Summary for Week 2

• Lecture 2: We discussed perfect secrecy and its implication on key size (e.g., a scheme that satisfies perfect secrecy has to have key space larger than the message size). We discussed how puedo-random number generators (PrNGs) can address this problem. We discussed two PrNGs: LCG and LFSRs.
  Reading assignments: chapter 2 from the Stallings book.
  Date: Tu, 09/07/2010.
• Lecture 3:We discussed LFSRs and Geffe generators. We also covered an attack on LFSRs which illustrated how linearity should be avoided in security. We described a modern PrNG (called the Blub-Blum-Shub (BBS) PrNGs).
  Note:Page 206 of "the handbook" describes correlation attack on Geffe generators.
  Reading assignment: Read about stream-cipher RC 4 from Boneh-Shoup
  Date: Th, 09/09/2010.




• "the handbook" refers to Alfred J. Menezes, Paul C. van Oorschot and Scott A. Vanstone, Handbook of Applied Cryptography, CRC Press, 2001. This book can be found online and a link is provided on the class homepage.
• Boneh-Shoup refers to the chapters being handed out in class.
• L. Blum, M. Blum, and M. Shub, A simple unpredictable psuedo-random generator, SIAM Journal of Computing, 15(1986), pages 364--383.