International Journal of Scientific & Engineering Research, Volume 5, Issue 12, December-2014 1631
ISSN 2229-5518
Cipher-text Security from Cipher text Policy
Attribute Based Encryption in cloud computing
#1 Udaya Priya Darsini., #2 Mrs.S.Geofrin Shirly , #3 Dr.S.Neduncheliyan
PG Student, Department Of Computer Science and Engineering#1, Assistant Professor, Department Of Computer Science and Engineering#2
Director, Department Of Computer Science and Engineering#3
School of Engineering, Vels University,Chennai,India
Priyadarsini.udaya@gmail.com#1,geofrin55@yahoo.co.in#2,director.secs@velsuniv.org#3
A bs t r ac t - T h e h o t t ech n o l o g y o f cu rren t t r e nd t o s t o r e bul k i nf o r m a t i o n i n a v i r t ua l m e m o r y i s c l o ud c o m put i ng . U s i ng t hi s t e c hno l o g y t he da t a o w ne r s ecu res t h e i n f o rm a t i o n i n cl o u d s erv er. T o s ecu ri t y co n cern , s o m a n y cry p t o g ra p h i c t ech n i q u es a re a v a i l a b l e. B ut m o s t o f t he s e t e c hni que s f a i l e d t o d el i v er s ecu ri t y a g a i n s t t h e i n f o rm a t i o n s t o red i n cl o u d s er v er. T o o b t ai n d at a c o n f id e n t ia l it y , s c a la b il it y , f le x ib i li t y , a n d f i n e g ra i n ed a cces s co n t ro l i n s t o red
I n de x T e r m s — da t a c o nf i de nt i a l i t y ,
C l o ud i s di s t r i but i ng s e r v i c e s t hr o ug h i nt e r ne t [ 8, 9] . I t i s a n i nt e r ne t ba s e d c o m put a t io n a l e n v ir o n m e n t s o th a t pa ym e n t is o n l y fo r re s o u rc e s t h a t a r e u s ed . A s et o f p o o l ed r es o u r c es ar e de l i v e r e d t hr o ug h t he i nt e r ne t t o i ndi v i dua l s a nd bus i ne s s e s . F o r a n ex am p l e, t he c l ou d i s pr ovi d i n g s e r vi c e s f o r b u s in e s s a p p l ic a tio n s , f ile s to r a g e , s o c ia l s ite s , a n d m a i lin g . T h e m a jo r a n d v e r y i m p o r t a nt pr o f i t o f c l o ud c o m put i ng is c o m p a c t c o s t, c a p ita l e x p e n d itu r e a n d I T c a p a b ilit ie s .
T he 69% o f U S c i t i z e ns a do pt e d c l o ud s e r v i c e s o n 2008 S e pt e m be r ; t hi s
s t udy i s d o ne b y P e w R e s e a r c h I ns t i t ut e [7 ]. A s w el l as t h e g o v er n m en t o f U S i s s p e n d in g lo t o f b illio n s in c lo u d c o m put i ng w hi c h a ppr o xi m a t e l y r e a c he s
t he a m o unt $7 bi l l i o n by t he ye a r 2015. I n d ia is a g r o w in g c o u n tr y, it n e v e r f a ils
t o g r o w i n t he f ut ur e c o m put i ng e nv i r o nm e nt l i ke c l o ud. M o s t of t h e I ndi a n c om p a n i e s a r e f ol l ow i n g c l ou d , f or a n e xa m pl e B ha r a t i , A s ho k L e yl a nd, I n f o s y s a nd t he y i nhe r i t t he s e r v i c e s f r o m M i c r o s of t a nd C i s c o W e bE x. T he c l o ud i s
us e d by g ov e r nm e nt s , s i ng l e us e r , bi g a nd s m a ll o r g a n iz a tio n s . T h e c lo u d is p r o v id in g a ll typ e s of s e r v i c e s t ha t c a n be a f f o r da bl e t o o r di na r y pe o pl e .
