The Sensors Connectivity within SCADA Automation Environment and New Trends for Security ...

16 Pages·2015·4.3 MB·English

Hindawi Publishing Corporation
International Journal of Distributed Sensor Networks
Volume 2015, Article ID 738687, 15 pages
http://dx.doi.org/10.1155/2015/738687
Research Article
The Sensors Connectivity within SCADA Automation
Environment and New Trends for Security Development during
Multicasting Routing Transmission
AamirShahzad,1KalumPriyanathUdagepola,2Young-keunLee,3
SoojinPark,4andMalreyLee1
1CenterforAdvancedImageandInformationTechnology,SchoolofElectronics&InformationEngineering,
ChonbukNationalUniversity,Ga,Deokjin-Dong,Chonbuk664-14,Jeonju561-756,RepublicofKorea
2DepartmentofInformationandComputingSciences,ScientificResearchDevelopmentInstituteofTechnologyAustralia(SRDITA),
38aHaigRoadLoganlea,Brisbane,QLD4131,Australia
3DepartmentofOrthopedicSurgery,ChonbukNationalUniversityHospital,Ga,Deokjin-Dong,Chonbuk664-14,
Jeonju561-756,RepublicofKorea
4GraduateSchoolofMOT,SogangInstituteofAdvancedTechnology,SogangUniversity,35Baekbeom-ro,Mapo-gu,
Seoul121-742,RepublicofKorea
CorrespondenceshouldbeaddressedtoYoung-keunLee;[email protected];[email protected]
Received16January2015;Accepted15April2015
AcademicEditor:SanaUllah
Copyright©2015AamirShahzadetal.ThisisanopenaccessarticledistributedundertheCreativeCommonsAttributionLicense,
whichpermitsunrestricteduse,distribution,andreproductioninanymedium,providedtheoriginalworkisproperlycited.
This study examined the security of SCADA system and its protocols, more specifically, SCADA/DNP3 protocol security. To
achieve the study goals, a SCADA simulation environment is designed for water pumping process through connectivity of
intelligentsensors,thepayloadisconstructed,andsecurityisdeployedinsideDNP3protocolstackandthenbytesaremulticastto
subcontrollers.
1.Introduction or/andoccurredasunicastingtransmission,meaningthatthe
remaining network nodes are unaware during transmission
Incurrentage,thenetworkbaseSCADA(supervisorycon- [2,3].
trol and data acquisition) systems are performing advance Nowadays,SCADAsystemsareemployingmoderntech-
functionsandprovidealloperationalfacilities,astraditional nologies to fulfill the current requirements of industrial
networks such as LAN/WAN and others [1]. The existing infrastructures. Due to massive changed found in arena of
SCADA systems were connected with limited number of real time systems, the communication has been going to
networks and usually the connectivity between network unsecured and undeliverable to destinations due to several
nodes is one-to-one (or unicasting) transmission [1, 2]. In potentialvulnerabilitiesandattacks[4–11].Tominimizethe
few cases, SCADA system provides broadcasting service, security issues of SCADA communication, several end-to-
suchthatbytesarebroadcasttoeachandeverynodewithin endsecuritydevelopmentshavebeenmadeandcommercial
configured network. The broadcasting facility is limited to softwareisemployed[1,12–17].InSCADAsystems,numbers
controller side. In case of unsolicited message (or response ofcryptographykeysaredistributedamongnodesfollowed
bytes), remote sensor-node is authorized to send or issue by SCADA communication requirements [11, 18–21]; the
an unsolicited request to main controller and upon receiv- desiredmessageisencryptedbeforetransmittingtodestina-
ing master node transmits an acknowledge message back tionanduponreceivingatremotesidedecryptionfunction
to remote node. Overall, transmission is usually granted isrequiredandappliedtoopenthesenderrequestmessage
2 InternationalJournalofDistributedSensorNetworks
[12–15, 22]. Encryption based security approaches are con- inbalancesystem,onlymainnodeisauthorizedtoinitiatethe
sideredasbestapproachestohidethesensitiveinformation communicationwithconnectedsubnodesinSCADAsystem
of SCADA systems against adversaries [14, 17, 22–28]; the [1–3].Thebasicconfigurationandspecificationsarerequired
securityapproachessuchasIPSec,SSL/TLS,andpatternhave whethermaincontrollersendsrequesttosubcontrollerorsub
alsobeendeployedinenhancementofSCADAsecuritybut controllerinitiatesthecommunication,andareconsideredat
thesearenotconsideredasbestduetoprotocoldependencies, application layer of DNP3 protocol [34, 35]. The proposed
whilebeingcomparedwithcryptographybasedapproaches study employs a balance system in SCADA multicasting
[23,29–31]. transmissionanddeploysthesecuritybeforetransmittingof
Inresearchespapers[2,23,25],symmetrickeyencryption bytestoopennetwork(s).
