Outline for April 14, 1997

  1. Greetings and Felicitations
  2. Simple substitution ciphers
    1. Do Caesar cipher
    2. Go through how to break it
    3. Present Vigenère tableau
    4. Discuss breaking it (Kasiski method). Note index of coincidence is probability 2 letters chosen at random from ciphertext are alike
    5. Generalize to very long keys and show running key and autokey
    6. Go through rotor systems (Enigma)
    7. Go through one-time pads
  3. Polygram substitution cipher: Playfair
    1. Key is 5 by 5 grid
    2. If m1, m2 in same row, c1, c2 are to immediate right of m1, m2 respectively
    3. If m1, m2 in same column, c1, c2 are below m1, m2
    4. If m1 = m2, insert null in text
    5. if m1, m2 in different rows and columns, c1, c2 form rectangle with c1 in m1's row and c2 in m2's row
    6. if odd number of characters in message, append null.

Notes by Scott Miller: [Postscript] [Text]
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Send email to cs253@csif.cs.ucdavis.edu.

Department of Computer Science
University of California at Davis
Davis, CA 95616-8562

Page last modified on 4/4/97