C l o ud s e r v e r i s a n un - t r u s t e d a r e a be c a us e o f hug e num be r o f us e r s . T he s e c u r ity a g a in s t th e s to r e d in f o r m a tio n is bi g g e s t que s t i o n m a r k i n c l o ud [ 9, 10 ] . I f
t he i nf o r m a t i o n i n c l o ud i s s e c ur e t he n i t s h o u ld m e e t th e f o llo w in g c r ite r ia ; d a ta c o n f id e n tia li ty, s c a la b ili ty, f le x ib ility a n d ac c es s co n t r o l .
• DAT A CO NF I D E N T IAL IT Y
T he da t a o w ne r s t o r e s t he i nf o r m a t i o n i n a c l o ud s e r v e r . T he s t o r e d
i nf o r m a t i o n s ho ul d be s e c ur e f o r t ha t t he i nf o r m a t i o n s ho ul d be e nc r ypt e d be f o r e upl o a di ng i n t he c l o ud s e r v e r . S o t ha t , t he una ut he n t i c a t e d us e r c a n no t br e a k t h e e nc r ypt e d i nf o r m a t i o n.
• SCAL AB IL IT Y
T h e s c al ab i l i t y i s d et er m i n ed b y t h e s ys t em p er f o r m an c e. T h e p o o l a ut he nt i c a t e d us e r s c a n no t i nf l u e n c e t h e s ys t em p er f o r m an c e. F o r an ex am p l e, t h e num be r o f a ut he nt i c a t e d us e r c a n i nc r e a s e
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International Journal of Scientific & Engineering Research, Volume 5, Issue 12, December-2014 1632
ISSN 2229-5518
i n c l o ud but t hi s w i l l ne v e r a nd e v e r a f f e c t t h e ef f i c i en cy o f s ys t em p er f o r m an c e.
• F L E XIB IL IT Y
T he c l o ud i s a f l e xi bl e e n v ir o n m e n t. I t a llo w s th e a u th e n tic a te d u s er t o u s e e x t r a r es o u r c es at p eak t i m e a ls o . T h e f le x ib i li ty o f c l o u d is r e a l ly h ig h b ec au s e i f t h e au t h en t i c at ed u s er h a s an y pr o bl e m i n da y t o da y o pe r a t i o n t he n i t i s r ec o v er ed .
• F INE G RAI NE D ACCE SS CO NT RO L
I n c l o ud, t he p oo l o f a ut he nt i c a t e d us e r i s i n s am e t eam t h e s ys t em i s s u e uni que r i g ht s t o i ndi v i dua l u s e r .
C l ou d i s s u c h a b i gge s t s t or a ge ar ea w h er e t h e s t o r ed i n f o r m at i o n d o es n o t h av e an y g u ar an t ee t h at s h o u l d b e s ec u r e [ 9, 10] . T he i nf o r m a t i o n s t o r e d i n t he c l o ud s h o ul d be s e c ur e d f r o m t he o t he r us e r s a nd t he c l o ud pr ov i de r i t s e l f . T hi s
t he m o s t i m po r t a nt c o ndi t i o n a ppl i e d f o r s e c ur i t y i n c l o ud. T hi s c o ndi t i o n t og e t he r w ith f le x ib ili ty a n d a c c e s s c o n tr o l g iv e s da t a c o nf i de nt i a l i t y. F o r a n e xa m pl e , t he
c o n f id e n tia l in f o r m a tio n o f a u s e r t r a ns f e r e d t o t he c l ou d f r om t h e c o m m on ar ea a nd t he i nf o r m a t i o n c a n be ba nk a c t i v i t i e s , pi n no , he a l t h r e c o r d a nd s o o n. T h e a c c e s s c o n tr o l is th e m o s t im p o r ta n t s e c u r ity t o p ic a n d v a r io u s s e c u r ity mo d e ls ar e al s o av ai l ab l e i n t h e m o d er n
t e c hno l og i c a l e r a . B ut w hi c he v e r pr o v i de s d a ta c o n f id e n tia li ty, s c a la b ili ty,
f le x ib il ity, a c c e s s c o n tr o l in b e s t w a y is t h e ef f i c i en t s ec u r i t y s c h em e.