isdeployedwhichmadesecurityenhancementintransmis- The rest of research paper is organized as follows. In
sionofpayloadinSCADAsystemorbetweenSCADAfield Section2, problem statement is conducted that is directly
devices; the field devices are designated as sensor device linkedwithproposedstudy,andresearchobjectivesareiden-
whichareconnectedwithphysicalworldandconfiguredto tified that are considered as building blocks of proposed
manipulate the information from and process to SCADA study. A simulation is designed for water pumping system
main controller [29, 30, 32, 33]. The main controller is in Section3 and its overall control is managed by SCADA/
supervisorial in SCADA hierarchical structure and sensor DNP3 system. The SCADA/DNP3 testbed setup is created
devicesaretreatedasslavedevices;thenetworkstructureof and multicasting sensor-nodes are configured in Section4,
SCADAsystemsaredefinedasstatisticalstructure,meaning while Section5 explains the detail security development
thatallnetworknodesaredefinedandconfiguredinadvance. and its corresponding communication details. Performance
The hierarchical structure is static, so there is minimal assessmentandcomparisonismadeinSection6whichshows
chance of attacks such as man-in-the-middle attack or/and the significant computed results. The existing survey on
network attacks [23]. In other researches [25, 30, 31], the SCADA/DNP3 securityissues isdescribed inSection7and
use of commercial security software in SCADA systems Section8concludestheoverallstudy.
is considered inappropriate due to number of limitations
such that mostly commercial tools designs are based on
2.ProblemStatement
general manipulation of SCADA system security without
concedesofspecifiedSCADAprotocol(s)[16,17].Thehash-
The multicasting transmission between SCADA sensors-
ing algorithm is accounted as a best security approach in
controllers (or nodes) is commonly found and required in
SCADAtransmissionor/andSCADAprotocolstransmission
SCADAsystems.Inparticular,inthecaseofwarmtrafficor
[23, 30]. Hashing algorithm (or SHA-2 hashing algorithm)
abnormal scenario, in which the attacker successfully gains
is deployed during message exchanging of DNP3 protocol
control, distinguish sensors-controllers and other SCADA
as a part of SCADA communication system. The DNP3
sensors-controllersremainedthesameornormallycommu-
payload is generated and hashing function is applied on to
nicate with main controller. The main controller analyzes
compute the hash digest of payload; the hashing function
theabnormalcommunicationwithinnetworksystemandis
produced a fixed value of payload that would be helpful to
protect the payload from integrity attacks such as payload unabletorecoverthem,asnormalcommunication,andalso
modification and payload reply. The original payload and has no alternative solution for system recovery. Therefore,
computed hash digest is transmitted to outstation (i.e., a main controller gives the alarm to all stations to turn off.
sensingdeviceoracomputerconnectedwithsensor).Upon In this scenario, whole SCADA transmission is suffered
receiving, hash digest is again computed by outstation to including normal sensors-controllers, which significantly
make comparison with main controller hash digest; on the affects the critical communication or SCADA system com-
basis on comparison result the decision would be made munication. The overall transmission is down until system
eitherrejectedoraccepted.Inconsequenceofcomparison,if recovery, which is the most dangerous situation for critical
maincontrollerandoutstationhashvaluesarematchedthen infrastructuressuchaselectricalstations,waterpumpingand
payloadisacceptedorotherwiserejected,andcorresponding controllingstations,aircraftcontrollingsystems, andothers
conformationisreplied[25,30]. [2,3].
Usually, SCADA system provides two types of com-
municationfacilities:balanceandunbalance,dependingon Research Objectives. The research objective of this study is
protocol uses [2, 3]. Distributed network protocol (DNP3) twofold:
is the most popular protocol, which has been employed
by SCADA systems. DNP3 protocol has four layers in its (i)The SCADA communication is persuaded to multi-
stackincludingapplicationlayer,pseudotransportlayer,data casting communication, and its security directions
link layer, and physical layer. In each layer, message size willbehelpfultohandletheabnormalscenarios.
is limited up to 2048 bytes, 250 bytes, and 292 bytes,
and physical layer is helpful during transmission of bytes. (ii)Based on best performance evaluation, the DNP3
The DNP3 protocol is supported for both balance and protocol stack is designed and security solution via
unbalance communications, decided at its data link layer. cryptographyisdeployed,withSCADA/DNP3trans-
Meaning that, in unbalanced system, each and every node missionacquirementsinmindduringbytesmulticas-
isabletoinitiatethecommunicationwithmainnode,while, ting.
InternationalJournalofDistributedSensorNetworks 3
Heat control
sensor
Cold control
Main controller sensor
Pressure
sensor
Pressure
Subcontroller
sensor
Local storage Subcontroller In security Local storage Cooler
Heater
Motor
Motor
Main storage
Cool water storage
Hot water
storage
Figure1:SCADA/DNP3supervisoryenvironment:waterpumpingsystem.
