Summary for Weeks 3 and 4

• Lecture 5: We discussed yet another equivalent definition of perfect secrecy. We covered the indistinguishability game corresponding to perfect secrecy. We covered one-time-pad (Vernam cipher) and proved that it was perfectly secret.
  Required reading: Chapter 2 (pages 33 to 36)
  Date:Tu, 9/18/12.
• Lecture 6: We proved that any perfectly-secret scheme has to have key size greater than or equal to the message size (thus limiting the practicality of an encryption scheme that is perfectly secret). We started discussing principles behind modern cryptographic schemes
  Required reading:
  Date:Th, 09/20/2012. Chapter 2 (pages 36 to 37) and chapter 3 (pages 47 to 53)
• Lecture 7: We started discussing how to relax definitions of security (weakening the adversary model and probability of winning the game). Discussed notions of probabilistic polynomial time algorithms (PPTA) and negligible functions.
  Required reading: Chapter 3 (pages 53 to 57)
  Date:Tu, 09/25/2012.
• Lecture 8: We also started discussing the concept of security proofs by reduction. We discussed the new notion of indistinguishability game and started discussing psuedo-random number generators (PRGS).
  Required reading: Chapter 3 (pages 58 to 64)
  Date:Th, 09/27/2012.