I n t hi s pa pe r w e d i s c us s a bo ut t he
s e c ur i t y pl a n of A B E a nd c o m pa r e t he t w o
i m po r t a nt s e c ur i t y s c he m e K P - A B E w ith CP - A B E a nd a l s o t o ac h i ev e d at a c o n f id e n tia li ty, s c a la b ili ty, f le x ib ili ty, ac c es s co n t r o l w e i m p l em en t C P - AB E i n
s to r e d in f o r m a tio n .
I f a s c h e m e a c h ie v e d f le x ib ili ty, fi n e - g r ai n ed ac c es s co n t r o l an d s c al ab i l i t y t he n t ha t s ho ul d be a b es t s c h em e f o r d at a c o n f id e n tia li ty. F o r th is lo ts o f s c h e m e s ar e av ai l ab l e b u t t h es e w o r k s a r e do ne i n s i m i l a r t r us t e d do m a i n [ 1, 2] . T h a t is t h e da t a o w ne r s a nd c l o ud pr o v i de r s s ho ul d be
in th e s im ila r d o m a in . I n th e o th e r h a n d , in
c l o ud t he da t a o w ne r s a nd c l o ud pr o v i de r s ar e i n t h e d i f f er en t d o m ai n .
A t t r i but e ba s e d e nc r ypt i o n i s ne w ac c es s c o n t r o l s c h em e d ev el o p ed b y S ah ai an d W at er s f o r d at a co n f i d en t i al i t y. T o
en h an c e t h es e w o r k G o yal et al . ad d ed a fi n e - g r a i ne d a c c e s s c o nt r o l i n A B E s c he m e . D e pe ndi ng upo n t hi s a c c e s s c o n tr o l th e c lo u d p r o v id e r a llo w s th e u s e r to a c c e s s in f o r m a tio n in c lo u d .
A B E i s us e d t o c o nque r f i ne g r ai n ed ac c es s c o n t r o l o v er u s er i nf o r m a t i o n [ 9] . I f hu g e num be r of us e r s
a c c e s s i ng c l o ud f r o m di f f e r e nt do m a i n
th e n th e A B E is q u ite d if f ic u lt to h a n d le t h e k ey m an ag em en t . T h e A B E s c h em e i s c la s s if ie d in to tw o t yp e s . T h e f ir s t s c h em e o f A B E i s Ke y P o l i c y AB E ( KP - A B E ) . In t h e KP - A B E s c h e m e t h e s et o f at t r i b u t es t r a ns f o r m t o c i phe r t e xt a nd t he m o no t o ni c
t r ee ac c es s s t r u c t u r e i s u s ed t o f o r m
p r i v at e k ey. T h e p r i v at e k ey c h an g es t h e e n c r yp te d in f o r m a tio n to o r ig in a l in f o r m a tio n . S o th a t th e K P - A B E pr ov i de s
f i n e g r ai n ed acc es s co n t r o l o n u s er i nf o r m a t i o n. I n o t he r ha nd , t he K P - AB E s c h em e d o es n o t h av e f l ex i b i l i t y o n e x e c u tin g th e a ttr ib u te s a n d th e s c a la b il ity a l s o ha s bi g i s s ue s . T he i s s ue i n
s c a la b il ity is n o th in g b u t it is n o t p o ssi b l e t o w o r ks o n m ul t i pl e us e r s .
A f t e r unde r s t a ndi ng K P - AB E s c h em e [ 4 ] , w e c an i d en t i f y t h e n ec es s i t y of t he C i phe r t e x t P o l i c y A B E . T he s c he m e CP - A B E ag ai n s t K P - A B E pr ov e s t ha t C P - A B E s c h em e co n s i s t o f b es t ac c es s c o n t r o l a n d it is a c h ie v in g s c a la b ili t y a n d
f le x ib il ity a s w e ll d a ta c o n f id e n tia l ity
be t t e r t he n K P - A B E s c h em e.
