10 http://inventwithpython.com/hacking
Email questions to the author: [email protected]
A Different Cipher Tool: The St. Cyr Slide
Figure 1-11. Photocopy
these strips to make a St.
Cyr Slide.There’s another paper tool that can be used to do encryption and
decryption, called the St. Cyr slide. It’s like the cipher wheel
except in a straight line.Photocopy the image of the St. Cyr slide on the following page (or
print it out from http://invpy.com/stcyrslide) and cut out the three
strips.Tape the two alphabet strips together, with the black box A next to
the white box Z on the other strip. Cut out the slits on either side of
the main slide box so that the taped-together strip can feed through
it. It should look like this:Figure 1-12. The completed St. Cyr Slide
When the black box A is underneath the letter H (and the number
7), then to encrypt you must find where the plaintext letter is on
the long strip, and replace it with the letter above it. To decrypt,
find the ciphertext letter on the top row of letters and replace it
with the letter on the long strip below it.The two slits on the larger box will hide any extra letters so that
you only see one of each letter on the slide for any key.The benefit of the St. Cyr slide is that it might be easier to find the
letters you are looking for, since they are all in a straight line and
will never be upside down like they sometimes are on the cipher
wheel.A virtual and printable St. Cyr slide can be found at
http://invpy.com/stcyrslide.