Radha Poovendran Network Security Lab University of Washington

Transcription

1 A Gaph Theoetic Famewok fo Peventing the Womhole Attack in Wieless Senso Netwoks Radha Poovendan Netwok Secuity Lab Univesity of Washington Womholes Hope fo time tavel Womhole: A space-time distotion that links two points in the Univese via a shote path in distance/duation than the diect path. Can be a poblem in wong hands! 2 Outline The Womhole theat in Wieless Senso Netwoks (WSN) Gaph Theoetic Fomulation Related Wok Ou Appoach: Local boadcast Keys Secuity Analysis Conclusions WSN Deployment Envionment Souce: Destination: Ad hoc mode of communication - Distibuted algoithms based on a coopeative pinciple Exchange of infomation locally Deployment egion may be hostile 3 4 1

2 Womhole Attack Example 1 Senso ange Attacke ecods info in Region B Tunnels it via the womhole link to Region A Replays the info to Region A Clustehead in Region A tigges false alam Sensos Sensos epot thei tempeatue Region A eadings to a clustehead senso Clustehead tigges alam if the majoity of the sensos epots eadings ove th Clustehead Womhole link Region B Attacke 5 Womhole Attack Example 2 s 3 s 4 Routing Tee s 5 Senso Womhole link ange Attacke establishes a womhole link between s 31 and s 3. s 31 and s 3 become neighbos in outing tee Sensos {,, s 3, s 4, s 5, s 7 } oute though the womhole link to each any of {s 30, s 31, s 32, s 33, s 34 }, and vice vesa. The attacke contols/obseves lage amount of data. It can selectively dop packets, affect thoughput, cause oute oscillation. Senso s 3 becomes a sinkhole fo the local taffic to {s 30, s 31, s 32, s 33, s 34 } s 7 s 30 s31 s 32 s 33 s 34 6 Impact of the Womhole Theat WSN Applications Monitoing Access Contol Localization Netwok Potocols Routing Neighbo discovey Womhole Attack Popeties Type: Replay attack The integity and authenticity of the communication is not compomised The success of the attack is independent of the stength of cyptogaphic pimitives. Feshness can be guaanteed by a speedy diect link

3 Outline The Womhole theat in Wieless Senso Netwoks (WSN) Gaph Theoetic Fomulation Related Wok Ou Appoach: Local boadcast Keys Secuity Analysis Conclusions Gaph Repesentation of WSN i j E(): set of Senso undiected edges ange V: set of vetices WSN epesented by a Geometic Gaph G(V, E()) 1, e( i, j) = 0, if i j if i j > The Communication Gaph G(V, E G ) need not be identical to G(V, E()), but, E G E() 9 10 Gaph Intepetation of Womholes Womholes violate the geometic gaph model of WSN Womhole link The Womhole Poblem Given a logical gaph G (V, E G )with womholes Womhole link Senso ange Senso ange Fo a Communication Gaph G (V, E G ) with womholes E G E() Womholes tansfom G(V, E G ) to a Logical Gaph G (V, E G ) 11 Extact fom G the communication gaph G(V, E G )with E G E() 12 3

4 Solving the Womhole Poblem If G(V, E()) can be constucted (e.g. known locations of sensos) then: G ( V, E() ) G' ( V, ) S( G, G') E G ' G( V, EG ) S : GxG' G a tansfomation such as XOR opeation between the connectivity matices of G, G What if G(V, E()) is UNKNOWN? 13 Outline The Womhole theat in Wieless Senso Netwoks (WSN) Gaph Theoetic Fomulation Related Wok Ou Appoach: Local boadcast Keys Secuity Analysis Conclusions 14 Packet Leashes Hu et al. A packet cannot tavel futhe than a pe-defined distance Uncetainty egion Packet Leashes Hu et al. Locations of the nodes ae known Geogaphical Leashes d(, ) δ: synchonization eo : (X 1, Y 1 ) : (X 2, Y 2 ) d max δc c: speed of light d(, ) d max + δc (X 1, Y 1 ) t s Data Timestamp, time sent : Accept packet if: d s1, s2 t ts + δ ( ) ( )c Speed of light Time eceived Synchonization eo

5 Packet Leashes Hu et al. Tempoal Leashes: Locations not known Packet Leashes Hu et al. Packets Leashes can detect (and emove) womholes if: t s t e Data Timestamp, time sent Expiation time : Accept packet if: dmax δc te ts = c Fo t e > t s : d max > δc t t e Time eceived Geogaphical leashes: ( t t + δ )c Senso communication ange Tempoal leashes: t t e s = + s c δ Requies tight synchonization Eg: Fo t e >t s, if δ =0.5msec > 150m Visualization of Womholes Wang Constuct a visual epesentation of the WSN s2 Visualization of Womholes Wang Cental Authoity (CA) collects distance measuements of each senso to its neighbos. Womhole-fee link netwok Womhole between, (font view) Womhole between two nodes (side view) Using Multi Dimensional Scaling (MDS), CA computes the elative position of each senso. Idea: Womholes shink the distance between two points causing wapaound in the visual epesentation

