- CEMC Home
- About Us
- Contests
- Courseware
- CEMC Digital
- CEMC in Person
- Books
- Master of Mathematics

for Teachers - Educator Development
- Make a Difference

Bob tries to pass a note to Alice during class. A teacher intercepts the note as it was being passed across the room. Luckily, Bob had encrypted his message using Caesar cipher. The encrypted message is shown below. Can you decipher it?

Hint: The answer from Problem 1 might help!

We know Bob has encrypted the message using a Caesar cipher. A Caesar cipher is just a cipher that substitutes each letter with another letter a fixed number of letters down the alphabet, looping around at the end. This fixed number is referred to as the key. For example, if the key to the Caesar cipher is 4, that means we substitute the letter A with D, B with E, and so on.

Now Problem 2 gives us the hint that the answer to Problem 1 might help. Let’s try 6 as our key. So A becomes G, B becomes H, and so on.

Using the table below we can see that S corresponds to the letter M, G corresponds to the letter A, Z corresponds to the letter T, and if we continue this backwards substitution, we would get the deciphered message shown below.

The encrypted message is SGZNOYGCKYUSK.

The deciphered message is MATHISAWESOME.

Therefore the deciphered message “MATH IS AWESOME” doesn't give Bob detention.