A Theoretical Dive Into the Book Cipher

Question

The following code, of my own making, follows a well-known, standard procedure. However, it may be interesting to note that there is something unique about it. Try and break it---it will probably be easy, but the theory of what happens is pretty neat. Follow the instructions you find on the way. The answer will be a generic group of three words. (Disregard all that comes before this colon in your attempts to solve this puzzle.):

"12 32 18 8 14 68 69 27 52 43 5 17 3 40 75 7 79"

"Mind turned to puzzles, labyrinthine gambits, reacquisition, tempi, Chess. He moved unbeknownst, warriors hypervigilant, forming an epic, enigmatically, a story. His game was a code, an abstract, a cryptic pattern. A seer only could decode his attacks; they are solveproof. To see transliterated, to speak strange words might puzzle, but alas, straightish in truth was the way to find answers. As the puzzle seems all too much eschew; literati overthink. Do not, his last envoi, is what he said. He addresses those who search, that this, what you now hold, is the book for the code. Later (much later), he says, when one is delving for the third, begin with “The Unanimous”. Lastly, the wizard states, think not too deeply of this riddle---the words' meaning are unimportant, this passage is your key."

For help solving, try searching for the book cipher dcode.fr/en tool.

Answer 1

This is a book cipher. What is special is that depending on the key you use, you will get different messages. It was a pain to create, but the theory could be expanded to fit some really cool themes. Right now, with only a short message encrypted, it is like a prototype of the true idea.

First use the given passage (Mind turned to...key.) as your book in a standard book cipher, using the first letter of whatever numbered word, for each number you are decoding. That gives you the message:

USETHELASTLETTERS or USE THE LAST LETTERS

Then, if you do the same thing, using the same passage as your key, but with the last letters of each word instead of the first, you get:

TRYITWITHTHEDECOFIND or TRY IT WITH THE DEC OF IND

If you can work out the tricky spacing, you are prompted to decode this cipher again using the Declaration of Independence, a classic for book ciphers. As the passage states, if you start with "The Unanimous" as your first two words of the Declaration, using the first letters of each word gets you:

ITISCOMPLETEDPTUT or IT IS COMPLETED PTUT

You are done. The "PTUT" is just the leftover characters from the previous message. Isn't that neat?