F o r de a l i ng i nf o r m a t i o n s ha r i ng a nd f i ne g r a i n e d a c c e s s c o nt r o l i n c l o ud a ne w c r ypt og r a phi c s c he m e i s a v a i l a bl e w hi c h pr ov i de s a po t e nt i a l to o l th a t is A ttr ib u te - ba s e d e nc r ypt i o n ( A B E ) [ 6 ] . O ne of t he f i ne s t s c he m e s o f A B E i s t o e n c r ypt a nd de c r ypt i nf o r m a t i o n i s K P - A B E . T h e k e y p o lic y a ttr ib u te b a s e d e n c r yp tio n c o n s is ts o f s e t o f a ttr ib u te s in th e c ip h e r
t e xt . T he de c r ypt i o n ke y l i nke d w ith m o n o t o n ic tr e e a c c e s s s tr u c tu r e , w h ic h is us e d t o de c r ypt t he c i phe r t e xt . I n t he un -
t r us t e d c l o ud s t o r a g e K P - A B E is p la yin g
a n i m po r t a nt r o l e i n d a t a s ha r i ng .
S til l, th is K P - A B E s c he m e i s no t w o r ki ng o n s c a l a bi l i t y a nd a s i t ha s m u ltip le - l ev el s o f at t r ib u te a u th o r it ie s a n d
IJSER © 2014 http://www.ijser.org
International Journal of Scientific & Engineering Research, Volume 5, Issue 12, December-2014 1633
ISSN 2229-5518
it is h ig h l y im p o s s ib le to le a d to f le x ib il ity. A c c o r d in g to th is in K P - AB E i s n o t p o s s ib le to a c h ie v e s c a la b ili ty a n d
f le x ib il ity s o th a t th e a c c e s s c o n tr o l is b ig que s t i o n m a r k .
I n a t t r i but e ba s e d e nc r ypt i o n t he w o r ki ng pr i nc i pl e o f C P - A B E is to ta lly d i ffe r e n t fr o m K P - A B E [ 5 ] . A c c o r di ng t o KP - A B E s c he m e t he ke ys of c i phe r t e xt a nd de c r ypt i o n ke y a r e s hi f t e d i n C P - AB E . T h e en c r yp t o r c h o o s es t h e t r e e ac c es s po l i c y t o e nc r y pt t he c i phe r t e x t . D e pe ndi ng upo n t he s e t of a t t r i but e s t he s ec r et k ey i s c r eat ed . T h e s ec r et k ey a llo w s to d e c o d e th e c ip h e r te x t, if th e g iv e n c ip h e r te x t m a tc h e s w ith th e s e t o f at t r i b u t es c o n n ec t ed w i t h a s ec r et k ey,
th e n it f u lf ills th e t r e e a c c e s s p o lic y.
C P - A B E s c h em e i s t h eo r et i c al l y c l o s er t o w el l es t ab l i s h ed s c h em es l i k e RB A C ( R o l e - B as ed A cc es s C o n t r o l ) be c a us e o f us e r s de c r ypt i o n ke ys a r e r e la te d w ith th e s e t o f a ttr ib u te s . S o th a t, th is i s m o s t r e le v a n t s c h e m e th a t e x p lo its CP - A B E as an al t er n at i v e o f KP - AB E , w h ic h w ill im p o s e a c c e s s c o n tr o l o f e nc r ypt e d da t a .
F r o m th is , c ip h e r te x t p o lic y a t t r i but e ba s e d e nc r ypt i o n ( C P - AB E ) i s undo ubt e dl y o ne t he be s t s c he m e a g a i ns t k e y p ol i c y ( K P - A B E ) b ec au s e o f i t i s ex p r es s i v en es s i n d es c r i b i n g ac c es s c on t r ol p ol i c i e s .
