Cipher Wall

Can you break level 1?

Can you break level 2?

Can you break level 3?

The cipher wall uses three different ciphers, which we have called the Shift cipher, the X cipher, and the Combo cipher.

The Shift cipher, also known as a Caesar shift, works by shifting the alphabet across. So, a shift of three looks like this:

You can break a shift cipher by trying all 26 possible ways of shifting the alphabet. A shift of three is like adding 3 to the position of each letter. So, the first letter of the alphabet (a) becomes the fourth letter (D), the second letter of the alphabet (b) becomes the fifth letter (E), and so on. Near the end of the alphabet, adding three will give values of 27, 28 and 29. This is larger than the alphabet, so the numbers wraparound to 1, 2 and 3. This is like adding on a clock, but the clock has size 26.

The X cipher works by multiplying the letter positions by a value. This is what happens when we multiply by 3:

This time, the first letter of the alphabet (a) becomes the third letter (C), and the second letter (b) becomes the sixth letter (F). Some values don’t work as an X cipher, for example see what happens when we multiply by 4:

When the multiplication value shares a factor with 26, some code letters will appear more than once, which is not allowed. For that reason, there are only 12 valid X ciphers which are 1, 3, 5, 7, 9, 11, 15, 17, 19, 21, 23, 25. So it is even easier to break the code by checking all the possibilities.

The combo cipher, also known as an affine cipher, encrypts messages twice! First with an X cipher, followed by a shift cipher. For example, we could multiply by 3 then add a shift of 5. For each of the 12 possible X ciphers, there are 26 possible Shift ciphers. Altogether this makes 312 possible combo ciphers. It’s now a lot harder to check all the possibilities, so you may need to look for some clues. For example, are there any one letter words? What could they be? Now try to adjust the X and shift controls to decrypt that one letter word. For each X cipher, there will be exactly one shift that will do it, so you no longer need to check every possibility.