Outline for October 3, 2022

Reading: text, §10.1–10.2
Due: Homework 1, due October 5; Project selection, due Oct 7

  1. Cryptography
    1. Codes vs. ciphers
    2. Attacks: ciphertext only, known plaintext, chosen plaintext
    3. Types: substitution, transposition

  2. Symmetric Cryptography
    1. Monoalphabetic (simple substitution): f(a) = a + k mod n
    2. Example: Caesar (shift) cipher with k = 3, RENAISSANCEUHQDLVVDQFH
    3. Polyalphabetic: Vigenère, fi(a) = a + ki mod n
    4. Cryptanalysis: use index of coincidence to see if it is monoalphabetic or polyalphabetic; Kasiski method.
    5. Problem: eliminate periodicity of key
    6. Perfect secrecy: when the probability of computing the plaintext message is the same whether or not you have the ciphertext; only cipher with perfect secrecy: one-time pads; C = AZPR; is that DOIT or DONT?

UC Davis sigil
Matt Bishop
Office: 2209 Watershed Sciences
Phone: +1 (530) 752-8060
Email: mabishop@ucdavis.edu
ECS 235A, Computer and Information Security
Version of October 4, 2022 at 4:19PM

You can also obtain a PDF version of this.

Valid HTML 4.01 Transitional Built with BBEdit Built on a Macintosh