SotD Concepts: The Jack's Lantern Code (Patreon)

As I said under one of the Speak of the Devil pages, the Jack's Lantern code was totally solvable if you knew what kind of cipher was needed to crack it. Well, if you're up to date on reading the comic, we now know the solution, but I wanted to go over how it got solved here anyway!

The code is cracked using a Vigenère cipher!

(Image from Wikipedia)
To solve this, you need: A square chart for all the letters (seen above), a similar square chart for all the numbers 0-9, and the two keys: Welcome, 0813

I hinted at the keys in the comic by having Dex say everything written by hand is part of the code, even the date.

Let's just focus on the letters for the explanation.
For the first letter, we have an S from the scrambled code, and W from the keyword "Welcome"

You go down to the row that starts with the first letter in the key "W" and then find the first letter in the code "S" in that row. Once there, you go up to the top to find what the real letter is, which just happens to be "W" again.

You do this for every letter in the code and corresponding letter in the key, for instance the next letters to match up would be "Y" for the code and "E" for the key.

If you run out of letters in the key, you repeat it like: welcomewelcome, so then the "N" in the code would match up with the letter "W" (resulting in the R in the word "Street")

For the numbers, you just do this same system but with a number chart, using the date as the keyword.

Using this system, the solution translates:
0 8 3 0 . S . Y T Q B . E X N I P V . V M X S Q K M C
into:
1 1 3 8 . W . U I O N . S T R E E T . H A T H O W A Y

As you can see, even when a letter is repeated, like in "STREET", the code becomes too scrambled to decipher without the keyword.

So there it is! Hope you enjoyed seeing how I made this code, even if it was relatively unimportant.