Enabling Public Audit Ability and Data Dynamics for Storage Security in Cloud Computing Data Integrity Proofs In Cloud Storage

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1 IOSR Jurnal f Cmputr Engnrng (IOSRJCE) ISSN: , ISBN: Vlum 6, Issu 1 (Sp-Oct. 2012), PP Enablng Publc Audt Ablty and Data Dynamcs fr Strag Scurty n Clud Cmputng Data Intgrty Prfs In Clud Strag K.C Rav Kumar 1, E.Krshnavn Rddy 2, Pryanka Rakam 3 1, 2, 3 (Cs, Sr Dv Wmn s Engnrng Cllg, Hydrabad, Andhra Pradsh, Inda) Abstract: IT has mvd nt nxt gnratn wth clud cmputng bng ralzd. Th way applcatn sftwar and databass ar strd has bn changd. Nw thy ar strd n clud data cntrs n whch scurty s a cncrn frm clnt pnt f vw. Th nw phnmnn whch s usd t str and manag data wthut captal nvstmnt has brught many scurty challngs whch ar nt thrughly undrstd. Ths papr fcuss n th scurty and ntgrty f data strd n clud data srvrs. Th data ntgrty vrfcatn s dn by usng a thrd party audtr wh s authrzd t chck ntgrty f data prdcally n bhalf f clnt. Th clnt f th data gts ntfcatns frm thrd party audtr whn data ntgrty s lst. Nt nly vrfcatn f data ntgrty, th prpsd systm als supprts data dynamcs. Th wrk that has bn dn n ths ln lacks data dynamcs and tru publc audtablty. Th audtng task mntrs data mdfcatns, nsrtns and dltns. Th prpsd systm s capabl f supprtng bth publc audtablty and data dynamcs. Th rvw f ltratur has rvald th prblms wth xstng systms and that s th mtvatn bhnd takng up ths wrk. Mrkl Hash Tr s usd t mprv blck lvl authntcatn. In rdr t handl audtng tasks smultanusly, blnar aggrgat sgnatur s usd. Ths nabls TPA t prfrm audtng cncurrntly fr multpl clnts. Th xprmnts rval that th prpsd systm s vry ffcnt and als scur. Indx Trms: Clud cmputng, publc audt ablty, clud strag, clud srvc prvdr I. Intrductn Varus trnds ar pnng up th ra f Clud cmputng. Clud cmputng s a dvlpmnt that s ntrnt basd and us f cmputr tchnlgy. Th mst chapr as wll as pwrful prcssrs, alng wth th sftwar as a srvc (SaaS) archtctur f cmputng, ar abl t transfrm data cntrs nt cmputng srvc pls n a larg scal. Th ncrasng bandwdth f th ntwrk as wll as rlabl als flxbl cnnctns f th ntwrk maks t mr pssbl that clnts can b abl t subscrb srvcs f hgh-qualty frm data alng wth sftwar that rsd nly n rmt data cntrs. Evn thugh vsualzd as a prmsng platfrm f srvc fr th Intrnt, ths nw paradgm f data strag n Clud pssss many challngng dsgn ssus that hav gratr nflunc n th scurty as wll as prfrmanc f th whl systm. Th vrfcatn f data ntgrty at ntrustd srvrs s n f th man cncrns n cas f clud data strag. Fr slvng th prblm whch nvlvs data ntgrty vrfcatn, many schms ar prpsd undr varus systms and scurty mdls [1], [2], [3], [4], [5], [6], [7], [8], [9], and [10]. In all ths systms, grat ffrts ar put fr dsgnng slutns that mt svral rqurmnts lk hgh schm ffcncy, vrfcatn that s statlss, us f qurs whch s unbundd and data