Table 3 Computational costs.

nodes height Level

Group key reconstruction

Exponentiations

Node traversal

Node joining/delete

The number of nodes

Rounds

Msgs sent per node

Total Msgs

Node joining

0

Average = 

Joining  =  O(log )

1

Node leaving

0

Average = 

Delete = O (log )

1

Node joining

1

Joining = O (1)

2

1

Node leaving

1

Delete = O(1)

1

1

Node joining

6 to

i

Joining = O(log )

2

3

Node leaving

3 to

i

Delete = O(log )

1

1