## On the Subject of the Blue Cipher

gonna reword the whole cipher series

Press the arrows to cycle between pages. Do NOT press the number screen, that’s the submit button.

### Step 1: Tridigital Cipher

1. Make a keyword: Start with word at Page 2, Screen 1.
• Remove any duplicate letters from it (keeping each letter’s 1st occurrence).
2. Here’s an alphabet string: `ABCDEFGHIJKLMNOPQRSTUVWXYZ`
• Remove letters that appeared in the keyword.
3. If number of indicators is:
• Even: Concatenate keyword `||` alphabet
• Odd: Concatenate alphabet `||` keyword
4. Form a table: Split your key into rows of length 9, 9, 8.
5. Combine Page 1, Screen 2 and Page 1, Screen 3 to get 6 pairs of coordinates.
• (Screen 2, Screen 3) = (Row, Column)
• Find the corresponding letter in the table.
6. That’s Decrypted Word.

#### Example

Page 2, Screen 1: RULER -> RULE (remove duplicates)
Key: ABCDFGHIJKMNOPQSTVWXYZRULE (case #indicators: odd)

1 2 3 4 5 6 7 8 9 A B C D F G H I J K M N O P Q S T V W X Y Z R U L E

Page 1, Screen 2: 113331
Page 1, Screen 3: 587784
Coordinates: (row,col) = (1,5) (1,8) (3,7) (3,7) (3,8) (1,4)
Decrypted Word: FILLED

### Step 2: Atbash Cipher

1. Encrypted word from Page 1, Screen 1: Convert using A1Z26.
2. Compute `27 - number` to get 6 new numbers.
3. New encrypted word: Convert each number back into a letter.

#### Example

 1. A1Z26 2. `27-#` Encrypted word: QMAFQE Q17 M13 A1 F6 Q17 E5 J10 N14 Z26 U21 J10 V22 New encrypted word: JNZUJV

### Step 3: Vigenere Cipher

1. Convert new encrypted word (Step 2) and decrypted word (Step 1) to A1Z26.
2. Subtract: new encrypted word # - decrypted word #
3. If resulting number < 0, add 26 until the number is between 1 - 26.
4. Convert the numbers back to letters by A1Z26.

#### Example

 New encrypted word: JNZUJV Decrypted Word: FILLED Result (after subtraction): J10 N14 Z26 U21 J10 V22 F6 I9 L12 L12 E5 D4 D4 E5 N14 I9 E5 R18 To submit: DENIER

#### Extra Example:

new encrypted word: RVAXJJ; keyword: JUNKER

• In 3rd position, A1 - N14 = -13, so +26 to get M13.

## Tips & Tricks:

### Submission:

• You may use your keyboard to input.
• To clear input: Click one of the arrows, you’ll return to one of the pages.
• To submit: press the “SUB” button after typing the answer.

### Compact Storage:

Merging step 2 and 3 is possible.

 [1] A1Z26 [2] New encrypted word (step 2): 27 - # [3] Decrypted Word (step 1): FILLED [4] Result (after subtraction [2]-[3]): (page 2, screen 1): QMAFQE Q17 M13 A1 F6 Q17 E5 J10 N14 Z26 U21 J10 V22 New encrypted word: JNZUJV F6 I9 L12 L12 E5 D4 D4 E5 N14 I9 E5 R18 To submit: DENIER