## On the Subject of the Chain Rotation CM

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

The number on screen 1 will be referred to as N.

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

#### Encrypt Instructions

• The last letter of the word is your next obtained letter. Remove it from the word.
• Caesar-shift this letter backward by the alphabetic position of what is now the last letter of the word. (Ignore this instruction if you’ve run out.)
• Prepend this letter to the start of your result so far.
• Cycle your result right by N positions.
• Keep repeating the steps above until you run out of letters.

#### Decrypt Instructions

• Cycle the encrypted word left by N positions.
• Caesar-shift the leftmost letter forward by the alphabetic position of the last obtained letter. (Ignore this instruction if this is the first letter.)
• This is your next obtained letter. Write it down and remove it from the encrypted word.
• Keep repeating the steps above until you run out of letters.

#### Example 1

Encrypted Word: WOTI
N: 4
Using Encrypt Rules

I - T → O
O → O
T - O → E
EO → EO
O - W → R
REO → ORE
WORE → WORE

Decrypted Word: WORE

#### Example 2

Encrypted Word: MFQXSD
N: 4
Using Decrypt Rules

MFQXSD → SDMFQX
S → S
DMFQX → XDMFQ
X + S → Q
DMFQ → DMFQ
D + Q → U
MFQ → FQM
F + U → A
QM → QM
Q + A → R
M + R → E

Decrypted Word: SQUARE

You can use this table as a way to get your decrypted letters. To do so, follow the instructions below:

• Use the keyword’s letter as the row.
• If you are adding, use the encrypted word’s letter as the column. The intersection of the 2 will be your decrypted letter.
• If you are subtracting, find the encrypted word’s letter within the row. The column that the letter is in becomes your decrypted letter.
ABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZA
BCDEFGHIJKLMNOPQRSTUVWXYZAB
CDEFGHIJKLMNOPQRSTUVWXYZABC
DEFGHIJKLMNOPQRSTUVWXYZABCD
EFGHIJKLMNOPQRSTUVWXYZABCDE
FGHIJKLMNOPQRSTUVWXYZABCDEF
GHIJKLMNOPQRSTUVWXYZABCDEFG
HIJKLMNOPQRSTUVWXYZABCDEFGH
IJKLMNOPQRSTUVWXYZABCDEFGHI
JKLMNOPQRSTUVWXYZABCDEFGHIJ
KLMNOPQRSTUVWXYZABCDEFGHIJK
LMNOPQRSTUVWXYZABCDEFGHIJKL
MNOPQRSTUVWXYZABCDEFGHIJKLM
NOPQRSTUVWXYZABCDEFGHIJKLMN
OPQRSTUVWXYZABCDEFGHIJKLMNO
PQRSTUVWXYZABCDEFGHIJKLMNOP
QRSTUVWXYZABCDEFGHIJKLMNOPQ
RSTUVWXYZABCDEFGHIJKLMNOPQR
STUVWXYZABCDEFGHIJKLMNOPQRS
TUVWXYZABCDEFGHIJKLMNOPQRST
UVWXYZABCDEFGHIJKLMNOPQRSTU
VWXYZABCDEFGHIJKLMNOPQRSTUV
WXYZABCDEFGHIJKLMNOPQRSTUVW
XYZABCDEFGHIJKLMNOPQRSTUVWX
YZABCDEFGHIJKLMNOPQRSTUVWXY
ZABCDEFGHIJKLMNOPQRSTUVWXYZ