This paper surveys some interesting papers on adding authentication
contributory group key agreement.  Although you seem to have read the
papers carefully and understood them, in general, this paper is
actually more condensed than in the original sources, and thus offers
little help to the reader as a tutorial.

Technical
---------

From a tutorial perspective, there are several places where you could
explain the details more clearly:
 Section 2.1
 - spell out clearly why every member computes the same key and what
   its value is (in terms of r_i values)
 - indicate the range of i in each step.  Clarify that the arithmetic
   in the indices is also modulo n
 Section 2.2
 - make it clear that each message contains i components.  Use
   examples. Show how the group key is calculated.
 Section 2.4
 - indicate the ranges of i in each step.  Clarify that the arithmetic
 in the indices is also modulo n.  In step 2, the range should be till n-1
   
Section 2.4
- why does step 1 involve a broadcast? it is enough for m_i to
  communicate with m_i-1 and m_i+1
- how do the members figure out k_n?  

Section 3
- What about the practicality of this protocol?

There was also a password-authenticated group key agreement protocol
presented earlier in the seminar.  How does it compare?
http://www.tcs.hut.fi/Studies/T-79.7001/2006AUT/esas06_valkonen.pdf 
  
Editorial
---------
Section 2.2
- s/maquerade/masquerade/
Section 2.3.1
- s/r^2/r_2/
Section 3
- s/Quisuater/Quisquater/
References
- Expand refs 4, 6, 7, 10.  The references should be detailed enough
  to let the reader find the sources.  Not enough to rely on google!