On the Subject of the Porta CM
A machine that knows no bounds when it comes to ciphers.
Do the following instructions:
- Use the Nth letter of the keyword as the row in the table below.
- If the Nth letter of the encrypted word is between A–M, use the letter as the column for the chart. Then the intersection of the row and column of the 2 letters will give you a decrypted letter.
- Otherwise, find the Nth letter of the encrypted word in the same row as the Nth letter of your keyword. The column of that letter will give you a decrypted letter via the A–M row of the chart.
Do this for each letter of the encrypted word and the keyword to get a decrypted word.
If you reach the end of the keyword, treat it as if it wraps around to the beginning of the keyword.
A | B | C | D | E | F | G | H | I | J | K | L | M | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
AB | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
CD | O | P | Q | R | S | T | U | V | W | X | Y | Z | N |
EF | P | Q | R | S | T | U | V | W | X | Y | Z | N | O |
GH | Q | R | S | T | U | V | W | X | Y | Z | N | O | P |
IJ | R | S | T | U | V | W | X | Y | Z | N | O | P | Q |
KL | S | T | U | V | W | X | Y | Z | N | O | P | Q | R |
MN | T | U | V | W | X | Y | Z | N | O | P | Q | R | S |
OP | U | V | W | X | Y | Z | N | O | P | Q | R | S | T |
QR | V | W | X | Y | Z | N | O | P | Q | R | S | T | U |
ST | W | X | Y | Z | N | O | P | Q | R | S | T | U | V |
UV | X | Y | Z | N | O | P | Q | R | S | T | U | V | W |
WX | Y | Z | N | O | P | Q | R | S | T | U | V | W | X |
YZ | Z | N | O | P | Q | R | S | T | U | V | W | X | Y |