rtrvablty, tc. In th mdl, basd n th vrfr rl, all th abv schms fall nt tw dffrnt catgrs. Thy ar prvat audtablty and publc audtablty.thugh schms that fall nt prvat audtablty catgry ar abl t achv hghr schm ffcncy, th schms that blng t publc audtablty catgry prmts anyn, nt smply th clnt r data wnr, t addrss th srvr f th clud fr accuracy f data strag whl mantanng n prsnal nfrmatn. Thn, t s pssbl fr clnts ar t dlgat th srvc prfrmanc valuatn t an ndpndnt thrd party audtr (TPA), wth n dvtn f thr rsurcs f cmputatn. Th clnts thmslvs ar unrlabl n th clud r nt abl t addrss th vrhad whch nvlvs carryng ut ntgrty chcks mr frquntly. Anthr mprtant cncrn amng arlr dsgns s that f prvdng supprt t data pratn dynamcally fr applcatns f clud data strag. Th prpsd systm dals wth mtvatn f th publc audtng systm f data strag scurty n Clud Cmputng, and dvlps a prtcl that supprts fr cmpltly dynamc data pratns, partcularly fr supprtng blck nsrtn, whch s a drawback n mst f th xstng schms. Als th systm s xtndd fr supprtng scalabl as wll as ffctv publc audtng n Clud Cmputng. T b n partcular, th schm s abl t achv batch audtng n whch multpl numbrs f dlgatd audtng tasks frm varus usrs can b carrd ut n a paralll mannr by th TPA. Th scurty rlatd t prpsd schm s prvd and th prfrmanc f th schm s justfd thrugh cncrt mplmntatn as wll as valuatn wth th stat f th art. 6 Pag

2 II. Rlatd Wrk Nwadays, a larg amunt f grwng ntrst s pursud n th ara f vrfcatn f rmtly strd data n [1], [2], [3], [4], [5], [6], [7], [8], [9], [11], [12], [13], and [14]. Atns t al. [2] ar th frst fr cnsdrng publc audtablty n thr rspctv mdl f prvabl data pssssn t nsur pssssn f fls n strags that ar nt trustd. In thr mdl, thy usd hmmrphc tags that ar RSA-basd fr audtng data whch s ut surcd; hnc publc audtablty has bn achvd. Mrvr, Atns t al. hav nt cnsdrd th cntxt that nvlvs strag f dynamc data, and xtndng thr schm frm statc data strag t dynamc strag n a drct mannr can rsult n dsgn as wll as scurty prblms. In [12], Wang t al. hav takn nt accunt dynamc data strag n a scnar whch s dstrbutd, and thr challng-rspns prtcl s abl t dtrmn bth th data crrctnss as wll as lcatn f pssbl rrrs. Juls and Kalsk [2] prpsd a mdl f prf f rtrvablty, whr spt-chckng as wll as rrr-crrctng cds hav bn usd fr nsurng bth pssssn as wll as data fls rtrvablty n archv srvc systms. Thugh th xstng systms strv fr prvdng vrfcatn f ntgrty fr varus systms f data strag, th ssu that nvlvs supprtng publc audtablty as wll as data dynamcs s nt fully addrssd. III. Prblm Dscrptn Th prpsd systm archtctur s as shwn n fg. 1. Th ntts n th prpsd ntwrk ar clnt, clud strag srvr and thrd party audtr. Clnt s an ndvdual r rganzatn wh dpnds n clud srvc prvdr fr strng data fls and mantanng thm. Th clud strag srvr s havng lt f strag spac and cmputatnal rsurcs. It s mantand by clud srvc prvdr. Thrd party audtr s trustd and