On the Subject of Unfair’s Revenge

Now it’s more unfair because it took 2 months for him to create only to receive backlash, and another month to make sure he didn’t screw up any more than that.

The display on top shows the encrypted message. There’s also a strip of LEDs underneath the display which will light up to show the current stage the defuser is on.

The display on the right can be clicked to toggle between showing the Module ID, in white, or strikes the module is keeping track of, in red. Both of these are shown in Roman numerals.

For all operations involving STRIKES, always refer to the number in red on the module itself.

The module encrypts a string of four repeatable three-letter-long instructions with four different ciphers, using different keys for each. Enter the correct combination of inputs to disarm the module.

ALL ciphers referring to the alphabetical position refers to the A1Z26 standard for each letter unless stated otherwise.

• The basic order of the given encrypted text is the following: Original -> Playfair Ciphered -> Affine Ciphered -> Caesar Ciphered -> Pigpen Ciphered. Reverse the order to obtain the original instruction string.

Key A

1. Start with the bomb’s first 3 serial number characters.
2. Interpret each character from this set as a base-36 digit.
   • If the character is unfamiliar in the set of base-36 digits, interpret this character as the digit “I”.
3. Convert this base-36 number into decimal. Use Appendix Base-36 Conversion in case for reference. You will need to prepend this to the result of the next step.
4. Grab the bomb’s last 3 serial number characters and transform each letter into its numerical equivalent (A = 1, B = 2, etc.).
   • Make this a single string of digits.
5. Append the result from converting the base-36 value with the modified string from step 4. Interpret this as one number.
6. Convert this number into hexadecimal. Refer to Appendix D3K2H3X for instructions.

7. Now read the string of hexadecimal digits as a string of decimal digits and letters. Going from left to right, for every digit:
   • If the digit is followed by another digit and they form a number in the range 10–26, convert the pair into its alphabetical equivalent.
   • Otherwise, convert the single digit into its alphabetical equivalent, or skip it if it is a zero.

8. Transform the Module ID, the number of port plates and the number of battery holders into their alphabetical equivalents, separately, using step 7 if any of these are 0 or greater than 26.
9. Append these characters together, and then at the end of the result of the previous conversion.
10. This is Key A.

Key B

Obtain Key B from the following table using the month and day of the week of when this module was activated:

		Month
		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Day	Mon	ABDA	FEV	DBHC	AEI	DBIE	PLAY	AFCG	ONE	DEAI	ALPH	EFAB	DECC
	Tue	ABDB	FEW	DBHD	OUY	DBIF	HIDE	AFCH	TWO	DEAA	BETA	EFAC	DECD
	Wed	ABDC	FEX	DBHE	WBC	DBIG	SECR	AFCI	THRE	DEAB	CHAR	EFAD	DECE
	Thu	ABDD	FEY	DBHF	DFG	DBIH	CIPH	AFCA	FOUR	DEAC	DELT	EFAE	DECF
	Fri	ABDE	FEZ	DBHG	HJK	DBII	FAIL	AFCB	FIVE	DEAD	ECHO	EFAF	DED
	Sat	ABDF	FEBG	DBHH	LMN	DBIA	PART	AFCC	SIX	DEAE	FOXT	EFB	DEDA
	Sun	ABDG	FEBH	DBHI	PQR	DBIB	BECO	AFCD	SEVN	DEAF	GOLF	EFBA	DEDB

Key C

Use a Playfair Cipher to encode Key A using Key B as the keyword. This is Key C.

Refer to Appendix PL4YF4112 101 for instructions.

Solving — Step 1: Pigpen Cipher

Convert the symbols on the top screen into letters using the chart below.

Solving — Step 2: Caesar Cipher

Condition	Operation
For every port type	-2
For every port plate	+1
For every consonant in the serial number	+1
For every vowel in the serial number	-2
For every lit indicator	+2
For every unlit indicator	-2
For every battery	-1
No batteries	+10
No ports	×2
31 or more modules	÷2

Calculate an offset used for the Caesar Cipher. Start with 0 and perform all operations in the following table for each matching condition.

Drop any remainders and/or decimals when using the division operation. I.E, if you get -1.5 after division, turn -1.5 into -1 instead.

To decipher the message, shift every letter on the screen forwards by this many letters in the alphabet if the offset is negative, backwards if the offset is positive. Wrap back to the other side of the alphabet if you have to go backwards from A or forwards from Z.

