Authentication Transmission Overhead Between Entities in Mobile Networks

Transcription

1 0 IJCSS Intrnatonal Journal of Computr Scnc and twork Scurty, VO.6 o.b, March 2006 Authntcaton Transmsson Ovrhad Btwn Entts n Mobl tworks Ja afr A-Sararh and Sufan Yousf Faculty of Scnc and Tchnology, Angla Ruskn Unvrsty, UK Abstract Ths papr analyss th authntcaton and ky agrmnt (AKA) protocol for UMTS mobl ntworks, whr a nw authntcaton protocol whch s abl to rduc th ntwork traffc and sgnalng mssag btwn ntts, and consquntly th bottlnck at authntcaton cntr s avodd, ths s achvd by rducng th numbr of mssags btwn mobl and authntcaton cntr, and thn rducng th authntcaton tms and stup tm as wll as mprovng authntcaton ffcncy as shown n numrcal analyss and smulaton rsults. In ths papr w propos dynamc lngth () for an array for authntcaton vctor (AV). Ths rqurd dsgnng nw tchnqu to prdct th numbrs of rcords n AV n ach authntcaton data rqust dpndng on th to arrval rat of authntcaton vnts and rsdnc tm of MS n VR/SGS. Th proposd AKA wth dynamc for AV s compard wth th currnt AKA wth fxd lngth for AV. Kywords: AuC, Authntcaton, UMTS, Authntcaton Vctor. Introducton In ordr to provd scurty srvcs n wrlss ntworks, authntcaton s usd as an ntal procss to authorz a mobl trmnal for communcaton through scrt crdntals [4]. Authntcaton procdur s xcutd whn th MS movs from on rgstraton ara (RA) to anothr on (locaton updat), call orgnaton and call trmnaton. Th MS s contnuously lstnng to th broadcast mssag from VR/SGS to dntfy th locaton ara by usng locaton ara dntty (AI), and th MS comparng th AI whch s rcvd wth th AI stord n th USIM. Whn th AI s dffrnt thn th MS xcut authntcaton procdur. Rcntly [] dscussd rducng authntcaton sgnallng n G mobl ntworks, and proposd an automatc slcton mchansm that dynamcally slcts th lngth () of th array to rduc th ntwork cost []. 2. UMTS AKA Authntcaton Protocol Fgur dscrbs authntcaton procdur n G. Th followng stps dscrb th procdur []:. Whn th MS movs to nw VR/SGS ara thn MS snds (IMSI) authntcaton rqust to VR/SGS (Vstor ocaton Rgstr/Srvng GPRS Support od). 2. VR passs ths authntcaton rqust to HR.. HR Gnrats authntcaton vctors AV(..n) and snds authntcaton data rspons AV(..n) to VR/SGS. 4. VR stors authntcaton vctors. In th th authntcaton and ky agrmnt procdur, VR/SGS slcts th th authntcaton vctor AV(), and snds (RAD (), AUT()) to MS. In th VR on authntcaton vctor s ndd for ach authntcaton nstanc. Ths mans that th sgnalng btwn VR and HR/AuC s not ndd for vry authntcaton vnts.. MS computs th rspons RES f 2 (K, RAD), and CK f (K, Rand), and snds RES to VR/SGS. 6. VR compars th rcvd RES wth XRES. If thy match, thn authntcaton s succssfully compltd. Th transmsson btwn th HR/AuC and VR/SGS s usually xpnsv, f ncrasng th numbr of AVs n thn rducs th numbr of transmssons. But, f s too larg, th AVs wll consum ntwork bandwdth. In th G standard, s fxd at rcords. In our analyss w assum that th lnk btwn VR/SGS s scur whn t s blongng to th sam ntwork and nscur whn t blongs to dffrnt ntworks. Whn th MS movs from on VR/SGS to anothr n th sam ntwork, thn th nw VR/SGS rqusts th unusd AVs from th old VR/SGS. If th unusd AVs has formd 2% from th AV, th old VR/SGS dlts all AVs rlatng to ths MS. But whn unusd AVs formd lss than 2%, th nw VR/SGS rqusts nw ADRs. Whn MS movs to nw VR/SGS that blongs to othr ntworks, thn th nw VR/SGS snds and rcvs authntcaton data rqust and rspons (ADR) mssag to gt nw AV to/from HR/AuC. Th followng procdur procss of authntcaton vnt wth data tm dagram s shown n Fg. 2. Thr ar two countr and j, st th ntal valu for thm s 0. MS gnrats vnts (ocaton updat, Call orgnaton and Call trmnaton). VR/SGS chck th vnt If vnt s ocaton Updat thn Incrmnt th two countr and j by At tm T, j xcut ADR, and UAR j

