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Mohamed G. Gouda                                		CS 386S
Spring 2008                                     		Quiz 6
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Consider an antireplay window protocol where a process p sends a continuous
stream of messages to process q. Each sent message from p to q is of the form

			msg(s, t, h)

where 

s is the (unbounded) sequence number of the message
t is an integer representing the text of the message
h = H(sk, s, t)
H is a secure hash function
sk is a symmetric session key known only to p and q

Assume that the stream of messages received by q satisfies the 100-reorder
condition. 

What is the disadvantage of using a window of size 10 in this protocol?
What is the disadvantage of using a window of size 1000 in this protocol?

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Student Name:
Student EID :
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The disadvantage of using a window of size 10 is that process q may regard a 
received fresh message as replayed and discard it.

The disadvantage of using a window of size 1000 are:
1. The maintained window  has 1000 bits instead of the needed 100 bits.
2. Moving the window to the right takes up to 1000 steps instead of up to 100.