Screen shots of the Python Encryption Tool

To start the encryption tool, click on the file named "start_encoder_gui" in Windows, or from Dos Shell which is connected to the directory where you've installed the program, type: 

start_encoder_gui.py
(In Windows you may need to type plain "start_encoder_gui"; try both if the first doesnt't work).

XXX Screen shot of start up state. Default encoding mode is "vigenere".


XXX To switch to shift cipher mode, click on "Mode" at the top and select "Shift":


XXX Type a plain text of interest into the plain text line

Type a valid shift key into the key line.


XXX To encrypt a message once you have chosen a key, you use the "C" (for Cipher key). Just click on it and the encryption of the current plain text appears in the Cipher text line.

In this example, I've encoded the plain text "attack at dawn" using the key "shift-4".


XXX If you have chosen a key value that is too large, the encoder will warn you that it has done a conversion when you try to encode,


XXX ... and go ahead and encode:

In this example I've encoded the plain text "Enter plain text here" using the key "shift-27", which is equivalent to "shift-1".



XXX A nice property of many cipher systems is that if know two of the three parameters of the system, you can compute the third. Thus if you know plain text and cipher, you can compute the key. Here we're in a state in which the K line is cleared. Pressing the "K" button ...


XXX ... computes the key.

You can type new plain text into the plain text line, new cipher text into the cipher text line, or a new key into the key line. Once you have cipher and key, you can compute the plain text by pressing "p".

You can clear any of the 3 input lines by clicking on the screw head button to its left.

You can encrypt and verify encryption with the following steps:

  1. Choose a plain text and a key and press "c".
  2. Press the screw head button to the left of the plain text to delete the plain text.
  3. Press the "p" to compute the plain text from the key and cipher text. The original plain text should reappear.


XXX You can also load and save plain text, cipher, and keys using the File Menu at the upper left.