3.SCADASimulationEnvironment 4.SCADATestbedSetupandConfiguration
SCADAsimulationenvironmentisdesignedforwaterpump- InSCADAtestbed(inFigure2),sixremotestations(orsub-
ing system which collects the water from external source controllers), plus sensor- controller node (or RTU1) which
and performs the operations of cooling and heating, which istreatedasrendezvouspoint(RP),areconfiguredwithmain
would further utilize industrial processes. In simulation controller. Three subcontrollers such as RTU2, RTU3, and
environment(inFigure1),SCADAmaincontrollermonitors RTU7areindividuallyconnectedtosuperviseandcontrolthe
the whole water pumping system through configured sub- waterheatingprocessesincludingwaterincoming/outgoing
controllers.Rawwateriscollectedinmainstorage(ormain pressure,waterlevel,coolinglevel,andelectricityconsump-
water storage) and distributed to local storages by mean of tion, while the remaining subcontrollers such as RTU4,
motors, which would further use in cooling/heating oper- RTU5,andRTU6areconnectedwithwatercoolingprocesses
ations. Two water pressure intelligent-sensors are directly andperformseveraloperationsincludingmonitorthewater
connected with local water storages, which check/monitor levelinlocalstoragethroughlevelsensorsandwaterpressure
the water pressure status; integrated programmable logic bypressuresensors,coolingprocessesthroughcoolerdevice
controllers (PLCs) are used to manage (or control) the and cooling level by cooling control sensor, and electricity
pumping according to main controller set points. Meaning consumption. On the other side, the overall multicasting
that, if the water level in low in the local storage, then transmission is controlled by node called sensor-controller
operationalheater/cooler(orheater/coolerdevices)isturned nodeandthemaincontrollerisusedforcommandsexecution
off and subcontrollers activate the water pumping from or set points to subcontrollers and monitoring purposes.
main storage. An intelligent-sensor designated as cooling In this study, a simulation base water pumping system is
controlsensorisdirectlyattachedwithcooler(device),which designedinthefirstphase,and,inthesecondphase,security
controls and monitors the cooling levels according to the is implemented during bytes multicasting transmission and
maincontroller/subcontrollersetpoints. itsevaluationprocessthroughattacksscenarios.
Ontheotherside,ifthesensorssensethewaterlevelis
high or according to the set points, then water pumping 4.1. Multicasting Routing. In SCADA/DNP3 testbed, bytes
isdeactivatedandcorrespondingoperationsareperformed. or frames are constructed in DNP3 protocol stack and
Anintelligent-sensorcalledheatingcontrolsensorisdirectly transmittedtointernetprotocol(IP)viauserdatagrampro-
attached with heater (device), which controls and monitors tocol (UDP) which is situated below then DNP3 protocol;
the heating levels according to the main controller/subcon- transportcontrolprotocol(TCP)isusedincaseofresponse
troller set points. The overall information is processed by bytes. In testbed setup (in Figure2), seven subcontrollers
themeansofconfiguredsensors;thesubcontrollersreadthe are configured with main controller or main node via four
informationfromsensors;then,thisinformationisprocessed routers.Theoverallconnectivitybetweensubcontrollersand
tomaincontrollerformonitoringpurposes. main controller is statically configured, meaning that all
4 InternationalJournalofDistributedSensorNetworks
Main controller
R1
Subcontroller
Multicasting group: 224.2.2.2
R2
RTU7 RTU4
RTU2 R3 R4 RTU5
RTU3 RTU6
Figure2:Testbedsetupandconfiguration.
subcontrollers are known in advance, with multicasting Table1:NewDNP3stackwithCDBbytes:theCDBcontained56
groupIP:224.2.2.2whichavoidstheunknownentryduring bytesandwouldbeincreasedaccordingtothebytesrequirements.
multicasting transmission. The routers such as R1, R2, R3, Theadditional32bytesofCRCaredynamicallyaddedinCDBfrom
and R4 are also configured statically, having multicasting datalinklayer.TheCDBhasnumberoffieldswithdistinctbytes,
whichareemployedduringsecuritydevelopment[36].
tables,whilethisshouldbedecidedbymaincontrollereither
deleteoraddthenode(s)from/tomulticastinggroupor/and
Sourceaddress Destinationmulticastingaddresses
multicastingtable.Amulticastingprotocolorprotocolinde-
Userbytes
pendent multicast (PIM) has been used and configured,
Cryptographykeysequence
whichsetsupthedirectionscalleddistributiontreebetween
main controller and subcontrollers of SCADA multicasting Cryptography(bytes):dynamicstorage(bytes)
groupduringtransmissionofbytes,withoutsettingthetime Option(bytes) Padding(dynamicbytes)
tolive(TTL)field.Atotherside,therouter“R1”connected Acknowledgment
with main controller uses the Internet Group Management Noncritical(bytes) Critical(bytes)
Protocol (IGMP) to identify the connected hosts within
Solution:selectmethod
SCADA network and also keeps the track of multicasting
members, based on main controller selection list. Meaning
that,eachtimemaincontrollertransmitsamessagetomul-
ticasting hosts or subcontrollers, the router lookup table is or cryptography dynamic buffer (CDB) is employed which
updatedwithspecifiedsubcontrollerslistviamaincontroller keepstheinformationofsecurityimplementationandother
and the remaining nodes in table are voided by router. All relateddetail.CDBcontains56byteswhichwouldbeutilized
routersareconfiguredstaticallywithspecifiedsubcontrollers, duringwholesecuritydesignandimplementation.InTable1,
buttherouter“R1”connecteddirectlywithmaincontrolleris a field called “user bytes” is designated for those bytes,
updatedeachtimebasedonmaincontrollerselectionprocess which have been constructed in DNP3 stack, while the
for multicasting subcontrollers. When a router receives the otherfieldsincludingsourceaddress,destinationmulticast-
multicasting packets according to main controller selection ingaddresses,cryptographykeysequence,andcryptography
process,therouterforwardsthepacketstosubcontrollersof (bytes),dynamicstorage(bytes),option(bytes),paddingor
multicastinggroup,inconnectednetwork(s). dynamicbytes,acknowledgment,noncritical(bytes),critical
(bytes),andsolutionorselectmethod,belongtoCDB,which
5.SecurityDesignandImplementation performsdistinctfunctionsduringsecuritydevelopment[23,
36].