2 IJCSS Intrnatonal Journal of Computr Scnc and twork Scurty, VO.6 o.b, March 2006 Els f vnt s call orgnator or trmnaton thn If thr AVs avalabl n VR/SGS (.. j than or qual ) Incrmnt countr j by At tm T, j xcut UAR j Els St ntal valu for countr j (.. Incrmnt countr by At tm T, j xcut ADR,and UAR j End f End f lss From abov algorthm, whn th MS movs to nw VR/SGS at tm T + and th last authntcaton vnt occurs at T, ( whr ) thn durng th prod T, - T, thr ar - rcords n VR/SGS that ar unusd, ADRs and ( )* + I UARs ar prformd. MS VR/SGS HE/HR Dstrbuton of Authntcaton Vctor. Authntcaton Data Rqust 2. Authntcaton Data Rspons W valuat th prformanc of G authntcaton protocol. Th valuaton mthodology s drawn from []. Assum that a MS maks a numbr of ADRs whch satsfy a Posson dstrbuton wth man λ. Accordng to th quaton (2) for prod T, thr s (-)* + UARs, thn th probablty that thr ar ADRs to th HR/AuC s ( ) (,, ) ( )* + λ - λt T Θ T () [( ) ]! + Whr Θ (,, T ) s th probablty that thr ar n transmssons btwn th MS and VR/SGS durng th prod T. t th MS rsds for a prod t n VR/SGS, t T + T, and t has xponntal dstrbuton wth th dnsty functon ƒ(t) and wth man /µ. Th probablty that thr ar n ADRs durng th MS rsdnc n th VR/SGS s, K ) Θ(,, t )?t) dt (4) t 0 By usng aplac transform functon, for a functon ƒ(t) dfnd on 0 t, ts aplac transform functon s dnotd as: l{ f ( t )} F ( S ) st f ( t ) dt t 0 Whr s s a ral numbr () + { } (-)* ( λt), K ) -λt?t) dt t 0 [( n )* + ]! Authntcaton & Ky Establshmnt. Usr Authntcaton Rqust, K) (λλt (-)*+ [(n ) * + ]! t 0 t (-)+?t) - λt dt (6) 4. Usr Authntcaton Rspons Fgur Authntcatons and Ky Agrmnt Protocol. Analytcal Modl for th Currnt AKA wth Fxd ngth () for AVs Th Posson dstrbuton formula can b usd to dtrmn th probablty of authntcaton vnts arrvng such as locaton updat (rgstraton), call orgnaton and call trmnaton. t λ b th constant that rprsnts th avrag rat of arrvals vnt. Accordng to Posson probablty n an ntrval of lngth T, th probablty of mass functon (pmf) s λt ( λt ) k P{ X k } k) k! Whr k0,,2 () And th cumulatv dstrbuton functon (cdf) s x λt ( λt ) k P{ X k } G( x ) (2) K k!, K ) ( λt) (-)*+ [( n )* + ] d F(s) (-)+ (-)*+ (-) (-)+! ds s λ () Thus s th numbr of ADRs that has a Posson dstrbuton, th avrag numbr of ADRs whn th MS rsds n th VR/SGS s E [ ] *, ) (8) And th total cost for transmsson on AV s C [ ] E[ ].( + 2. α ) () Whr 2α s th cost of transmsson from th VR/SGS to HR/AuC to back to th VR/SGS. In our papr w assumd that th rsdnc tm t of MS n VR/SGS s xponntal dstrbuton. Th gnral formula for th probablty dnsty functon (pdf) of th xponntal dstrbuton s µ. t f ( x) µ. By usng quaton () and (8) to drv th n,k) and E[] for xponntal dstrbuton [], s, K) ( ) (0)

