On the Subject of the Digrafid CM

A machine that knows no bounds when it comes to ciphers.

Create a key using the keyword on screen 1 and the Boolean Expression on screen A. Place a # at the end of the key. This will be called Key A.

Create a 2nd key by doing the same steps to create Key A but with the keyword on screen 2 and the Boolean Expression on screen B. This will be called Key B.

Swap the character shown on screen 3 with the #, using the left character for Key A, and the right character for Key B.

Create a matrix by placing Key A above a string of Arabic numerals going from 1–9 and put another string of Arabic numerals going from 1–9 on the side in reading order forming a 3×3 square. Then take Key B and put it below the string of numbers where Key A is, then put a string of Arabic numerals going from 1–9 on the side going top to bottom, left to right forming a 3×3 square.

Append the character on screen C to the encrypted word. Split the encrypted word into letter pairs. Depending on which instruction is required, apply it to each pair of letters.

If the Submit Button is white, follow the instructions under Encrypt Instructions. Otherwise follow the instructions under Decrypt Instructions.

Encrypt Instructions

• 1: Take the Nth letter pair and find the 1st letter in Key A and the 2nd Letter in Key B.
• 2: Create a 3 digit number by using the letters in the Keys: Column of Key A, Rows of Key A and Key B where one number is present for both, and Column of Key B.
• 3: Write this number top to bottom, to the right of any previous numbers.
• 4: Repeat steps 1 - 3 for each letter pair to get a series of numbers. Read the digit string in reading order to obtain X 3-digit sequences. X is equal to the encrypted word's length, divided by 2.
• 5: Take the Nth 3-digit sequence and use it to get a Nth decrypted letter pair: 1st number as column and 2nd number as row for Key A, 2nd number as row and 3rd number as column for Key B.
• 6: Repeat step 5 for each 3-digit sequence to get your decrypted word.

Decrypt Instructions

• 1: Take the Nth letter pair and find the 1st letter in Key A and the 2nd Letter in Key B.
• 2: Create a 3 digit number by using the letters in the Keys: Column of Key A, Rows of Key A and Key B where one number is present for both, and Column of Key B.
• 3: Append this number to any previous digits.
• 4: Repeat steps 1 - 3 for each letter pair to get a series of numbers. Rearrange the digit string into 3 rows of X columns. Read the digit string in top to bottom, left to right order to obtain X 3-digit sequences. X is equal to the encrypted word's length, divided by 2.
• 5: Take the Nth 3-digit sequence and use it to get a Nth decrypted letter pair: 1st number as column and 2nd number as row for Key A, 2nd number as row and 3rd number as column for Key B.
• 6: Repeat step 5 for each 3-digit sequence to get your decrypted word.

If you appended a character to the encrypted word, there should be exactly 1 # in the resulting characters. Remove this # as this was used to make the length of the encrypted word divisible by 2.

The resulting letters should form a decrypted word.

Example 1

Encrypted Word: AIYYUJSE
Key A: BCFGHIJK#OQRSTUVWXYZPLANEDM
Key B: CEFGHIJKLMOPQRUVWXZST#NDBYA
Screen C:
Using Encrypt Rules

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

AI → 576
YY → 198
UJ → 647
SE → 442

5164
7944
6872

516 → HI
479 → LL
446 → SI
872 → DE

Decrypted Word: HILLSIDE

Example 2

Encrypted Word: PYRRQXZ
Key A: ABCFGIJKLMOPQRS#WXYZHUNTEDV
Key B: #AMGINBCEFHJKLOPQRSTUVWXYZD
Screen C: Y
Using Decrypt Rules

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

PY → 367
RR → 559
QX → 466
ZY → 297

3675
5946
6297

356 → PO
692 → TT
749 → #E
567 → RY

Decrypted Word: POTT#ERY → POTTERY