Lecture 13 Outline

Reading: §10.2–10.2.4, F
Due: Homework 3, due on May 9, 2018 at 11:59pm; Lab 2, due on May 7, 2018 at 11:59pm

1. Symmetric Cryptography
   1. Polyalphabetic: Vigenère, f_i(a) = a + k_i
   2. Cryptanalysis: first do index of coincidence to see if it is monoalphabetic or polyalphabetic, then Kasiski method.
   3. Problem: eliminate periodicity of key
2. Long key generation
   1. Autokey cipher: key is keyword followed by plaintext or cipher text
   2. Running-key cipher: key is simply text; wedge is that (plaintext, key) letter pairs are not random (T/T, H/H, E/E, T/S, R/E, A/O, S/N, etc.)
   3. 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?
3. Product ciphers: DES

Matt Bishop Office: 2209 Watershed Sciences Phone: +1 (530) 752-8060 Email: mabishop@ucdavis.edu

ECS 153, Computer Security Version of April 29, 2018 at 11:45PM

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