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Cryptography Midterm Presentation 2011
Transcript of Cryptography Midterm Presentation 2011
and Breaking Techniques
in Java Shawn Waldon A Shortcut for Encrypting Vigenere Ciphers Due to the nature of the Vigenere square, the row of the plaintext letter and the column of the keyword letter
will always contain the letter
(plainletter + keyletter) mod 26 Applications of the Shortcut in Decrypting
Vigenere Ciphers The shortcut means that when decrypting, the keyword letter can be subtracted from the ciphertext letter mod 26 to find the plaintext letter.
This avoids a loop to find the right space in the Vigenere Square. This is tedious: Plotting Signatures and Scrawls Creating the line graphs is mainly a challenge because the maximum value being graphed varies
Scaling the graph based on the maximum value being graphed is tricky. And it has to work no matter where the maximum value is: Demo ! Questions? An Alternate Form of Vigenere Cipher The encipher and decipher modes of the program also allow using a Vigenere Autokey Cipher I also added a variation of my own here: an 'autokeyword' cipher, which is like an autokey cipher, but with a variable length keyword. So Which type is most secure? With an autokey cipher, the cryptanalyst only has to try 26 different letters for the key
Friedman and Kasiski made solving a Vigenere keyword cipher easier, and modern computers/graphics make them easy to break.
From the several hours of research I did, I can't tell if anyone has even tried my autokeyword cipher idea, and my inclination is that it is more secure than the other two