A 16th century French diplomat, Blaise de Vigenere, created a very simple cipher that is moderately difficult for any unintended parties to decipher. It is somewhat like a variable Caesar cipher, but the N changed with every letter. You would "encode" your message with a passphrase, and the letters of your passphrase would determine how each letter in the message would be encrypted.
This is the exact opposite of a "Variant Beaufort." To do the variant, just "decode" your plain text to get the cipher text and "encode" the cipher text to get the plain text again.
If you wanted even more security, you can use two passphrases to create a keyed Vigenere cipher, just like the one that stumped cryptologists for years. Again, a pretty simple trick, but it can ensure that your message is even harder to crack
This is a series of caches all being letterboxes, none of the hides are tough, just look in the obvious locations. Any of the micro sized containers, will not contain an ink pad, so please bring your own if you chose to stamp. Do not take the stamp or the pad, they must stay in the container.