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
1	A	B	C	D	F	G	H	I	J
2	K	M	N	O	P	Q	S	T	V
3	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

	Encrypted word: QMAFQE
1. A1Z26	Q17	M13	A1	F6	Q17	E5
2. 27-#	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	J10	N14	Z26	U21	J10	V22
Decrypted Word: FILLED	F6	I9	L12	L12	E5	D4
Result (after subtraction):	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.

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

Text-field calculator:

Text-field calculator link here.

This idea is demonstrated by player t-chen.

Calculations for Step 2 & 3:

• Step 2: 27 - [17, 13, 1, 6, 17, 5] = [10, 14, 26, 21, 10, 22]
• Step 3: [10, 14, 26, 21, 10, 22] - [6, 9, 12, 12, 5, 4] = [4, 5, 14, 9, 5, 18] = DENIER

Case: Some values are negative

• mod 26: [8, 1, -13, 13, 5, -8] % 26 = [8, 1, 13, 13, 5, 18] = HAMMER
• 0 should be replaced by 26