## On the Subject of the Blue Cipher

Blue is often to describe sadness. Luckily for you, this cipher will cheer you up.

On the module, you will see 3 screens, a keyboard, 2 arrows, and a submit button that displays the current page you're on.

Pressing the right arrow takes you to the next page. Pressing the left arrow takes you to the previous page. There is a total of 2 pages.

On page 1, the top screen shows a 6 letter encrypted word, the middle and bottom screen shows an 6 digit number.

On page 2, the top screen shows a word.

### Step 1: Tridigital Cipher

First thing you need to do is create a key. To do so, take the keyword from the top screen of page 2 and remove any duplicate letters from the keyword (keep each letter’s first occurrence). Take the entire alphabet and remove any letters that is shown in the keyword.

If the number of indicators is even, place the alphabet at the end of the keyword. Otherwise, place the alphabet at the beginning of the keyword.

Then arrange the key you made by splitting the key into 3 rows. The 1st and 2nd rows should have 9 letters and the 3rd row should have 8 letters.

The numbers on the middle and bottom screen of page 1 is an encrypted word using the key you made.

Treat the middle screen as the rows of each number and the bottom screen as the columns of each number.

For each row/col pair, use the intersection in the key to get a decrypted letter.

You should now have a decrypted keyword that will be used in step 3 so hang on to it.

#### Example

Middle Screen: 232211
Bottom Screen: 236372

HJKLMNOPQ
STUVWXYZ

22 -> J
33 -> U
26 -> N
23 -> K
17 -> E
12 -> R
Decrypted Keyword: JUNKER

### Step 2: Atbash Cipher

Take the encrypted word from the top screen on page 1 and turn each letter into its alphabetic position (A = 1, B = 2... Z = 26).

Next, take 27 minus each number to get a new number between 1 - 26.

Convert each number back into a new letter.

You should now have a new encrypted word.

#### Example

Encrypted Word: IEZCQQ

I -> 27 - 9 = 18 -> R
E -> 27 - 5 = 22 -> V
Z -> 27 - 26 = 1 -> A
C -> 27 - 3 = 24 -> X
Q -> 27 - 17 = 10 -> J
Q -> 27 - 17 = 10 -> J
New Encrypted Word: RVAXJJ

### Step 3: Vigenere Cipher

Using the new encrypted word you got from step 2 and the keyword from step 1, take the first letter of your encrypted word and the first letter of the keyword and turn them into their alphabetic positions.

Now take the first number minus the second number, and then turn the new number back into a letter using its alphabetic position.

If the resulting number is 0 or below, add 26 until the number is between 1 - 26.

Repeat this for each letter to get your decrypted word.

#### Example

Encrypted Word: RVAXJJ Keyword: JUNKER

R, J -> 18 - 10 = 8 -> H
V, U -> 22 - 21 = 1 -> A
A, N -> 1 - 14 = -13 + 26 = 13 -> M
X, K -> 24 - 11 = 13 -> M
J, E -> 10 - 5 = 5 -> E
J, R -> 10 - 18 = -8 + 26 = 18 -> R
Decrypted Word: HAMMER

Once you finally have your decrypted word, you can submit it. Once you start typing, all the screens will go black and the bottom screen will show what you are typing.

To clear it, just click one of the arrows. This goes to one of the pages and clears any input you put in. It will not let you go over 6 letters on input.

Once you are satisfied with your input, press the button labeled "SUB" to submit your answer. On a strike, the module will go back to the first page of the module, but it does not regenerate.