## On the Subject of the AES CM

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

Write the 5 hexadecimal characters on screen 1 top to bottom. Then write the 5 hexadecimal characters on screen 2 to the right of the previous characters, top to bottom. This will be referred to as the Round Key.

For each letter of the encrypted word, do the following:

- Copy each hexadecimal character from the Round Key in reading order and turn the copies into binary to get 5 rows of 8 bit binary sequences.
- Take the Nth letter’s alphabetic position, minus 1 (A0Z25) and convert it into a 5 bit binary sequence and place each bit at the end of each row with the most significant bit written at the top row.
- For each row of the binary sequence: If the amount of 1s is odd, the resulting bit is a 1. Otherwise, the resulting bit is a 0.
- If the Nth bit on screen 3 is a 1, invert the resulting bits.
- Turn the resulting binary sequence back into a letter (A0Z25) to get your Nth decrypted letter. You can get rid of the binary sequence.
- Create a new Round Key by taking the top hexadecimal pair and putting it at the bottom.
- Take the new top pair of the Round Key and use it in the S-BOX Table to get a new top hexadecimal pair.
- For each hexadecimal pair after the top pair, XOR it with the hexadecimal pair above it.
- The resulting hexadecimal pairs become your new Round Key.

### Hexadecimal to Binary

0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
---|---|---|---|---|---|---|---|

0000 | 0001 | 0010 | 0011 | 0100 | 0101 | 0110 | 0111 |

8 | 9 | A | B | C | D | E | F |

1000 | 1001 | 1010 | 1011 | 1100 | 1101 | 1110 | 1111 |