On the Subject of the Gray Cipher

This cipher might seem gray and bleak and boring. Well, I must say... you’re not wrong.

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 screen shows a 6 digit binary string, the bottom screen shows a number.

Follow the mechanics down below to decrypt your word:

Step 1: Bit Switch Cipher

For this, you will need the encrypted word on the top screen of page 1, and the 6 digit binary string on the middle screen.

First determine the scrambler that will be used by using the first character of the serial number:

0	21453	9	23154	I	24513	R	24531
1	21534	A	25134	J	25413	S	25431
2	31524	B	24153	K	34512	T	34521
3	31452	C	34152	L	35214	U	35421
4	41523	D	35124	M	35412	V	43251
5	41532	E	45123	N	43512	W	43521
6	51234	F	45132	O	45213	X	45231
7	51423	G	54123	P	53412	Y	53421
8	51432	H	54132	Q	54213	Z	54231

Next turn each letter of the encrypted word you have so far into a binary sequence using the table below:

A	00001	H	01000	O	01111	V	10110
B	00010	I	01001	P	10000	W	10111
C	00011	J	01010	Q	10001	X	11000
D	00100	K	01011	R	10010	Y	11001
E	00101	L	01100	S	10011	Z	11010
F	00110	M	01101	T	10100
G	00111	N	01110	U	10101

For each binary sequence, if the binary bit (middle screen) at the letter’s position is a 1, invert the bits. Then run it through the scrambler so that the number in each position turns into that position of that number in the binary.

Example

Scrambler: 35124
Binary: 10011
3rd position of 10011 → 0
5th position of 10011 → 1
1st position of 10011 → 1
2nd position of 10011 → 0
4th position of 10011 → 1
10011 → 01101

Finally turn the binary back into a letter using the same table.

Example

Encrypted Word: HMCDCC
Scrambler Used: 54123
Bottom Screen Binary: 011010

H → 01000 + 0 → 01000 + 54123 → 00010 → B
M → 01101 + 1 → 10010 + 54123 → 01100 → L
C → 00011 + 1 → 11100 + 54123 → 00111 → G
D → 00100 + 0 → 00100 + 54123 → 00001 → A
C → 00011 + 1 → 11100 + 54123 → 00111 → G
C → 00011 + 0 → 00011 + 54123 → 11000 → X
New Encrypted Word: BLGAGX

Step 2: Columnar Transposition

For this, you will need the encrypted word from step 1 and the number on the bottom screen of page 1.

Take the number and underneath it, put 6 dashes so that it fits in the columns of the numbers in reading order.

1	2		1	2	3		1	2	3	4		1	2	3	4	5		1	2	3	4	5	6
-	-		-	-	-		-	-	-	-		-	-	-	-	-		-	-	-	-	-	-
-	-		-	-	-		-	-				-
-	-

In ascending order, take the encrypted word and replace all the dashes under the number with the letters.

Finally, read the letters in reading order to get a new order of letters.

Example

Encrypted Word: BLGAGX
Number: 321

3	2	1
G	G	B
X	A	L

New Encrypted Word: GGBXAL

Step 3: Portax Cipher

For this, you’re going to need the encrypted word you got from step 2 and the 3 letter key on the top screen of page 2.

You will also need this cipher table that consists of 4 rows of letters, divided into 2 subgroups of 2 rows:

ABCDEFGHIJKLM
NOPQRSTUVWXYZNOPQRSTUVWXY
-------------------------
ACEGIKMOQSUWYACEGIKMOQSUW
BDFHJLNPRTVXZBDFHJLNPRTVX

Split the encrypted word in half so you have 2 3 letter strings. Place the 2nd half under the 1st half. Each column is treated like a letter pair reading top to bottom. For each letter pair, do the following:

• Shift the top row so that the letter A aligns with the letter on the 3rd/4th row that is the same letter as the Nth letter of the key.
• Find the 1st letter in the pair in the 1st/2nd row that is within the length of the top row.
• Find the 2nd letter in the pair in the 3rd/4th row that is within the length of the top row.
• If the 2 letters are in the same column, the 1st letter will be replaced with the letter in the 1st/2nd row and the 2nd letter will be replaced with the letter in the 3rd/4th row.
• Otherwise, replace the 1st letter with the letter in the same row as the 1st but in the same column as the 2nd. And replace the 2nd letter with the letter in the same row as the 2nd but in the same column as the 1st.

Read the letters by taking the 1st letter in each letter pair in reading order, then the 2nd letter to get your decrypted word.

Encrypted Word: GGBXAL
Key: JSK

G	G	B
X	A	L

				A	B	C	D	E	F	G	H	I	J	K	L	M
N	O	P	Q	R	S	T	U	V	W	X	Y	Z	N	O	P	Q	R	S	T	U	V	W	X	Y
A	C	E	G	I	K	M	O	Q	S	U	W	Y	A	C	E	G	I	K	M	O	Q	S	U	W
B	D	F	H	J	L	N	P	R	T	V	X	Z	B	D	F	H	J	L	N	P	R	T	V	X

GX→ HV

									A	B	C	D	E	F	G	H	I	J	K	L	M
N	O	P	Q	R	S	T	U	V	W	X	Y	Z	N	O	P	Q	R	S	T	U	V	W	X	Y
A	C	E	G	I	K	M	O	Q	S	U	W	Y	A	C	E	G	I	K	M	O	Q	S	U	W
B	D	F	H	J	L	N	P	R	T	V	X	Z	B	D	F	H	J	L	N	P	R	T	V	X

GA→ EE

					A	B	C	D	E	F	G	H	I	J	K	L	M
N	O	P	Q	R	S	T	U	V	W	X	Y	Z	N	O	P	Q	R	S	T	U	V	W	X	Y
A	C	E	G	I	K	M	O	Q	S	U	W	Y	A	C	E	G	I	K	M	O	Q	S	U	W
B	D	F	H	J	L	N	P	R	T	V	X	Z	B	D	F	H	J	L	N	P	R	T	V	X

BL→ AN

H	E	A
V	E	N

Decrypted Word: HEAVEN

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.