On the Subject of the Autokey CM
A machine that knows no bounds when it comes to ciphers.
The keyword on screen 1 will be referred to as the Autokey Word.
If the Submit Button is white, follow the instructions under Encrypt Instructions. Otherwise follow the instructions under Decrypt Instructions.
Encrypt Instructions
- Take the sum of the alphabetic positions (A1Z26) of the Nth letter of the encrypted word and the Nth letter of the Autokey Word.
- If the resulting number is above 26, subtract 26 until the number is between 1 - 26.
- Turn the number back into a letter (A1Z26) to get your Nth decrypted letter.
- Write the Nth letter of the encrypted word at the end of the Autokey Word.
- Do this for each letter of the encrypted word to get a decrypted word.
Decrypt Instructions
- Take the alphabetic position (A1Z26) of the Nth letter of the encrypted word and subtract it by the alphabetic position (A1Z26) of the Nth letter of the Autokey Word.
- If the resulting number is below 1, add 26 until the number is between 1 - 26.
- Turn the number back into a letter (A1Z26) to get your Nth decrypted letter.
- Write the Nth letter of the decrypted word at the end of the Autokey Word.
- Do this for each letter of the encrypted word to get a decrypted word.