## On the Subject of the Inverted Cream Cipher

Only those that are the cream of the crop can solve this cipher.

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 4 pages.

On page 1, the top screen shows a 6 letter encrypted word, the middle and bottom screen displays a digit string.

On page 2, the top, middle, and bottom screen shows a 6 letter word. Same thing with page 3.

On page 4, the top and middle screen shows an encrypted string, the bottom screen displays a 7 digit number.

### Step 1: Grandpré Cipher

Take the keywords from the top, middle, and bottom screens from page 2, then page 3 in that order and write them below each other, forming a 6×6 matrix. Write numbers 1 - 6 along the top and left side of this matrix.

The numbers on the middle and bottom screen of page 1 are an encrypted keyword. Treating each number in the middle screen as the row and each digit in the bottom screen as the column, use the intersection of each number pair in the matrix to get a decrypted keyword. This will be called Keyword A.

#### Example

Middle Screen: 3165
Bottom Screen: 1256

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

31 -> S
12 -> E
65 -> E
56 -> D

Keyword A: SEED

### Step 2: VIC Phone Cipher

Concatenate the top and middle screen of page 4 in that order. Convert each letter into a series of numbers by using this table:

 1ABC 2DEF 3GHI 4JKL 5MNO 6PQR 7ST 8UV 9WX 0YZ

To convert it, find the letter in the table, and replace it with the number above it X times where X is equal to the position that letter is in within the letter group. Do this for each letter to get an encrypted number string.

Take the last 3 numbers on the bottom screen on page 4 and keep repeating the 3-digit sequence until the length of the digit string is equal to the length of the encrypted number string you got from the previous step. This is the key number string.

For each digit of both the encrypted number string and the key number string, subtract the key number from the encrypted number, modulo 10 to get a new encrypted number string.

Create an alphabet key by taking the keywords you wrote down in step 1 and concatenating them in reading order. Remove any duplicate letters while keeping the first occurrences.

Create a straddling checkerboard by creating a table with 3 rows and 10 columns. Label the columns with the numbers 0–9. Cross out all the first-row cells in the columns whose labels are present in the first 4 digits of the bottom screen on page 4. Label the 2nd row of the table with the 1st 2 numbers from the bottom screen on page 4. Label the 3rd row of the table with the 3rd and 4th numbers from the bottom screen on page 4. Fill the remaining 26 cells with the alphabet key in reading order.

Convert the encrypted number string back into letters. If the first digit is any of the 1st 4 digits of the bottom screen on page 4, use a pair of digits, where the first identifies the row and the second the column, to obtain a letter. Otherwise, use the corresponding letter from the 1st row.

The resulting letters form another keyword. This will be called Keyword B.

#### Example

Encrypted Keyword: PXJYU DYUKBW
Bottom Screen: 8054629

PXJYUDYUKBW -> 69940820844119

 6 9 9 4 0 8 2 0 8 4 4 1 1 9 6 2 9 6 2 9 6 2 9 6 2 9 6 2 0 7 0 8 8 9 6 8 9 8 2 2 5 7
0 1 2 3 4 5 6 7 8 9 V E R I F Y P H L G M S Q U N T K B O X C W A D J Z

07 -> U
08 -> N
89 -> T
6 -> I
89 -> T
82 -> L
2 -> E
57 -> D

Keyword B: UNTITLED

### Step 3: Chaocipher

Take Keyword A and remove any duplicate letters while keeping the first occurrences. Take the entire alphabet and remove any letters that are present in Keyword A. If the parities of the number of ports and the number of port plates are the same, place the alphabet at the end of the keyword. Otherwise, place the alphabet at the beginning of the keyword. This is will be called Key A.

Take Keyword B and remove any duplicate letters while keeping the first occurrences. Take the entire alphabet and remove any letters that are present in Keyword B. If the parities of the 3rd and 6th characters of the serial number are different, place the alphabet at the end of the keyword. Otherwise, place the alphabet at the beginning of the keyword. This is will be called Key B.

Write Key A above Key B and place an asterisk above the 14th letter of the keys.

Do the following for each letter of the encrypted word from the top screen on page 1:

• Find the Nth letter in Key A. This will be called Character A.
• Replace it with the letter in Key B. This will be called Character B.
• Shift Key A so that the last letter of the key is Character A. Take out the 3rd letter of Key A and place it back in at the position of the asterisk.
• Shift Key B so that the 1st letter of the key is Character B. Take out the 2nd letter of Key B and place it back in at the position of the asterisk.

#### Example

Encrypted Word: ZYTNEQ

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

Z -> I

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

Y -> N

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

T -> V

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

N -> O

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

E -> K

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

Q -> E

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.