has capablts f audtng th clnt s data n dmand. Scurty ssag flw TPA Scurty mssag flw Scurty mssag flw Fg. 1 shws prpsd archtctur Clud Srvc Prvdr As can b sn n fg. 1, t s vdnt that clnts str thr data nt clud strag srvrs prvdd by clud srvc prvdr. clnts Ths mdl assums tw thngs. Thy ar a) th clud data prvdr may dlt fls f clnt. B) Clud data prvdr may hd ptntal prblms n th data cntr. Kpng ths assumptns n mnd, th mchansms n th prpsd systm ar dsgnd. IV. Scurty Mchansms In th prpsd scurty md, th TPA prdcally challngs th clud strag srvr n rdr t fnd whthr th data strd n srvr s scur. Ths mdl s basd n th mdl prpsd n [3]. Othr xstng slutns ar [1], [2], and [3]. Hwvr, th slutn prpsd n ths papr dffrs frm thm n th vrfcatn prcss. Mrvr ths schms d nt supprt blck nsrtn and dynamc data pratns. Th man rasn s that sgnatur cnstructn nds nfrmatn n fl ndx. R-cmputng wth nw ndxs nc a blck s 7 Pag

3 nsrtd has t b dn whch causs mvr vrhad. T vrcm ths prblm, th ndx nfrmatn s rmvd n th cmputatn f sgnaturs. Th tag usd H(m) fr blck m nstad f usng H(nam ) as usd n [3] and h(v ) [2]. Thrfr t dsn t affct thr up n ndvdual data pratn n any fl. In th prpsd schm th clnt s nt gvn any prvlg t calculat H(m) wthut data. Ths s knwn as blcklss vrfcatn. In rdr t achv, th srvr taks rspnsblty f cmputng H(m) and gv t back t prvr. Th scurty rsk n ths apprach s that th advrsars ar gvn mr pprtunts t chat th prvr by gnratng m r H(m). Th dsgn gals f th systm ar strag crrctnss assuranc thrugh publc audtablty, supprt fr dynamc data pratns, and blcklss vrfcatn. V. Prpsd Slutn Kpng th rsarch gals spcfd n th abv sctn, ths papr ntrducs a nw schm fr nsurng scurty f clnt data strd n clud strag srvr. Th prtcl dvlpd supprts publc audtablty wth dynamc data pratns. Scurty Analyss Th prpsd systm nabls publc audtablty wthut nd fr rtrvng data blcks f a fl. Twards ths hmmrphc authntcatr tchnqu [1] [3] s usd. Thr s th unfrgabl mtadata gnratr cmputd frm ndvdual data blcks. In th prpsd wrk tw authntcatrs such as BLS sgnatur [3] and RSA sgnatur basd authntcatr. Th scurty mchansm s furthr dscrbd hr. Th prcdur f prtcl s dvdd nt stup, dfault ntgratn vrfcatn and dynamc data pratn wth ntgrty assuranc. In th last stp, data mdfcatn, data nsrtn, and data dltn ar a part. Latr n batch prcssng wth multclnt data s als dscussd hr. Stup In ths phas KyGn() mthd s nvkd t gnrat publc ky and prvat ky. SgGn() s mant fr pr-prcssng and hmmrphc authntcatrs and alng wth mta data. Th SgGn() mthd taks tw argumnts namly scrt ky and fl. Th fl cntnt s dvdd nt blcks. Thn sgnatur s cmputd fr ach blck. Each blck s hash cd s takn and tw nds hash s mrgd nt n n rdr t gnrat th nxt nd. Ths prcss cntnus fr all laf nds untl tr nd s fund. Th rt lmnt s thn takn by clnt and sgns t and snd t clud strag srvr. Data Intgrty Vrfcatn Th cntnt f utsurcd data can b vrfd by thr clnt r TPA. Ths s dn by challngng srvr by gvng sm fl and blck randmly. Up n th challng, th clud strag srvr cmputs th rt hash cd fr th gvn fl and blcks and thn rturns th cmputd rt hash cd and rgnally strd hash cd alng wth sgnatur. Thn th TPA r clnt uss publc ky and prvat ky n rdr t dcrypt th cntnt and cmpar th rt hash cd wth th rt hash cd rturnd by clnt. Ths prcdur s spcfd n th fllwng algrthm. 