SCADA/DNP3 stack has been designed and security is InFigure3,eachtimemessagehasbeenmulticastfrom
deployedwithineachlayerincludingapplicationlayer,pseu- main controller to subcontrollers or/and vice versa (in case
dotransportlayer,anddatalinklayer;anewdynamicbuffer ofresponse,acknowledgmentmessage);securityisdeployed
InternationalJournalofDistributedSensorNetworks 5
Secure cryptography solution: encryption process Secure cryptography solution: hashing Secure cryptography solution: encryption process
User application layer: sender (bytes) Application layer: APDU/APDUsbytes (construction) EAHnPacsDrhyU: pA tbiPyoDtne Us( su ebscyirnteegts AkeEyS): Pseudotransport layer: TPDU/TPDUs bytes (construction) Hash: TPDU bytes Data link layer: LPDU/LPDUsbytes (construction) HasELhPn: DcernUycpb rbtyyiytoptenetses (d us eLsciPnrDegt U Ak eEyS): Physical layer: communication media
User application layer: receiver (bytes) Application layer: APDU/APDUsbytes (construction) HDHaeascskhrhey :dy pA)itg:iP eUoDsnstUi sbn: ygcbto yeAmtsEe (psSs ae rcirseotn Pseudotransport layer: TPDU/TPDUs bytes (Construction) HaHsha dshig: eTsPtsD: cUo mbyptaersison Data link layer: LPDU/LPDUsbytes (construction) DHHeaackssrhheyy :pd )et:ini guocebnsrsiy tynbstpge:y ts cteA eodsEm L(SspP eaDcrriUesotn Physical layer: communication media
Secure cryptography solution: decryption process Secure cryptography solution: hashing Secure cryptography solution: decryption process
Figure3:SecurityimplementationwithinDNP3stack:thecurrentstudydeploysacryptographybasedsecuritysolutionagainstSCADA/
DNP3 multicasting in security. Two cryptography algorithms such AES and SHA-2 are employed to compute the security test such as
authentication,confidentiality,andintegrity.Thenonrepudiationtestisalimitationofthisstudy,duetotransmissionlimitations.Thepublic
keycryptographyisnotappropriateforSCADA/DNP3multicastingtransmissionbutshouldbeusedinunicastingcommunication.
before transmitting to open network, such that 3-way- logical stack, with security bytes. The highlighted bytes in
hashing using SHA-2 algorithm is deployed at each layer, DNPstack,thebytes0x00c3and0x00c1,representtheappli-
andsymmetricencryptionusingAESalgorithmisdeployed cation layer header bytes; the byte “0x001c” is representing
in application layer and data link layer of DNP3 protocol. thepseudotransportlayerheaderbyte,andthebytes0x00aa
Meaningthateachsubcontrollerhastwosecretkeysduring and0x00ccarerepresentingthedatalinklayerheaderbytes,
security deployment plus 3-way-hashing. The performance whiletheremaininghighlightedbytessuchas0x001a,0x00ee,
that Figure7 shows is the bytes allocation and utilization 0x002a, and 0x00ee in application layer stack, 0x002a and
during message design and security deployment. The CDB 0x00ee in pseudotransport layer stack, and 0x001a, 0x00ee,
contains 56 bytes, which have been utilized during security 0x002a,and0x00eeindatalinklayerstackarerepresenting
developmentandareenoughforinformationstorage,evenin the security bytes via cryptography dynamic buffer (CDB).
case,maximumbytes,oruserbytesas1992bytesarereceived Thereamingbytesinhexadecimalformatarerepresentingthe
fromuserapplicationlayertolowerlayerofDNP3;without userbyteswhichareconstructedinDNP3stackoreachlayer
use of CRC (cyclic redundancy code) bytes from data link of DNP3 stack and the shaded area shows that the space is
layer.Infewexperiments,secretkeyisonlyemployedondata empty,andthiswouldbefilledupincaseof1992userbytes
linklayerframeorlinkprotocoldataunit(LPDU)bytes,not thatareconstructedandmanipulatedinapplicationlayer.
