On the Subject of Ed Balls

“Ed Balls”
—Ed Balls, 2011

• This module consists of a framed portrait of British politician Ed Balls and six circular buttons with letters on them.
• If the frame is not blue, you’re looking at a different module.
• The letters are E, D, B, A, L, and S, but they are encoded by an invertible affine cipher.
• To disarm this module, undo the transformation to return the letters to their original form and enter the message “ED BALLS.”
• Pressing an incorrect button will result in a strike and reset your input, but will not cause the buttons to change.

On the Subject of Affine Ciphers

An affine cipher is determined by two variables A and B. Letters are encoded as follows:

1. Convert a letter to its alphabetical position, called x.
2. Compute the value Ax + B, and add or subtract 26 until the result is between 1 and 26.
3. The final number is the alphabetic position of the encoded letter.

When attempting to decrypt an affine cipher, the following fact may help:

Any sequence of equally spaced letters (for example, “E, L, S”) will encode to letters that are also equally spaced, wrapping around from Z to A if necessary.