Midterm Project - The Trithemius Cipher Spring 2017 This project should consist of a short written report which includes your responses for the questions and exercises below. Include a bibliography of sources you used. 1. Who was Johannes Trithemius and when did he live? Was his cipher created before or after the Alberti Cipher? Was it a monoalphabetic or polyalphabetic cipher? Why? Why is it important? 2. Describe how the Trithemius cipher was used. Compare it to the Alberti cipher. Explain what a \progressive key cipher" is. Write out a tabula recta and explain how it was used in the encoding process. How is it different from the Vigenere cipher? 3. Now encrypt the message Cryptography is fun using the Trithemius cipher where you start with the first column of the tabula recta. Do not encrypt spaces. Explain your steps. What key, if any, does the receiver need to decrypt the message? 4. Now decrypt the message JPJDRSKZBASETRAXKJ using the Trithemius cipher where it was encrypted by starting with the first column of the tabula recta. Explain your steps. 5. This cipher is not very secure. One option to improve it, would be start with a column other than the first in the tabula recta. This would be the key that the decoder needs. (a) Encrypt the message Cryptography is fun using the Trithemius cipher and a key of 20 (the starting column number). (b) Now decrypt the message SUSMB where it was encrypted by starting with a random column. Explain your reasoning to decrypt it. How does the decryption process compare with a shifted Caesar cipher? Is it more secure? Why? 6. Another approach to making this more secure is to basically have two (or more) alphabets which are indicated by the starting column; e.g., 10 and 20 or the starting letters \J' and \T". The first letter of the message (assume it is HELP) is encrypted in the usual manner using alphabet 1; for example if we start with the column where\J" is at the top we encrypt \H" as \Q". The second letter of the message is \E" and we use the second alphabet, i.e., we look at the column with \T" at the top and see that we encrypt \E" as \X". To encrypt the \L" we return to the first alphabet which started at column 10 and so now we progress to column 11 and see that it is encrypted as \V'. Lastly we encrypt \P" using the second alphabet so we use column 21 to get \J". Of course we can use more than two alphabets. (a) Encrypt the message \Cryptography is fun" using a key of columns 5 and 12. (b) Encrypt the message \Cryptography is fun" using a key word (which indicates the column numbers) \FSU". 1.