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Mohamed G. Gouda						Project
CS 395T: Network Protocol Security				Fall 2006
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(25 points)

In class, we discussed an abstract version of the antireplay window protocol
in IPsec. In this abstract version, each data message, from the source p of a 
security association to the destination q of the security association, is of 
the form data(x, s, m), where x is the message text, s is a nonnegative 
integer sequence number, m is a digest of the message defined as follows: 
		           m = MD.(x|s|sk), 
MD is a well-known message digest function, and sk is a key shared between 
p and q.

Specify a "finer" version of this protocol where each data message from p to q
is of the form data(x, s, m), s is in the range 0..ss-1, and ss is an integer
value that is much larger than the window siz w. In this finer version, when 
the sequence number s wraps around, both p and q update their shared key sk
using the assignment statement sk := MD.(sk).

Keep your finer version of the protocol as simple as possible. Also state 
clearly under what conditons is your protocol correct.

Write the project as if you are writing a short (8-12 page) paper. Thus your
project should have an abstract, an introduction, several sections that
describe the original protocol and the new protocol, one section that
analyzes the correctness of the new protocol, and one concluding remarks
section. Your project should also include some relevant references.

I expect that you organize yourselves into groups of 2-3 individuals each. I 
also expect each group to submit only one project by the last day of classes. 

Good luck.