inapplicationlayer.Thecorrespondingperformanceresults Themessageisdistinguishedatapplicationlayerwhether
are significantly affected, while being compared with first sending bytes or response bytes. In application layer, send-
security deployment scenario. In testbed, link layer frame ing/responsemessageisdistinctbyoccupiedbytes.Meaning
orLPDU bytes are encrypted, but in few cases, this isdiffi- thatsendingheadercontainstwobytesandresponseheader
cult to identify the main controller or/and subcontrollers contains same fields of sending header, plus two bytes field
addresses. Therefore, two external fields, source address, 2- calledinternalindication(IIN).
bytes (unassigned), and destination multicasting address,
4-bytes (unassigned), are added which would be meaning Example. Suppose that main controller wants to execute
full in identification process, and authentication process of read/writecommands,andsubcontroller(s)willresponseby
internal/external addresses during decryption operation, at employingIINfield.Suchthat
data link layer. Table2 shows the detail of CDB field’s and Request:ReadFunction<C301>
correspondingbytesdetail.
In Figure4, SCADA/DNP3 stack is designed and bytes Response:<C3810000>
are flowed from user application layer to DNP3 application Request:WriteFunction<C302>
layeranddownward.TheDNP3stackisdesignedtomanage Response:<C3810000>
themaximumbyteswhichflowfromuserapplicationlayeror
incase,whenapplicationlayerbufferisfullas2048bytesplus Thebyte“C3”isrepresentingtheapplicationcontrol(AC)
56 bytes of CDB. The number of rows (RWs) and columns andfunctioncode(FC)“01”isaddedforread(request)and
(CLs) with corresponding offsets shows the complete DNP functioncode(FC)“02”isaddedforwrite(request).Onthe
6 InternationalJournalofDistributedSensorNetworks
Table2:CDBdynamicfieldswithallocatedbytes.
Number Fieldname Occupiedbytes Description
Externalfieldrepresentingthemaincontrolleraddressduring
1 Sourceaddressandport 2bytes
multicastingtransmissionorincaseofresponsefromeachsubcontroller
Destinationmulticasting
2 4bytes Representingthemulticastingaddressesofselectedsubcontrollers
addressesandports
3 Userbytes 2bytes Keeptheinformationofprotocolconstructedbytes
Cryptographykeysareemployedwithdistinctnumbersandcountedin
4 Cryptographykeysequence 4bytes
thisfield
Cryptography:dynamic Informationisupdatedandbytesaredynamicallyin/out,accordingto
5 22–56bytes
storage therequirements
6 Option 2bytes Verifythecontentsofmessage,beforetransmission
7 Padding 2bytes Ensureandshowthestatusofcompletedmessage
8 Acknowledgment 2bytes Maincontroller/subcontrolleracknowledgmentmessage
9 Critical 1byte Showthestatusofabnormalentity
10 Noncritical 1byte Ensurethebytesareflowedinnormaltransmission
11 Solution:selectmethod 1byte Showthedetailofsecuritymethodthatisbeingused
otherside,internalindication(IIN)fieldcontainstwobytes, Proof (security development). The “𝑋” is application layer
andcorrespondingcodes<0000>aregeneratedinresponse, constructed bytes and “𝜇” is a function that performs
plusfunctioncode(FC)“81”inbothcases:readandwrite. theencryption“Ey”onbytes“𝑋.”Thetotalconstructedbytes
from application layer have been added in cryptography
Request:Cold RestartFunction<C30D> dynamicbuffer(CDB)“𝑏dy”andcryptographyfunctionssuch
Response:<C3810000> as symmetric encryption “Sym𝑓” using AES algorithm and
Request:Warm RestartFunction<C30E> hashing “𝐻𝑓” using SHA-2 is performed on bytes. Upon
receiving,decryptionfunction“Dy”isperformedusingthe
Response:<C4810000> sharedkeyswithsender/receiverhashdigests.
In another example, main controller wants to execute ApplicationLayer.Encryptionprocessisasfollows:
thecold restartandwarm restartfunctionsusingcodes:0D
and0E.Inresponse,subcontrollerstransmitIINcodes<00 {
00>, plus function code (FC) “81” in both cases, but AC ∃:∀𝜇A𝑆(L𝑚,𝐻,𝐸[𝑘]):EyA𝑖←L𝑢 ,𝐸→Sym𝑓,𝐻→𝐻𝑓{∃:∀𝑋A𝛼=L∧
rb {
code is different as “C3,” in case of cold restart and “C4”
incase ofwarm restart. In multicasting,each subcontroller
is responses with distinct sequence number. Application lim←𝑘 } (1)
control (AC) field contains 5 bits subfield called sequence, ⋅ ∑ ∃:∀𝜇A𝑆L(𝑓𝑛 :𝑋𝑓AL→𝑓 )}‖𝑓𝑛 :𝑓𝑛 :
𝑛
plus 1 bit of confirmation. Therefore, each subcontroller is 𝑖←𝑢rb,𝑓→𝑓𝑛 }
responses to main controller using distinct sequence num-
bers,from0to15. 𝑋AL .
