theadjacentcluster,ifthereisnotraffic,itisconnectedElseittriestoconnecttotheotherpossibilitiesAftertheclusteringofnodesthereisaneedforroutingofmessagesfromsourcenodetodestinationnode.Routingistheprocessofselectingbestpathsinanetwork.Aroutermaycreateormaintainatableoftheavailableroutesandtheirconditionsandusethisinformationalongwithdistanceandcostalgorithmstodeterminethebestrouteforagivenpacket[4].Typically,apacketmaytravelthroughanumberofnetworkpointswithroutersbeforearrivingatitsdestination.RoutingisafunctionassociatedwiththeNetworklayerinthestandardmodelofnetworkprogramming,theOpenSystemsInterconnection(OSI)model.Alayer-3switchperformsroutingfunctions[5].A-STARisanalogoustothesourceroutingofDSR.Inanchor-basedrouting,thesourcenodeincludesintoeachpacketaroutevectorcomposedofalistofanchorsorgeographicpoints,throughwhichpacketsmustpass.Betweenanchors,thegreedyposition-basedroutingisemployed.Inspatialawarerouting,spatialinformationsuchasstreetsmapofacityoradescriptionofhowseveraltownsareconnectedbyhighways,isutilizedtoassistinmaking
routingdecisions.Thespatialinformationrejectstheunderlyingnodedistributionandtopologyofthenetwork.Spatialawareroutingisusuallyusedinconjunctionwithanchor-basedrouting,suchasinTRRandGSRwhereanchoredpathsarecomputedusingthespatialinformation.
A-starachievesbetterperformance(withrespecttotime)byusingheuristics.A-starsearchalgorithmisawidelyusedgraphicsearchingalgorithm.Itisalsoahighlyefficientheuristicalgorithmusedinfindingavariableorlowcostpath.Itisconsideredasoneofthebestintelligentsearchalgorithmsthatcombinesthemeritsofbothdepth-firstsearchalgorithmandbreadth-firstalgorithm.
Thoughroutingandclusteringarereallyimportantstepsforsendingmessagesbutsecurityofthemessagesisequallyimportant.Toincreasethesecurityofthesystem,Time-stampisthemainfactortobeconsideredandisachievedusingTime-Lapsecryptography.InTime-LapseCryptography,receivercandecryptthemessageonlyataparticulartimeevenifitisundesirabletothesender.AtgiventimeTtheServicepublishesapublickeysothatanyonecanuseit,evenanonymously.Sendersencrypttheirmessageswiththispublickeywhoseprivatekeyisnotknowntoanyone–notevenatrustedthirdparty–untilapredefinedandspecificfuturetimeT+δ.[3]
III.SECURITYREQUIREMENTSINWSN’s
AWSNisaspecialtypeofnetworkwhichhasbothsomecommonalitiesanduniquenesswithatypicalcomputernetwork.ThesecurityservicesinaWSNshouldprotecttheinformationcommunicatedoverthenetworkandtheresourcesfromattacksandmisbehaviorofnodes[8]
Dataconfidentiality:Thesecuritymechanismshouldensurethatthemessagetobetransmittedinthenetworkisnotunderstoodbyanyoneexceptintendedrecipient.
Dataintegrity:Themechanismshouldensurethatthereisnoalterationofthemessagealongitspath
Availability:ThisrequirementsensuresthattheservicesofaWSNshouldbeavailablealwayseveninpresenceofaninternalorexternalattacks
Datafreshness:ItimpliesthefreshnessofdatawhentheWSNnodesuseshared-keysformessagecommunication,whereanattackercanlaunchareplayattack
Self-organization:EachnodeinaWSNshouldbeselforganizingandself-healing
Securelocalization:ItisalwaysmandatorytohavetheaccuratelocationofeachsensornodeinaWSN.
Authentication:Itensuresthatthecommunicatingnodeistheonethatisauthenticated.
IV.DENIALOFSERVICE(DOS)ATTACKS
DoSattackisaneventthatdiminishesorattemptstoreduceanetwork’scapacitytoperformitsexpectedfunction[8].