SOLUTION to Challenge 10: No Cheating

Congratulations to Stackexchange user M Oehm, who was the first to solve NO CHEATING. It took him one day, which means he is awarded 1 point on the Leaderboard.

I’ll reveal the secrets below, but if you haven’t tried your hand, read this first.

The ciphertext:

WXYCNW LAHWNZ WONSNI LEXAPE OSMWOW RCSRQC AZ

And the original puzzle description:

Today’s cipher is a famous cryptographic method known for its economy, ingenuity, and difficulty in cracking. Its inventor created all sorts of cool things, including musical instruments, a timepiece especially useful at the North Pole, and the earliest ancestor of the Oculus Rift. Aside from this cipher, which does not bear his name, he is most famous for co-inventing a means of communicating at long distances.

The key to unlocking the mystery is his name. Good luck!

The solution:

The title “NO CHEATING” was meant to lead you to the Playfair cipher, created by Charles Wheatstone in 1854. He invented all sorts of cool things, including the English Concertina, the Polar Clock, the Stereoscope. He co-invented telegraphy, a means of communicating at long distances.

The key is CHARLESWHEATSTONE. You make a 5 by 5 square and fill it with the letters of the alphabet, starting with the key.  This gives the following square:

C H A R L
E S W T O
N B D F G
I K M P Q
U V X Y Z

Since our square only has 25 spaces, we must do away with one letter. In this case, that letter was J.

We follow the rules of the Playfair Cipher to get the message:

AM UR DE RH AS GU ST BE EN CO MX IT TE DA TS AL TH IL LX

If we take out the padded Xs and convert the G* to a J, we get the fully decoded message:

“A murder has just been committed at Salt Hill.”

… which is the first line of an early telegraph that helped catch a murderer. It was the first arrest ever made using the technology.

* Usually J is encoded is I, but I made a mistake and coded it as G here.


With CodeAWeek.com, I hope to release one cipher, puzzle, or mystery every 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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