Solving — Step 3: Affine Cipher

Condition	Operation
For each BOB, CAR, or CLR indicator:	+1 if lit, -1 if unlit
For each FRK, FRQ, MSA, or NSA indicator:	+2 if lit, -2 if unlit
For each SIG, SND, or TRN indicator:	+3 if lit, -3 if unlit
For the number of batteries:	+4 for odd, -4 for even
There are port plates with parallel port:	+5 each, -4 if paired with serial port
There are port plates with DVI-D:	-5 each, +4 if paired with Stereo RCA

Calculate an offset used for the Affine Cipher. Start with 0 and perform all operations from the table above in this section for each matching condition. If the offset is negative, make it positive. This will be referred to as X for this step.

For each letter in the plain text:

• The alphabetic position of this letter is multiplied by (2X + 1).
• 26 is subtracted from the product until it falls within the range [1, 26].
• This is the alphabetic position of the encrypted letter.

To decrypt, add 26 to the alphabetical position of the encrypted letter until it is divisible by (2X + 1), then divide it by (2X + 1) to get the alphabetical position of the unencrypted letter.

However if X is a number in relation to 13n + 6, the message is encrypted with Atbash cipher instead. The next section explains how to decrypt/encrypt a message in Atbash.

The table underneath can be used to quickly decrypt each letter for Affine Cipher if needed. X = 0 denotes to the first row in the table and the decrypted letter, X = 1 for the 2nd row for the encrypted letter, X = 2 for the 3rd row, etc.

Affine Encryption Table
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
C	F	I	L	O	R	U	X	A	D	G	J	M	P	S	V	Y	B	E	H	K	N	Q	T	W	Z
E	J	O	T	Y	D	I	N	S	X	C	H	M	R	W	B	G	L	Q	V	A	F	K	P	U	Z
G	N	U	B	I	P	W	D	K	R	Y	F	M	T	A	H	O	V	C	J	Q	X	E	L	S	Z
I	R	A	J	S	B	K	T	C	L	U	D	M	V	E	N	W	F	O	X	G	P	Y	H	Q	Z
K	V	G	R	C	N	Y	J	U	F	Q	B	M	X	I	T	E	P	A	L	W	H	S	D	O	Z
The message to decrypt would result in very ambiguous conditions if using X = 6.
O	D	S	H	W	L	A	P	E	T	I	X	M	B	Q	F	U	J	Y	N	C	R	G	V	K	Z
Q	H	Y	P	G	X	O	F	W	N	E	V	M	D	U	L	C	T	K	B	S	J	A	R	I	Z
S	L	E	X	Q	J	C	V	O	H	A	T	M	F	Y	R	K	D	W	P	I	B	U	N	G	Z
U	P	K	F	A	V	Q	L	G	B	W	R	M	H	C	X	S	N	I	D	Y	T	O	J	E	Z
W	T	Q	N	K	H	E	B	Y	V	S	P	M	J	G	D	A	X	U	R	O	L	I	F	C	Z
Y	X	W	V	U	T	S	R	Q	P	O	N	M	L	K	J	I	H	G	F	E	D	C	B	A	Z

Solving — Step 3A: Atbash Cipher

Do not use this if X from the table provided in Step 3 is not 13n + 6!

Each letter is encrypted to the alphabetical position of (27 - P), where P is the alphabetical position of the unencrypted letter.
To decrypt simply get the alphabetical position of (27 - E), where E is the alphabetical position of the encrypted letter.

Solving — Step 4: Playfair Cipher

Use a Playfair Cipher with Key C as the keyword to decrypt the string you just deciphered.

Refer to Appendix PL4YF4112 101 for instructions.

You now have the original message.

Solving — Step 5: Executing the Instructions

Again, the message consists of 4 instructions. Execute the instructions left to right.

Tap the small screen on the right to toggle between showing the module ID or the number of strikes obtained so far, which is shown in red. Both of these are shown in Fixed Roman Numerals.

Instructions:

‘%’ refers to the modulo (remainder) operation.

Inner Center refers to the white button in the middle.

Outer Center refers to the gray circular frame around the colored buttons.

The colored buttons are always in this order, starting from the NW colored button and going clockwise around Inner Center: Red, Yellow, Green, Cyan, Blue, Magenta.

Refer to Appendix PR1M3 for a list of prime numbers.