1. Start 2. TPA gnrats a randm st 3. CSS cmputs rt hash cd basd n th flnam/blcks nput 4. CSS cmputs th rgnally strd valu 5. TPA dcrypts th gvn cntnt and cmpars wth gnratd rt hash 6. Aftr vrfcatn, th TPA can dtrmn whthr th ntgrty s brachd. 7. Stp Tabl 1 shws th algrthm fr data ntgrty vrfcatn Data Mdfcatn and Data Insrtn Data mdfcatns ar th frqunt pratns n clud strag. It s a prcss f rplacng spcfd blcks wth nw ns. Th data mdfcatn pratn can t affct th lgc structur f clnt s data. Anthr pratn s knwn as data nsrtn. Data Insrtn s a prcss f nsrtng nw rcrd n t xstng data. Th nw blcks ar nsrtd nt spcfd lcatns r blcks n th data fl F. Th prcdur fr mdfcatn and nsrtn s gvn n Tabl 2. 8 Pag

4 1. Start 2. Clnt gnrats nw Hash fr tr thn snds t t CSS 3. CSS updats F and cmputs nw R 4. Clnt cmputs R 5. Clnt vrfs sgnatur. If t fals utput s FALSE 6. Cmput nw R and vrfy th updat and Tabl 2 shws algrthm fr updatng and dltng data prsnt n CSS Batch Audtng fr Mult-clnt Data Clud srvrs supprt smultanus accss. It ds man that n srvr t s pssbl t hav dffrnt vrfcatn sssns runnng parallly. Thrfr t s ssntal t hav audtng functnalty that wrks cncurrntly fr many usr sssns. Th prpsd schm s xtndd t achv ths fr prvabl data updats and vrfcatn f mult-clnt systm. Hr an mprtant dcsn mad s t mak us f Blaraggrgat Sgnatur Schm [15]. ` ` VI. Dsgn Cnsdratns Th man dsgn cnsdratn s t achv audtablty and data dynamcs. Th slutn s BLS basd and t can als b dn wth RSA basd sgnaturs. BLS slutn s 160 bts whr as RSA s f 1024 bts. Shrtst qury and rspns s pssbl wth BLS. RSA als supprts varabl szd blcks. MHT (Mrkl Hash Tr) has t b usd t achv th slutn. Th thr dsgn cnsdratn s data dynamcs. T achv data dynamcs PDP and PR schms can b xtndd. Hwvr, thy hav scurty prblms. As dscussd arlr an advrsary can ntrud and prfrm pratns wth as unlss, H(nam ) s changd fr ach updat pratn. Mdfcatns ar dn n th xstng blcks whl nsrtn can b dn at any pnt n F dntng a fl whch has bn savd t clud strag srvr. In basc PDP cnstructns th systm strs statc fls wthut rrr crrctn capablts. Th prpsd schm ams at dsgnng a blcklss and statlss vrfcatn f data. Ths s mprtant as th TPA ds nt nd actual data. Th actual data s nt shwn t anyn. Only hash valus and scur kys ar usd fr vrfcatn nstad f actual data. Yt anthr dsgn cnsdratn s t supprt dstrbutd strag scurty. Whn data f clnts ar strd n multpl clud srvrs, t nds a mchansm t rtrv such data and manag data. Th data s duplcatd at many placs t wthstand faults. Th gvn fl F s strd n multpl clud