Subject: 
          ps09
    Date: 
          Thu, 18 Jan 2001 13:32:05 -0800
   From: 
          Leonard Schulman 
      To: 
          cs138class@cs.caltech.edu




Comments on two problems:

Problem 1: There is an error because 3 is not a generator mod 1823. But,
5 is. So, compute log_5 693 mod 1823.

Problem 3: Note that the decryption mechanism is only required to
provide decryptions of the specified form (x,r,00000). There was some
confusion about what you are asked to do. You are asked to either prove
the positive claim (decryptions almost always unique + as hard as
factoring), or show why one of these claims breaks down, i.e. either why
decryptions are not almost always unique, or why the proof of hardness
of Rabin's cryptosystem, breaks down for this one.

-- 
Leonard J. Schulman
Associate Professor of Computer Science     Office: 626 395 6839
California Institute of Technology          Fax:    626 792 4257
MC 256-80                                   Scy:    626 395 6842
Pasadena CA 91125                           schulman@cs.caltech.edu
USA                                         www.cs.caltech.edu/~schulman