3 2 IJCSS Intrnatonal Journal of Computr Scnc and twork Scurty, VO.6 o.b, March 2006 E ] [ () By usng quaton (), th total cost of transmsson on AV s + 2 * α C[ ] (2) Fg, 4 rprsnt our analyss and smulaton rsults. Ths fgurs show how th xpctd ADRs numbr E[] and th cost of total ADRs transmsson C(K) ar ffctd by th authntcaton vctor sz () and arrval rat λ. Whn th numbr of rcords ncrasd n AV thn th xpctd numbr of ADRs wll b dcrasd. Fg. shows that th rlatonshp btwn th and E[] s ndrctly proportonal, and th rlatonshp btwn arrval rat λ and E[] s drctly proportonal. Fg. 4 shows that th rlatonshp btwn arrval rat λ and C[] s drctly proportonal. But Fg., 4 and shown that thr s optmal valu for that dpnds on th arrval rat λ, and f s ncrasd mor than optmal valu for, thn t dos not mprov th E[] prformanc. 4. Analytcal Modl for th Proposd AKA wth Dynamc lngth () for AVs Hr, w dscuss how to slct optmal valu of for AV. Ths valus ar affctd by th followng factors:. Th rsdnc tm of MS n VR/SGS. 2. umbr of usr authntcaton rqusts and rspons UARs and Data authntcaton rqust and rspons ADRs.. Avrag rat of arrvals vnt. W assumd that thr s fld n HR/AuC that w can stor n t th optmal valu for of AV for ach MS, ths valu dpnds on th hstory of UARs and DARs for th MS. For nw MS th ntal valu for as rcommndd by GPP. Hr wll dscuss two cass; on of thm s th MS whch stays n th sam VR/SGS whl AV s turnd out.. a nw ADRs s rqustd, and anothr cas s MS movng to nw VR/SGS. Cas : MS stayng n th sam VR/SGS Th HR/AuC s rsponsbl for stor th ssu tm T for th th authntcaton data rqust and rspons ADR, whn AV s turnd out and nw ADRs s rqustd at tm T +, thn HR/AuC comput arrval rat whch s qual to th numbr of UARs ar usd dvdd by (T + - T ), and xcut th followng algorthm to fnd th optmal valu of. Dpndng on th arrval rat λ for th prvous UARs, th followng procdur s xcutd to comput. For xampl f thr ar vnts pr 2 mnuts thn arrval rat 2. vnts/mnuts. Procdur to fnd optmal valu for th ngth of AV Mnmum cost Countr J Found Tru Whl found Tru do Comput cost for J by usng quaton 2 If cost [] ss than mnmum cost thn Els End f End whl Optmal valu Mnmum cost cost[] Incrmnt countr J Found Fals and stop xcuton Fg. 4 llustrat th rsult of our smulaton to gt th optmal valu for λ 40 and Fg. 6 llustrats th cost for optmal valu. In Fg. 4, w hav classfd th optmal valu for ach arrval rat λ, But f you tak th avrag of arrval rat thn w gt most optmal valu wth optmal cost. Th HR/AuC comput arrval rat whch s qual to th numbr of UARs usd dvdd by (T + - T ), lt th computd arrval rat s λ +. Thn calculat th avrag arrval rat λ av (λ + λ + )/2 and thn xcut th abov algorthm to fnd optmal valu of as shown n Fg. 6. Cas 2: MS movng to nw VR/SGS In ths cas, thy wll fnd th optmal valu of, whn MS movs from VR/SGS to nw VR/SGS. Th VR/SGS s rsponsbl to count th numbr of UARs whch ar xcutd durng th tm MS stayd n t. Whn th MS movs to nw VR/SGS or dtachs from th ntwork, thn th old VR/SGS must provd th numbr of UARs to th HR/AuC. Also th HR/AuC s rsponsbl for storng th last optmal valu of that s assgnd to MS. Howvr, th ntal optmal valu assgnd to MS whn th frst tm s as suggstd by GPP. t MS s stayng n j th VR/SGS and ( s th optmal valu that s slctd to MS and thr ar of UARs ar countd by j th VR/SGS. Whn th MS lavs th j th VR/SGS ara, thn th optmal valu of must b computd by HR/AuC and gnrat AV wth optmal sz. Th nw valu of s computd as followng ( or ( j + ) 2 ( or ( + Ths dpnds to th avrag of cost for, 2 and, whr th cost of, whr s computd accordng th followng formula: C ( + 2α ) for,2, Thn Avrag ( j + ) s whr s, and Cs s narast to C As shown n Fg., th costs of (c ), whr, ar clos to ach othr. From our smulaton th bst prformanc s achvd whn w slct whos s cost clos to avrag, rathr than whos cost s mnmum. Th optmal s stord n HR/AuC to b usd n nxt tm for ntal ADRs.