strag srvrs. VII. Prfrmanc Analyss Th prpsd schm and als such wrks dn n th ltratur sarch ar prsntd n tabl 3. Th rgnal PDP schm [1] s xtndd by [13] n rdr t supprt data dynamcs wth du authntcatn. Thus th prpsd schm s als knwn as DPPP schm. RSA-basd scurty algrthm and als BLS wr mplmntd. Th tst bd usd s IntlCr2 prcssr wth 2.4 GHz HDD and 768 MB RAM. Varus data ntgrty chckng tls that mntr data rmtly ar gathrd and tabulatd. Thy ar thn cmpard wth th prpsd algrthm prfrmanc f ths papr. Tabl 3 shws th cmparsn dtals. Mtrc/Schm [2] [4] [12]* [14] Our Schm Data Dynamcs N N Ys Ys Ys Publc Ys Ys N N Ys Audtablty Srvr cmp. 0(1) 0(1) 0(1) 0(lg 0(lg n) cmplxty n) Vrfr cmp. 0(1) 0(1) 0(1) 0(lg 0(lg n) cmplxty n) Cmm. 0(1) 0(1) 0(1) 0(lg 0(lg n) Cmplxty n) Vrfr strag 0(1) 0(1) 0(1) 0(1) 0(1) cmplxty Tabl 3 shws rsults f varus tls 9 Pag

5 Enablng Publc Audt ablty and Data Dynamcs fr Strag Scurty n Clud Cmputng Data As can b sn n tabl 3, th cmparsn rsults shw that ur schm s supprtng data dynamcs and als publc audtablty whl thr tls ar supprtng thr data dynamc r publc audtablty but nt bth. Ths shws that ur prpsd systm s bttr than xstng ns C m m u n c a t n C s t Blck Sz (KB) RSA-BASED DPRP Fg. 2 shws cmmuncatn cst vr blck sz As can b sn n fg. 2, t s vdnt that th prpsd RSA basd schm cmmuncatn cst f DPRP schm s mr whn cmpard wth th prpsd RSA basd schm. RSA basd apprach s yldng mr prfrmanc. A v r a g a u d t 100% 80% 60% 40% 20% 0% Batchd Indvdual Numbr f clnts n th systm Fg. 3 shws avrag audtng tm pr clnt As can b sn n fg. 3, numbr f clnts n th systm and avrag audtng tm pr clnt ar plttd n x and y axs rspctvly. Th ndvdual apprach s shwng bttr prfrmanc whn cmpard wth batch apprach. N u m b r f c l n Avrag audtng tm pr clnt(ms) Indvdual Batchd Fg. 4 shws avrag audtng tm pr clnt As can b sn n fg. 4, numbr f clnts n th systm and avrag audtng tm pr clnt ar plttd n x and y axs rspctvly. Th ndvdual apprach s shwng bttr prfrmanc whn cmpard wth batch apprach. VIII. Cnclusn Fr nsurng scurty f clud data strag, t s dffcult fr nablng a TPA fr valuatng th qualty f srvc frm an bjctv and ndpndnt pnt f vw. Publc audtablty s abl t allw clnts fr dlgatng th tasks f ntgrty vrfcatn t TPA whl thy ar ndpndntly nt rlabl r cannt cmmt 10 Pag

6 rqurd rsurcs f cmputatn prfrmng vrfcatns n a cntnuus mannr. On mr mprtant cncrn s th prcdur fr cnstructn f vrfcatn prtcls whch can b abl t accmmdat data fls that ar dynamc. In ths papr, th prblm f mplyng smultanus publc audtablty and data dynamcs fr rmt data ntgrty chck n Clud Cmputng s xplrd. Th cnstructn s dsgnd fr mtng ths tw man gals but ffcncy s st as th man gal. Fr achvng data dynamcs that ar ffctv, th xstng prf f strag mdls s nhancd thrugh manpulatn f th cnstructn f classc Mrkl Hash Tr fr authntcatn f blck tag. Fr supprtng gd handlng f multpl numbrs f audtng tasks, th mthd f blnar aggrgat