𝑏dy,𝑓→𝑓
ThemoreconciseflowofSCADA/DNP3systemisillus- 𝑛
trated as in Figure5. In multicasting flow, DNP3 protocol
bytes are constructed in each layer, and corresponding ApplicationLayer.Decryptionprocessisasfollows:
functionsaremanipulatedfollowedbyrequestandresponse
∃:∀𝜇AL :
messages[25,37].Atmaincontrollerside,DNP3requestis 𝑅(𝑚,𝐻,𝐸[𝑘])
generated and multicast to remote terminal units (RTUs),
followedbymulticastinggroup.Fourremoteterminalunits {
AL AL
(RTUs) included RTU3, RTU4, RTU6, and RTU7 and are Dy𝑖←𝑢 ,𝐷→Sym𝑓,𝐻→𝐻𝑓{Ey𝑖←𝑢 ,𝐸→Sym𝑓,𝐻→𝐻𝑓
depictedwhichreceivedthemaincontrollerrequestmessage. rb { rb
In response bytes flow, response is generated from RTUs (2)
lim←𝑘 }
and transmitted back to main controller; in this scenario,
unicastingcommunicationisemployedratherthanmulticas- ⋅ ∑ ∃:∀𝜇A𝑆L(𝑓𝑛 :𝑋𝑓AL→𝑓 )}‖𝑓𝑛 :𝑓𝑛 :
𝑛
ting. Numbers of examples are taken from SCADA/DNP3 𝑖←𝑢rb,𝑓→𝑓𝑛 }
transmission during flow of request/response bytes and are
𝑋AL .
visualizedasinFigure6. 𝑏dy,𝑓→𝑓𝑛
InternationalJournalofDistributedSensorNetworks 7
DNP3 stack with UDP protocol
Source address: logical port number Multicasting destination addresses
Session
App. offset
(Logical) APDU with encryption bytes
(logical)
0x0000 RW/CL CL0 CL1 CL2 CL3 CL4 CL5 CL6 CL7 CL8 CL9 CL10 CL11 CL12 CL13 CL14 CL15 CL16 ··· CLn
0x0010 RW0 8d 2b 8d af 8d 6c af ca fa 4c fe 1e cf 0d fa fa cf
0x0020 RW1 fa 84 ba a2 fa 6e a2 b8 1e cf 0d ba ea fa a7 ba cf
0x0030 RW2 a2 ca ee 4c a2 aa ee ee 98 0d ee 8d 6c af 1e 8d 34
0x0040 RW3 fa 84 ba a2 fa 4c fe 1e cf 0d fa 84 ba a2 6e a7 ba
0x0050 RW4 fa cc ba 6e fa a7 6e ec 2b ba ea fa aa ca bf ca cf
0x0060 RW5 a2 fa 4c a2 aa c3 01 1a ee 2a ee
0x0070 RW6
0x0080 RW7
0x0090 RW8 xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx
0x0100 RW9 Reserved
Tran. offset
(Logical) TPDU with encryption bytes
(logical)
0x0000 RW/CL CL0 CL1 CL2 CL3 CL4 CL5 CL6 CL7 CL8 CL9 CL10 CL11 CL12 CL13 CL14 CL15 CL16 ··· CLn B)
D
0x0110 RW0 fe ba fe ba ba 1e ba fe ba ba 1e ba 1e ba cf ba cf C
0x0120 RW1 fa a7 4c a7 4c a7 f3 fe fe ba fe ba ba 1e 48 ee 48 er (
ff
u
0x0130 RW2 fe b8 f3 ba fe ba fe 4c ba 1e ba 1e ba cf ba cf ba b
c
0x0140 RW3 cf a7 cf f3 bf a7 cf f3 ba cf ba cf f3 ba fe fe fe mi
a
0x0150 RW4 fe b8 f3 ba fe ba fe cf ba 1e ba 1e ba cf ba cf fe yn
d
0x0160 RW5 f3 bf f3 bf f3 48 ee 1c 2a ee hy
p
0x0170 RW6 gra
o
0x0180 RW7 pt
y
0x0190 RW8 xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx Cr
0x0200 RW9 Reserved
L(iLnokg. oicffasl)et (Logical) LPDU with encryption bytes
0x0000 RW/CL CL0 CL1 CL2 CL3 CL4 CL5 CL6 CL7 CL8 CL9 CL10 CL11 CL12CL13CL14CL15CL16 ··· CLn
0x0210 RW0 cf cf f3 ba f3 cf f3 cf ba f3 cf ba cf ba cf 34 ba
0x0220 RW1 48 f3 cf f3 bf a7 cf f3 ba cf ba ee 48 ee 48 ba ee
0x0230 RW2 ba b8 f3 b2 fe ba fe 4c fe 1e ba 1e ba b8 ba 8d b2
0x0240 RW3 ee aa ee ee 98 0d ee 8d 6c aa ee ee 98 0d 48 ba ee
0x0250 RW4 6e cf f3 ba f3 ee f3 cf ee f3 cf ba ba b2 ba 8d b2
0x0260 RW5 f3 98 ee 8d 6c 8d 6c f3 aa cc 1a ee 2a ee
0x0270 RW6
0x0280 RW7
0x0290 RW8 xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx
0x0300 RW9 Reserved
Physical layer
Multicasting bytes UDP (protocol) IGMP (protocol)
Figure4:LogicalbytesflowinDNP3stack:thebytesareconstructedaccordingtoSCADA/DNP3protocolspecifications,securityisdeployed,
andcorrespondinginformationisupdatedinCDB.Eachlayerstackshowsthemaximumbytesfollowedbynumberofcolumnsandrows.
