Lecture 17: May 5, 2021

Reading: , §10.2
Due: Lab 2, due May 5, 2021 (Note new due date); Homework 3, due May 10, 2021 (Note new due date)

1. Symmetric Cryptography
   1. Polyalphabetic: Vigenère, f_i(a) = a + k_i mod n
   2. Cryptanalysis: first do index of coincidence to see if it is monoalphabetic or polyalphabetic, then Kasiski method.
   3. Problem: eliminate periodicity of key
   4. 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 = AZPC; is that DOIT or DONT?
2. Product ciphers
   1. DES
   2. AES

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ECS 135, Computer Security Version of May 5, 2021 at 11:32PM

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