• PCR: Press the Red button.
• PCG: Press the Green button.
• PCB: Press the Blue button.
• SCC: Press the Cyan button.
• SCM: Press the Magenta button.
• SCY: Press the Yellow button.
• SUB: Press Outer Center when the seconds digits on the countdown timer match.
• MIT: Press Inner Center when the last digit on the seconds timer is (m + c + s) % 10, with m being the Module ID, c being the number of times a colored (R, G, B, C, M, Y) button has been pressed since the last strike on this module (or since the beginning if there are no strikes) and s being the current stage, starting with 1.

• PRN: Press Inner Center if (Module ID % 20) is a prime number; otherwise press Outer Center.
• CHK: Press Outer Center if (Module ID % 20) is a prime number; otherwise press Inner Center.
• BOB: Press Inner Center.
  • If there are exactly 4 batteries in 2 holders and there is a lit BOB as the only indicator on the bomb, skip the rest of the instructions as the module will disarm itself instead.
• REP or EAT: Repeat the last input, or press Inner Center if this is the first instruction. Ignore timing constraints.
• STR or IKE: Starting from Red, count as many colored buttons clockwise as there are strikes. Press that resulting button. In the case of 0 strikes, press the starting button.
  • For these instructions, refer to the Strike Counter on the small screen of the module itself.
• SIG: Press Inner Center. If this is not the very last instruction and this instruction is able to skip the next instruction, then press the Cyan button and skip the next instruction. Otherwise, only the Inner Center press is needed.
• PVP or NXP: Start from the last colored button you pressed (or the NW button if you have not pressed any yet). Go (counter-clockwise if PVP / clockwise if NXP) until you get to a button that is a primary color (R, G, B), then press that button.
• PVS or NXS: Start from the last colored button you pressed (or the NW button if you have not pressed any yet). Go (counter-clockwise if PVS / clockwise if NXS) until you get to a button that is a secondary color (C, M, Y), then press that button.
• OPP: Press the button that is diametrically opposite to the last button you pressed. If your last button pressed was Outer Center then press Inner Center and vice versa. Otherwise, if this is the first instruction, press Outer Center.

Base 36	DEC	Base 36	DEC
0 - 9	0 - 9	O	24
A	10	P	25
B	11	Q	26
C	12	R	27
D	13	S	28
E	14	T	29
F	15	U	30
G	16	V	31
H	17	W	32
I	18	X	33
J	19	Y	34
K	20	Z	35
L	21	10	36
M	22	11	37
N	23	...	...

Appendix: Base-36 Conversion

The table on the right shows a quick lookup for the base 36 values on the table, in base-10 (DEC). To convert a base-36 number into base-10 (DEC):

1. Start on the first base-36 digit with the current value of 0.
2. Add the base-36 value of the digit you are on.
3. If this is not the last base-36 digit, multiply the current value by 36 and go to the next digit.
4. Repeat steps 2 and 3 until you have went through all of the base-36 digits.
5. You should now have a number in base 10 or in decimal.

DEC	HEX
0–9	0–9
10	A
11	B
12	C
13	D
14	E
15	F
16	10
17	11
26	1A
...	...

Appendix — D3K2H3X

To convert a value from base 10 to hexadecimal:

1. Divide the number by 16. Obtain the remainder and quotient.
2. Convert the remainder into a hexadecimal digit. See the corresponding table for a quick reference.
3. Repeat steps 1 and 2 with the quotient as the new number. Keep repeating until the quotient is zero.
4. Reverse the order of the hexadecimal digits obtained.
5. Remove leading zeros.

Appendix — PR1M3

• A prime number is referred to a number that is only divisible by 1 and itself. 1 is not considered prime even though it is divisible by 1 and itself.
• Prime numbers (to 20): 2, 3, 5, 7, 11, 13, 17, 19

Appendix — PL4YF4112 101

• Create a 5×5 matrix of letters. Start with your keyword and fill the rest with the unused letters of the alphabet. Each letter must occur only once in the matrix, so only add the first occurrence. ‘J’ and ‘I’ are interchangeable.
• In the following text, use the instructions marked (d) when decrypting and those marked (e) when encrypting.
• Split the message into character pairs. If you cannot form a pair, add an ‘X’. If the characters are the same, transform the second character into an ‘X’. For each pair:
  • If the letters appear on the same row of your matrix, replace them with the letters to their immediate left (d)/right (e) respectively, wrapping around to the other side of the row if necessary.
  • If the letters are on the same column of your matrix, replace them with the letters immediately above (d)/below (e), wrapping to the other side of the column if necessary.
  • If the letters are on different rows and columns, replace each of them with the letter on the same row but in the column of the other letter in the original pair.
• Drop any final X’s that don’t make sense and locate any I’s that should be J’s.