6 Outline The Womhole theat in Wieless Senso Netwoks (WSN) Gaph Theoetic Fomulation Related Wok Ou Appoach: Local boadcast Keys Secuity Analysis Conclusions Ou Appoach : LBK LBK: Local Boadcast Keys Nobody speaks English hee!! Τί λένε οι βάρβαροι 私達は日本語で話すことができる Just me, you neighbo Je suis fancais O football basilian é o mais melho Некоторый русский пожалуйста 21 You need to be in the neighbohood to speak the same language and undestand the message 22 Local Boadcast Keys (LBKs) Ns i Ks i s i Womhole link Each senso uses a key Ks i ONLY KNOWN to its neighbohood Ns i. Boadcast infomation encoded with Ks i, cannot be decypted outside Ns i. s j Ns j Coectness of the LBK Solution Imposing LBKs to the womhole infected logical gaph G (V,E G ), 1, e( i, j) = 0, if j holds Ks i othewise Since j holds Ks i iff j in in the neighbohood of i, 1, e( i, j) = 0, if if i j i j > Geometic gaph model is satisfied

7 Establishment of LBKs (1) A) Static Netwok: Locations of the sensos ae known. Establishment of LBKs (2) B) Locations of the sensos ae unknown, how do sensos discove thei neighbos? (X i, Y i ) Womhole link CA A Cental Authoity (CA) distibutes the LBKs to sensos. 25 Senso ange Neighbo discovey schemes ae vulneable to womholes 26 Secue Neighbo Discovey 1.Pefom distance bounding with neighbos Requies: time measuements with nanosecond accuacy Nanosecond pocessing capable hadwae 2.Pefom Secue Localization (SeRLoc) 3.Use Powe Poximity to infe distance 4.Poposed Appoach: Use special nodes we call GUARDS. 27 LBK Establishment Step 1 Guad ange R FK 1 s Senso ange FK 2 FK 3 FK 4 All nodes ae peloaded with a common key K 0 Each Guad G i boadcasts an encypted factional key E K0 {FK i } FK

8 LBK Establishment Step 1 LBK Establishment Step 2 {i,j,k, }: indexes of the Guads head Evey senso announces the indexes of the factional keys it heas and a theshold th {1,2,4} {1,2,4} {1,3,4} s {2,4,5} th=3 {1,3,4} {2,4,5} {2,3,4,5} {2,3,4,5} Sensos collect all the factional keys they hea. If a senso s i shaes moe than th factional keys with establish paiwise key K s1,si LBK Establishment Step 2 LBK Establishment Step 3 Senso distibutes its LBK via unicast to each neighbo s i, using K s1,si. {1,2,4} th=3 {1,3,4} {2,4,5} LBK {2,3,4,5} K s1,s2 =H(FK 1 FK 2 FK 3 FK 4 } H: Collision Resistant Hash function Each senso holds its own LBK and the LBks of its neighbos

9 LBK Establishment non-neighbos What if a node outside the senso ange shaes sufficient keys with? th=2 s {1,3,4} 4 {1,2,4} {2,4,5} Deciding the Theshold value (1) R: Guad ange, l: distance between sensos (l ) A c : Common aea Guads head to both, R A c l R {2,3,4,5} Theshold must be chosen caefully! What do we mean by this? At least th guads need to lay within A c, l Computed as if all neighbos ae at l= Deciding the Theshold value (2) Pobability of establishing a LBK with nonimmediate neighbos Locally computed Theshold Locally decide fo the theshold value th based on # of guads head GH s. R A c l R The theshold is some function of GH s th = f(gh s ) At least th guads need to lye within A c, l > ρ g =0.03 Senso ange ρ g =0.03 Senso ange

10 Womholes against the FK distibution G G Womhole link 2 3 G 6 Attacke tunnels the tansmissions of the FK via the womhole link and eplays at both ends. Sensos, hea set of guads GH s ={ G 7 }, establish a paiwise key and hence, a LBK If th >3, cannot establish an LBK with any of its neighbos G 7 Detecting womholes duing the FK distibution Guads include thei coodinates with evey tansmission of Factional Keys (FK). Oigin point If senso s heas a FK 2R multiple times it is A 1 s unde a womhole O A 2 attack A c If senso s heas two guads moe than 2R apat, it is unde a Womhole link womhole attack P det ρga ga ga1 ( 1 ) ( 1 ) 2 c ρ c ρ e + e e Womhole Attack Detection P det duing the distibution of factional keys Once attack is detected execute challengeesponse scheme to identify the closest guad 99.48% Conclusions We showed: Any candidate solution eliminates womholes if the communication gaph poduced satisfies the geometic gaph constaints We poposed: A scheme fo eliminating womholes when sensos have unknown location and ae not time synchonized Main idea behind the solution: If boadcasted infomation is encypted at each neighbohood with a diffeent Local Boadcast Key, it cannot be decypted at some othe neighbohood