4 IJCSS Intrnatonal Journal of Computr Scnc and twork Scurty, VO.6 o.b, March Concluson Th proposd dynamc lngth for AV whn compard to th currntly usd fxd lngth for AV, found to b rducng th authntcaton traffc ovrhad btwn MS and authntcaton cntr, and th authntcaton latncy from nd usr s pont of vw, and th nrgy consumpton of a mobl trmnal. Th transmsson of ADRs btwn HR/AuC and VR/SGS s usually xpnsv; ncrasng th for AV s rducng th numbr of ADRs rqust. But, f s too larg, th AVs may consum ntwork bandwdth for ach ADRs rqust. From our smulaton and analyss, w hav shown that ncrasng th numbr of rcords n AV wll dcras th numbr of ADRs, but thr ar lmts to ncrasng. Also th cost s dcrasd whn s ncrasd, but th crtcal pont happns whn s ncrasd, whn cost wll b ncrasd as wll. Hnc w nd to stck to choosng an optmal valu of n AV. Th analyss of th modl analytcally and by smulaton has producd an optmal n ths dynamc AV. E[] Expctd umbr of ADRs Effctd of Arrval Rat and ngth of AV to ADRs (ngth of AV) Optmal Optmal Valu for Authntcaton Vctor Arrval Rat Fgur Optmal Valus for Authntcaton Vctor Optmal Valu for Authntcaton Vctor and th Cost for Optmal Optmal Cost of optmal Arrval Rat λ4 λ8 λ2 λ6 λ20 λ24 Fgur Expctd numbrs of ADRs durng MS rsds n VR/SGS Cost of th Total ADR Transmsson Fgur 6 Optmal Valus for Authntcaton Vctor and Cost Cost C() λ4 λ8 λ2 λ6 λ20 λ Optmal Valu for Authntcaton Vctor whn comput Avrag λ Optmal optmal w th Avrag λ ngth of AV () 2 Fgur 4 Cost of th Total ADR Transmsson Arrval Rat Fgur Optmal Valus for Authntcaton Vctor whn comput Avrag λ Rfrncs []. Y-Bng n, Yuan-Ka Chn, "Rducng authntcaton sgnalng traffc n thrd-gnraton mobl ntwork", IEEE Transactons on Wrlss Communcatons, vol. 2, no., May 200 pp. 4-0

5 4 IJCSS Intrnatonal Journal of Computr Scnc and twork Scurty, VO.6 o.b, March 2006 [2]. Mark Johnson, Rvnu Assuranc, Fraud and Scurty n G Tlcom Srvcs, VP Busnss Dvlopmnt Vsual Wrlss AB, Journal of Economc Managmnt, Fall 2002, Volum, Issu 2, [].. Salgarll, M. Buddhkot, J. Garay, S. Patl, and S. Mllr. Th Evaluaton of wrlss As and PAs Effcnt Authntcaton and Ky Dstrbuton n Wrlss IP tworks. IEEE Prsonal Communcaton on Wrlss Communcaton 0(6):2-6, Dcmbr 200. [4]. GPP TS 2.. GPP Scurty; Scurty Archtctur. []. Muxang Zhang and Yuguang Fang Scurty Analyss and Enhancmnts of GPP Authntcaton and Ky Agrmnt Protocol, IEEE.Transacons on wrlss communcatons, Vol, 4, O. 2, March 200. [6]. Watson, E.J. aplac Transforms and Applcatons, Brkhausrk, 8. Ja afr A-Sararh rcvd th BSc dgr n computr scnc from Mu tah Unvrsty, Karak, Jordan, n 4. H rcvd th MSc dgr n computr scnc form Unvrsty of Jordan, Amman, Jordan, n H s currntlt a PhD studnt n th Faculty of Scnc and Tchnology at Angla Ruskn Unvrsty, UK. Hs rsarch ntrsts nclud mobl and wrlss ntwork scurty.