On the Subject of the Trisquare 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. Make sure to replace any Js with Is. Rearrange the key into a 5×5 matrix. This will be called Matrix A.

Create a 2nd and 3rd matrix by doing the same steps to create Matrix A but with the keyword on screen 2 and the Boolean Expression on screen B to create Matrix B and the keyword on screen 3 and the Boolean Expression on screen C to create Matrix C.

Form an backwards L shape pattern with Matrix C being in the bottom right, Matrix A in the bottom left, and Matrix B in the top right.

Split the encrypted word into pairs of letters. If there is an odd amount of letters, leave the last letter as the odd letter.

For each letter pair of the encrypted word and the letters on screen D, do the following:

  • Find the 1st letter of the Nth letter pair in Matrix A.
  • Find the 2nd letter of the Nth letter pair in Matrix B.
  • Find the Nth letter of screen D in Matrix C.
  • Use the intersection of the column in Matrix A and the row in Matrix C to get the 1st letter of the Nth decrypted pair.
  • Use the intersection of the row in Matrix B and the column in Matrix C to get the 2nd letter of the Nth decrypted pair.

Finally, if any of the letters on screen 4 match at the same position as any of the letters of your encrypted word, replace that letter with a J. You should now have an decrypted word.

Example

Encrypted Word: UFHAWPS
Screen 4: MGXXVIT
Matrix A: BDFGIKLNOPQRTUVWXYZSCHEMA
Matrix B: ABCEFGHIKMNPQTUVWXYZLORDS
Matrix C: SPENDABCFGHIKLMOQRTUVWXYZ
Screen D: BTY

ABCEF
GHIKM
NPQTU
VWXYZ
LORDS
BDFGISPEND
KLNOPABCFG
QRTUVHIKLM
WXYZSOQRTU
CHEMAVWXYZ

UF + B → OB
HA + T → XE
WP + Y → CT
OBXECTS + MGXXVIT → OBJECTS
Decrypted Word: OBJECTS