Summary for Week 8

• Lecture 14: We started discussion on block ciphers and discussed Feistel ciphers. We discussed why linear round functions are bad (essentially the adversary uses a known plaintext and a corresponding ciphertext to extract the key using Gaussian elimination to solve a system of linear equations).
  Required reading: Chapter 5 (section 5.2)
  Date:Tu, 10/23/12.
• Lecture 15:We discussed some common linear functions (e.g., swaps, permutation, and "xoring"). We discussed the popular block cipher DES. We also discussed 2DES and the "meet in the middle" attack on 2DES.
  Required reading: Handout provided in class and Chapter 5 (section 5.4)
  Date:Th, 10/25/12.