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Mohamed G. Gouda                                    Network Protocol Security
CS 395T                                             MT1 Solution
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1. 

process p

const  T     : integer,     /round-trip delay between p and q
       r     : integer,     /max. value for the shared key
       sk    : 0..r-1,      /shared key between p and q

var    t     : integer,     /text of current data msg
       nc    : integer,     /nonce of current data msg
       nc'   : integer,     /nonce of next data msg
       c     : integer,     /received ack
       ready : boolean

begin
   ready     -->           ready := false;
                           t     := any;
                           nc'   := NNC;
                           send data(NCR(sk, t|nc|nc')) to q

[] rcv ack(c) from q  -->  if nc' = c  --> ready := true; nc := nc'
                           [] nc' <> c --> nc := c;
                                           send data(NCR(sk, t|nc|nc')) to q
                           fi

[] timeout
   ~ready ^
    T time units have passed without executing any action 
             --> send data(NCR(sk, t|nc|nc')) to q
end


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2.

for every certificate (u, v) do the following to disperse (u, v):
    if there is a node x such that x is the source or destination
       of every chain that has (u,v),
    then add (u,v) to D.x
    else if there are two nodes y and z such that y or z is the 
            source or destination of every chain that has (u,v),
         then add (u,v) to D.y and D.z
         else add (u,v) to every D.x where x is the source of a
	      chain that has (u,v).

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