sgnatur s furthr xplrd fr xtndng th man rsult nt a multusr sttng, whr TPA s abl t prfrm multpl audtng tasks n a smultanus mannr. Hug scurty as wll as prfrmanc analyss prvs that th prpsd schm s ffcnt and scur t a gratr xtnt. Rfrncs [1] G. Atns, R. Burns, R. Curtmla, J. Hrrng, L. Kssnr, Z.Ptrsn, and D. Sng, Prvabl Data Pssssn at UntrustdStrs, Prc. 14th ACM Cnf. Cmputr and Cmm. Scurty (CCS 07), pp , [2] A. Juls and B.S. Kalsk Jr., Prs: Prfs f Rtrvablty frlarg Fls, Prc. 14th ACM Cnf. Cmputr and Cmm. Scurty(CCS 07), pp , [3] H. Shacham and B. Watrs, Cmpact Prfs f Rtrvablty, Prc. 14th Int l Cnf. Thry and Applcatn f Cryptlgy andinfrmatn Scurty: Advancs n Cryptlgy (ASIACRYPT 08),pp , [4] K.D. Bwrs, A. Juls, and A. Opra, Prfs f Rtrvablty:Thry and Implmntatn, Rprt 2008/175, Cryptlgy PrntArchv, [5] M. Nar and G.N. Rthblum, Th Cmplxty f Onln MmryChckng, Prc. 46th Ann. IEEE Symp. Fundatns f CmputrScnc (FOCS 05), pp , [6] E.-C. Chang and J. Xu, Rmt Intgrty Chck wth DshnstStrag Srvr, Prc. 13th Eurpan Symp. Rsarch n CmputrScurty (ESORICS 08), pp , [7] M.A. Shah, R. Swamnathan, and M. Bakr, Prvacy-PrsrvngAudt and Extractn f Dgtal Cntnts, Rprt 2008/186,Cryptlgy Prnt Archv, [8] A. Opra, M.K. Rtr, and K. Yang, Spac-Effcnt Blck Strag Intgrty, Prc. 12th Ann. Ntwrk and Dstrbutd Systm Scurty Symp. (NDSS 05), [9] T. Schwarz and E.L. Mllr, Str, Frgt, and Chck: UsngAlgbrac Sgnaturs t Chck Rmtly Admnstrd Strag, Prc. 26th IEEE Int l Cnf. Dstrbutd Cmputng Systms (ICDCS 06), p. 12, [10] Q. Wang, K. Rn, W. Lu, and Y. Zhang, Dpndabl and Scur Snsr Data Strag wth Dynamc Intgrty Assuranc, Prc.IEEE INFOCOM, pp , Apr [11] G. Atns, R.D. Ptr, L.V. Mancn, and G. Tsudk, Scalabland Effcnt Prvabl Data Pssssn, Prc. Furth Int l Cnf.Scurty and Prvacy n Cmm. Ntwrks (ScurCmm 08), pp. 1-10,2008. [12] C. Wang, Q. Wang, K. Rn, and W. Lu, Ensurng Data StragScurty n Clud Cmputng, Prc. 17th Int l Wrkshp Qualty f Srvc (IWQS 09), [13] C. Erway, A. Kupcu, C. Papamanthu, and R. Tamassa, Dynamc Prvabl Data Pssssn, Prc. 16th ACM Cnf.Cmputr and Cmm. Scurty (CCS 09), [14] K.D. Bwrs, A. Juls, and A. Opra, Hal: A Hgh-Avalabltyand Intgrty Layr fr Clud Strag, Prc. 16th ACM Cnf.Cmputr and Cmm. Scurty (CCS 09), pp , [15] D. Bnh, C. Gntry, B. Lynn, and H. Shacham, Aggrgat andvrfably Encryptd Sgnaturs frm Blnar Maps, Prc. 22 nd Int l Cnf. Thry and Applcatns f Cryptgraphc tchnqus (Eurcrypt 03), pp , Authr Dtals: K.C Rav Kumar M.Tch CSE frm JNTU Hdrabad currntly h s th had f dpartmnt fr M.Tch CSE prgramm n SrDv Wmn s Engnrng Cllg havng 17 yars f Acadmc Exprnc. H s lf mmbr f IEEE & IST aras f rsarch nclud Data Mnng & Data Warhusng Infrmatn Rtrval Systms Infrmatn Scurty. Mrs.E.Krshnavn Rddy M.Tch(S.E) B.Tch(C.S.E), currntly sh s Assstant Prfssr f C.S.E Dpartmnt n SrDv Wmn s Engnrng Cllg. Ms. Pryanka Rakam B.Tch (C.S.E) frm Sndhura Cllg f ngnrng and Tchnlgy 11 Pag