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Mohamed G. Gouda						Fall 2006 
CS 395T: Network Protocol Security				Midterm 2
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Time: 75 Minutes						Open Book
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1. (8 points)

Describe an algorithm for computing an optimal dispersal for a certificate
chain set CS where each certificate appears in at most three chains in CS.

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2. (7 points)

The following protocol is intended to allow a process p to authenticate
another process q, where both p and q have the same authentication center
ac and p shares an individual key I.p with ac and q shares an individual
key I.q with ac.

	p  --> q  : n
	q  --> ac : I.q <n, p, SK>
	ac --> p  : I.p <n, q, SK>

In this protocol, n is a fresh nonce generated by p and SK is a session
key generated by q. Give a scenario to show that this protocol is loose.

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