Theshadedareashowsthatbytesarenotplaced,becauselimitedbytesarereceivedfromuserapplicationlayer.Therefore,emptycellsare
shadedortreatedaspadding,bywhomDNP3protocolensuresthatmessageiscompleted,withsecurityimplementation.However,fewbytes
arereservedwithineachlayerstack,whichwouldbeusedforfuturedevelopments.
8 InternationalJournalofDistributedSensorNetworks
Figure5:SCADA/DNP3communication:bytesflowduringmulticasting.
The “𝑄” is pseudotransport layer constructed bytes and
“𝛼”isafunctionthatperformsthehashingonbytes“𝑄.”The
totalconstructedbytesfrompseudotransportlayerhavebeen TransportLayer.Decryptionprocessisasfollows:
added in cryptography dynamic buffer (CDB) and hashing
lim←𝑘
fruecnecitviionng“s𝐻id𝑓e”,uhsaisnhgvSaHlu-e2iisspcaerlcfourlamteeddaonndbsyetensd“e𝑄r/.r”eAcetitvheer 𝐻(∃: ∀𝑄T𝛼=L∧⋅𝑖←𝑢∑,𝑓→𝑓 ∃: ∀𝛼T𝑆L(𝑓𝑛 :𝑄𝑓TL→𝑓𝑛))‖
rb 𝑛
hash digests are compared which verified the integrity of
bytes.
𝑓𝑛 :𝑓𝑛 :𝑄𝑏TdLy,𝑓→𝑓𝑛 ∈ℎdigest𝑆 =𝐻(∃: ∀𝑄T𝛼=L∧
TransportLayer.Encryptionprocessisasfollows: (4)
lim←𝑘
⋅ ∑ ∃: ∀𝛼𝑅TL(𝑓𝑛 :𝑄𝑓TL→𝑓 ))‖𝑓𝑛 :𝑓𝑛 :
𝑛
lim←𝑘 𝑖←𝑢rb,𝑓→𝑓𝑛
𝐻(∃:∀𝑄T𝛼=L∧⋅𝑖←𝑢rb∑,𝑓→𝑓𝑛∃:∀𝛼T𝑆L(𝑓𝑛 :𝑄𝑓TL→𝑓𝑛))‖𝑓𝑛 : (3) 𝑄𝑏TdLy,𝑓→𝑓𝑛 ∈ℎdigest𝑅, equalhashvalues.
The “𝐽” is data link layer constructed bytes and “𝛽” is
𝑓𝑛 :𝑄𝑏TdLy,𝑓→𝑓𝑛 ∈ℎdigest𝑆. a function that performs the encryption “Ey” on bytes “𝐽.”
InternationalJournalofDistributedSensorNetworks 9
The total constructed bytes from data link layer have been
added in cryptography dynamic buffer (CDB) and cryp-
𝑓
tography functions such as symmetric encryption “Sym ”
using AES algorithm and hashing “𝐻𝑓” using SHA-2 are
performed on bytes. Upon receiving, decryption function
“Dy”isperformedusingthesharedkeyswithsender/receiver
hashdigests.
DataLinkLayer.Encryptionprocessisasfollows:
{
∃:∀𝛽D𝑆(L𝑚,𝐻,𝐸[𝑘]):EyD𝑖←L𝑢 ,𝐸→Sym𝑓,𝐻→𝐻𝑓{∃:∀𝐽D𝛼=L∧
rb {
lim←𝑘 } (5)
⋅ ∑ ∃:∀𝛽D𝑆L(𝑓𝑛 :𝐽A𝑓L→𝑓 )}‖𝑓𝑛 :𝑓𝑛 :
𝑛
𝑖←𝑢 ,𝑓→𝑓 }
rb 𝑛
𝐽DL .
𝑏dy,𝑓→𝑓
𝑛
DataLinkLayer.Decryptionprocessisasfollows:
∃:∀𝛽DL :
𝑅(𝑚,𝐻,𝐸[𝑘])
{
Freiqguuerset/re6s:poSnCsAeDmAes/DsaNgePs3. communication: bytes flow during DyD𝑖←L𝑢rb,𝐷→Sym𝑓,𝐻→𝐻𝑓{{EyD𝑖←L𝑢rb,𝐸→Sym𝑓,𝐻→𝐻𝑓
(6)
lim←𝑘 }
⋅ ∑ ∃:∀𝛽D𝑆L(𝑓𝑛 :𝐽𝑓AL→𝑓 )}‖𝑓𝑛 :𝑓𝑛 :
𝑛
𝑖←𝑢 ,𝑓→𝑓 }
rb 𝑛
𝐽DL .
