This is a screencast showing how to use Sage to work with two classical ciphers, the Bifid cipher and the Vigenère cipher.

The Bifid cipher [1] was invented around 1900 by Felix Delastelle. According to Helen Gaines' book ``Cryptanalysis'', this type of cipher was used in the field by the German Army during World War I.

The Vigenère cipher [2] is named after Blaise de Vigenère, a sixteenth century diplomat and cryptographer, by a historical accident. (Vigenère actually invented a different and more complicated cipher.) The so-called ``Vigenere cipher '' cipher was actually invented by Giovan Batista Belaso in 1553. The Confederacy used the Vigenère cipher during the American Civil War.

References:
[1] en.wikipedia.org/wiki/Bifid_cipher
[2] en.wikipedia.org/wiki/Vigenere_cipher


You can download Sage from sagemath.org/. It is a cross-platform free, open-source mathematics software program similar to the (expensive commercial programs) Mathematica, Maple or Matlab.

You can download the Sage notebook worksheet for this screencast from boxen.math.washington.edu/home/wdj/teaching/crypto-sage/

This screen-cast and the sws worksheet are both licensed under the Creative Commons 3.0 BY-SA license.
creativecommons.org/licenses/by-sa/3.0/

Screencast and editing done by me.

Feel free to re-use and redistribute.