Definition 2 (Virtual directededge). Inadynamicvirtualdigraph
DVD(V, E), virtualedge eAE is anarcfromonedynamicnode u to
another dynamicnode v, where u,vAV. Thereisavirtualedge
from node u to node v if andonlyifnode u has obtainedthe
public keyof v in somekindofauthenticatedmanner.
The virtualdirectededgeisquitedifferentfromthatina
traditional graphinwhichthenodesarestaticandthetopologyof
the graphisnotchangedatall.InDVD,thenodesmaybemoving
and graphtopologymaybechangedatanymoment.Thetradi-
tional edgebetweennodespaircannotbeprospected,butthe
virtual directededgedefinedhereisnotaffectedbythechangein
graph topology.