On the Subject of the Arithmetic Sequence CM

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

From the ƎNA Cipher module by Kilo Bites.

Create a key using the keyword on screen 1 and the Boolean Expression on screen A. This will be referred to as the Sequence Key.

If there is a number on screen B, take out the letter at that position in the encrypted word. Set aside this letter to be put back in at a later step.

Split the encrypted word into letter pairs and for each pair, do the following:

• Note the movement from the 1st letter in the pair to the 2nd letter in the pair within the Sequence Key. (You can pick either direction.)
• Repeat the movement from the 2nd letter to obtain a letter.
• Then repeat the same movement again from the letter you obtained in the last step.
• Reverse the order of the letter pair you got from the previous steps to get a decrypted letter pair.

After doing the sequence for each pair of encrypted letters, if you took out a letter, insert that letter back into position equal to the number on screen B. You should now have a decrypted word.

Example

Encrypted Word: ASSHFSB
Sequence Key: YACHTSBDEFGIJKLMNOPQRUVWXZ
Screen B: 1

ASSHFSB + 1 → SSHFSB
SS → SS → SS
FH → MU → UM
SB → DE → ED
SSUMED + A + 1 → ASSUMED

Decrypted Word: ASSUMED