-------------------------------------------------------------------------------
Mohamed Gouda							CS 386 S
Spring 2008							Quiz#4
-------------------------------------------------------------------------------


G:                    u
                       
                   ^  ^  \
            A(2)  /   |   \ I
                 /    |    \
                /     |A(2) \
               /      |      v 
                 A(2)     A        
             y -----> v <----- z
             |        |       
             | \      |      ^ ^
             |  \I    |A   I/  |
             |   \    |    /   |
             |    \   |   /    |
             |     \  |  /     |
             |      v v /     I|
             |                 |
             |        w        |
             |                 |
             |                 |
              -----------------

What is smallest set C of cert in G such that 

a. If y checks that all cert in G are valid, then y can accept B.z as public
   key of z.

b. If y checks that all cert in G are invalid, then y cannot accept B.z as 
   public key of z (even if all cert not in C are valid)

------------------------------------------------------------------------------

(Solution)

C = {(y,z), (w,z)}