presented with enough information that you can set up an enigma emulator. The Enigma was a type of enciphering machine used by the German armed forces to send messages securely. This was famously cracked by Alan Turing.
The Vignere Cipher - A stage on from Caesar you rotate the alphabet each time, according to a key word or phrase
You can't work these out without extra clues, and they both have weaknesses The enigma never used the same letter as itself and knowing this, the decrypt analysts could turn ESWQ-PUVV-RGFQ-GMDG-KVVI-FOZS into a message by working out that it was an army code on an M3 Umkehrwalze B using Walzenlage IV I and III with the RingStellung set at RED, GrundStellung at ABK and no hot plugs set. They knew the callsigns of the units and so it gave them "Cribs" to start decoding.
A lot of increases in cryptography have been accelerated by war; necessity being the mother of invention; and by political pressure (such as the cold war).
The maths involved gets phenomenal (do dooooo de do do) (sorry, damned muppets!).
RSA encryption is current. It is called a public-key encryption system that uses very large prime-numbers - (really really large ones usually referred to as p and q) - by multiplying them together you get another insanely large number which you send out as your public key. The prime numbers are kept secret at all times. The encryption is symmetrical in that you can encrypt and decrypt in both directions. The maths for decryption starts with φ(n) = φ(p)φ(q) = (p - 1)(q - 1) = n + (p + q +1). This is actually quite simple. Although you also need to calculate the mod from d as d ≡ e+ (mod φ(n)).
If you used -p as 34399091,245322,158415736,266251387,57153 and -q as 166726871,21520366,85320565,267037805,42065 for generating a public key then if you followed the maths correctly then cf7e4f4d05561afb432edd7ceb1cd5ab47f45df251a6a29e89659b80fcef0c6b would give you plaintext. See the article on a common website for help in this.
Of course; as mentioned earlier; distractions from the truth may be employed.
In world war II a plan code-named Operation Mincemeat was carried out allowing the Axis nations to believe they had intercepted top-secret plans for the invasion of Tunisia and Greece. This was wholly successful. Germany diverted troops to defend against the plan. Be it for fun, war, or finance encryption is here to stay. Along with all of the other ploys used for keeping secrets.
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