Summary for Weeks 6 and 7

• Lecture 10: We started extending the indistinguishability game to other kind of adversaries (multiple encryptions and chosen-plaintext attack). We discussed a notion of psuedo-random functions (recall that this discussion was informal).
  Required reading: Chapter 3 (pages 78-80 and 82-87)
  Date:Tu, 10/9/12.
• Lecture 11: Professor Jha was out of town. Kevin Kowalski held a review session.
  Required reading: None.
  Date:Th, 10/11/12.
• Lecture 12: We discussed the connection between psuedo-random functions and block ciphers. Modes of operation enable a block cipher to be used to encrypt/decrypt arbitrary-sized messages. We discussed two modes of operations ECB and CBC. Shortcomings of these modes of operation were discussed.
  Required reading:Chapter 3 (pages 95-97)
  Date:Tu, 10/16/12.
• Lecture 13: We continued our discussion of modes of operation. We discussed two other modes: OFB and CTR. We noted how the CTR mode is "analogous" to a one-time pad. We clarified that a block cipher needs to be a psuedo-random permutation. There was also a quiz this day.
  Required reading: Chapter 3 (pages 97-99).
  Date:Th, 10/18/12.