## On the Subject of The Crimson Cipher

Confusion will be my epitaph...

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 are a total of 3 pages.

### Step 1: Transposed Halved Polybius Cipher

This step uses the encrypted word as well as the two keys on page 1; known as the fractionation key and the transposition key respectively.

To begin, take the fractionation key and enter it into the left half of the Halved Polybius Square in reading order, removing duplicates while keeping the first occurrences. Add the rest of the alphabet letter by letter, moving to the right half after running out of letters. The Halved Polybius Square is laid out like the diagram below.

1 | 2 | 3 | 4 | 5 | 1 | 2 | 3 | 4 | 5 | |

1 | ||||||||||

2 | ||||||||||

3 | # | # | # | # | ||||||

L | R |

Convert each letter of the encrypted word into three coordinates and write them out top to bottom in the order Half, Row, Column and to the right of any previous coordinates.

Then, for each letter of the transposition key, find it in the Halved Polybius Square and perform the following operation on the 6×3 matrix of coordinates you created.

- If you are at an odd step in the process, shift the row of that letter’s coordinate in the matrix to the left by the column coordinate.
- When doing this, do not move threes in the second row and fours and fives in the third row.