SOLUTION to Challenge 3: A Simple Calculation

Congratulations to Euchre Mutt for being the first person to solve Challenge 3!  The puzzle remained unsolved for a whopping 134 days … a site record! … which means he is awarded 134 points on the Leaderboard.

If you haven’t tried your hand at solving it, read this first.

Here’s original description and ciphertext:

With this cipher, I hope to add a new encryption method to the playbook. If you formulate the correct hypothesis, you just might take away the prize.

Some clues:

  1. It’s a substitution cipher.
  2. The ciphertext is 102 characters. The plaintext solution is 34 characters.
  3. What is 102 divided by 34, and what does that tell you?
  4. The plaintext solution is a quote from a famous mathematician.

The ciphertext is:

LCFBPDLED HCJJKAHFF TSNIGANRK GMBHJMQCO XETSSRVLZ CFDZOWVLP JJKFSRPCK BXFIVPWJO RSLYNXFSD HRHAOKQQK IJAEPFBUI QPZ


The key to solving this cipher lies in a very simple mathematical formula. It’s so simple that you’re going to kick yourself for not figuring out.

First, number the alphabet, where A=1, B=2, C=3, etc.

Now, space the ciphertext into blocks of 3 characters and apply the following formula to each block: A+B-C

The result of that formula is one plaintext character. Apply the same formula to every block of three characters, and you’ll discover the solution.

For example, if we apply it to the first three characters “LCF” …

L+C-F=

12+3-6=9

9=I

Continue down the line to get the solution:

“In math, you’re either right or you’re wrong”

… which is a quote by NASA mathematician Katherine Johnson. Johnson was profiled in the book and film Hidden Figures.

There are a couple of hints in the challenge description, which I’ll put in bold here:

With this cipher, I hope to add a new encryption method to the playbook. If you formulate the correct hypothesis, you just might take away the prize.


With CodeAWeek.com, I hope to release one cipher, puzzle, or mystery each week. Anyone can attempt to solve. The winner is the first person to send a correct solution and a description of the solve method to codemaster@codeaweek.com. Once a correct solution is e-mailed, I will publish a follow-up post, congratulating the winner and revealing the secrets of the code.

You may post questions or theories in the comments, but DO NOT POST SOLUTIONS. E-mail them to codemaster@codeaweek.com.

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