𝑏dy,𝑓→𝑓
𝑛
2000
1800
1600
1400 6.PerformanceEvaluationandComparison
1200
1000
800 Number of times testbed experiments has been run and 94
600
experimentsareindividuallyselectedtoperformeachsecu-
400
200 rity test. In each of the 94 experiments, 12 experiments are
0
1 7 13 19 25 31 37 43 49 55 61 67 73 employedandspecifiedforacknowledgment,whilerequired
from subcontrollers 2 experiments are used to check the
Application layer bytes Communication: normal transmission errors and flow; 4 experiments are used and
Pseudotransport layer bytes Type: multicasting specified for acknowledgment, while being required from
Data link layer bytes x-axis: number of experiments
main controller; and remaining 76 experiments are used to
CDB bytes y-axis: random bytes
performmeasurements.
Protocol: SCADA/DNP3
The comparison process of computed performance
Figure 7: DNP3 stack with CDB bytes allocation and utilization: resultsareinvolvedintotwobasicphasessuchastotalattacks
the successful experiments are performed 76 times and the level detection percentages (which are based on fully attacks
ofbytesiscomputedfromtotalallocationandutilizationofbytes. detectionpercentageandpartiallyattacksdetectionpercent-
As shown in 𝑦-axis, random bytes are transmitted form master age) and total attacks impact percentage. As visualized in
controllertosubcontroller(s).Thebluecolorlinesshowthebytes
performance Figure14, the total attacks detection is 11% by
utilized during application layer message construction, red lines
additionoffullyandpartiallyattacksdetectionpercentages,
show the pseudotransport layer bytes, and light green lines show
in case of SCADA/DNP3 stack security, and total attacks
thedatalinklayerbytes,whilepurplelinesareCDBbyteswhichare
dynamicallycomputedformprotocolbythemeansofpadding,plus percentageisincreasedupto28%,incaseofSCADA/DNP3
originalCDBbytes. end-to-endsecurity.
10 InternationalJournalofDistributedSensorNetworks
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1 3 5 7 9 111315171921232527293133353739414345474951535557596163656769717375777981838587899193
Normal/abnormal communication Security: DNP3 (with-in)
Authentication attacks Type: multicasting
Confidentiality attacks x-axis: number of experiments
Integrity attacks y-axis: random bytes
Successful communication
Figure8:AttackdetectionagainstSCADA/DNP3stacksecurity:theattacksincludingauthenticationattacks,guessingsharedkey,brute
force,andpasswordguessing,usingbuilt-inattackingtoolssuchascrackingtools,sniffer,dsniff,winsniffer,andpassworddictionary;integrity
attacks:frameinjection,datareplay,anddatadeletion,usingattackingtoolssuchasairpwn,file2air,dinject/reinject,captureandinjection
tools,andjammingandinjectiontools;confidentialityattacks:eavesdropping,keycracking,andman-in-the-middle,usingattackingtools
suchasethereal,ettercap,kismet,aircrack,airsnort,dsniff,andettercap,arelaunched282times,94experimentsareselected(orsampled)to
verifyeachsecuritytestsuchasauthentication,integrity,andconfidentiality,throughthelevelofattacksdetection.Theattackspresentedby
coloredmarkersshowthesuccessfuldetectionofattacks.Thegreenflowedlinesshowthenormaltransmissionduringbytesmulticastfrom
maincontroller,in-between,attacksaredetected,andthenbytesfollowthenormalsequence.On𝑥-axis,94experimentsaresampled(or
collected)fromtotalexperimentswhichshowedthemostapproximateperformances,andsequenceisusedfrom1to94.Total18experiments
arenotlabeledbecausetheseexperimentsareusedforspecialpurposes.
120
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100 RTU3 RTU4 RTU6 RTU7
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1 3 5 7 9 111315171921232527293133353739414345474951535557596163656769717375777981838587899193
Normal/abnormal communication Security: DNP3 (with-in)
Authentication attacks x-axis: number of experiments
Confidentiality attacks Type: multicasting
Integrity attacks y-axis: random bytes
Successful communication Results: partial test
Figure 9: Attack detection (partially) against SCADA/DNP3 stack security: these are attacks, which are detected during abnormal
communicationbuttheinfluenceisminimalor,inotherwords,fewbytesareinterceptedinwholepacket.Theattacksarecountedsowe
designatetheseattacksaspartiallydetectedattacks.Thenumberofexperimentslabeledon𝑥-axisisthesameasFigure8experiments,with
thesamedataratesbutdistinctattacklocations.Thepartiallydetectedattacksareseparatelygraphedwhichshowthedifferencewithfully
detectedattacks(inFigure8).