Midterm Project - the Alberti Cipher Wheel Spring 2017

Midterm Project - The Alberti Cipher Wheel Spring 2017

This project should consist of a short written report (about 5 pages) which includes your responses for (1)-(4), (6), (7) plus the physical Alberti wheel and video/photos illustrating its use as described in (6). Include a bibliography of sources you used.

The Alberti wheel you will use is illustrated in the ﬁgure below and was used with Latin so certain letters are missing.

1. Who was Leon Battista Alberti and when did he live? Why was it so important at the time? Was it used as a monoalphabetic or polyalphabetic cipher? Why? Could it be used as the other type of cipher? (i.e., if you answer monoalphabetic, then could it be used as a polyalphabetic cipher or vis versa)

2. Describe how the Alberti cipher was used. Describe how a pointer character was used, how a key word was used and how the numbers were used to encrypt a shift.. Explain what constitutes a key for the Alberti cipher. How many diﬀerent starting positions are there? 3. The Alberti cipher disk was made to be used in Latin so certain letters (like “H”) are missing. In this case you have to make a decision on how these are going to be encrypted. For example, “H” is often encrypted as “FF”. I believe there are six of these letters missing on the outer disk. State how you are going to encrypt them. 4. The Alberti cipher contains four numbers (1,2,3,4) on the outer wheel. If you use the “O” to encrypt zero, then we could encrypt a number using base 5 (recall that for binary numbers we used base 2, i.e., 0 and 1.) What is the number 15 (in our decimal system) in base 5 and how would you encrypt it assuming the wheel is set as in the ﬁgure.

5. Make the illustrated Alberti cipher wheel out of cardboard, etc.

1 6. Now encrypt the message Cryptography is fun by starting with “q” on the inner ring set to “S’ on the outer ring, a key word of “NOLES” and encode shifts in the order 3, 1, 2, 4, 1. Do not encrypt spaces. What is the key that the receiver needs (assuming they have the identical Alberti cipher) in order to decrypt the message?

7. Make a short video on your phone or take photos of encrypting & decrypting a message. One person should encrypt and the other decrypt. Choose your message to encrypt, along with your key. Include this in your report. You can email me the video or post it where I can access it.