• K e y m an a g em en t : T h e c l as s i c al m o d el t o s e c u r e t h e ou t s ou r c e d d a t a i n a c om m on s to r a g e lik e c lo u d is to s to r e e n c r yp te d da t a , s o t ha t t he de c r ypt i o n ke ys ha nde d ov e r t o t he a ut ho r i z e d us e r s . T he s e de c i s i o ns m a y c a u se l o t s o f se c u r i t y i ssu e s in c la s s ic a l m o d e l [ 1 - 6] . S o t o pr ov i de
s e c u r ity a g a in s t th is p r o b le m a n d to
a llo c a te d e c r yp tio n k e ys to a u th o r iz e d u s er s , a w el l o r g an i z ed k e y m an ag e m en t s ys t e m i s ne e de d . D ue t o t he w o r ki ng p r in c ip le o f th e tw o a t tr ib u te b a s e d e nc r ypt i o n ( C P - AB E & K P - A B E ) w e c an unde r s t a nd t ha t C P - A B E i s ha v i ng t he be s t ke y m a na g e m e nt s ys t e m de pe ndi ng o n t he s e t o f a ttr ib u te in th e d e c r yp tio n k e y i f it s a ti s f ie s tr e e a c c e s s p o lic y lin k e d w ith c i phe r t e xt , t he ke y i s us e d t o de c r y pt t he
c i phe r t e xt . B ut i n K P - A B E , w hi c h ha s v er y p o o r at t r i b u t e m an ag em en t , t h i s i s s u e r e s u l te d la c k o f f le x ib ili ty.
• S c a la b ili ty a n d F le x ib il ity : T he of f i c i a l us e r s be c o m e bul k y, t he r e s ul t s ho ul d be w e l l - o r g a ni z e d. T he C P - AB E s c h em e i s ef f i c i en t o n e i f t h e au t h o r i z ed us e r s i nc r e a s e d i n c l o ud. B ut i n K P - AB E s c h em e i f t h e au t h o r i z ed u s er s ar e
i nc r e a s e d t h e r e s u l t s ho ul d no t be e f f i c i e nt . T he a ut ho r i z e d us e r s a r e i nc r e a s e d i n c l o ud t ha t pr e v i o us l y v a l i d us e r s ho ul d be r e v o ke d a nd t he da t a ha s t o be r e - e nc r ypt e d. F o r t he e x is tin g v a lid us e r t he n e w ke ys m us t be i s s u e d.
D e pe ndi ng o n t he a c c e s s c o nt r o l s ys t e m
KP - A B E i n c l o ud, pr o v i de a r e - e nc r ypt i o n
te c h n iq u e . S o th a t , K e y P o lic y A ttr ib u te B as ed E n c r yp t i o n av ai l s a f i n e - g r a i ne d ac c es s co n t r o l . C o r r e s po ndi ng t o a n a c c e s s st r u c tu r e a s e t o f a ttr ib u t e s in K e y P o lic y A t t r i but e B a s e d E nc r ypt i o n ha s a publ i c k e y. T h e f i l es ar e en c r yp t ed b y D E K ( s y m m e tr ic d a ta e n c r yp tio n k e y) th a t is
us e d t o t w i s t e nc r ypt e d publ i c ke y be c a us e of t he num be r o f a t t r i but e s i n K P - A B E , it i s c r eat ed b y a n a c c e s s s t r u c t u r e . T h e e nc r ypt e d D E K a nd t he c o r r e s po ndi ng a t t r i but e s s t o r e d w i t h t he e nc r ypt e d da t a f ile s . I n c l o u d th e s e t o f a ttr ib u te s o f f ile s t o r e d t ha t s ho ul d be c o nt r o l l e d by t he a c c e s s s t r uc t ur e o f us e r ’ s ke y, s o t ha t o nl y
t he us e r c a n de c r ypt t h e D E K , t h at i s u s ed tw is t in g th e d e c r yp t f ile .
A K e y P o lic y A ttr ib u te B a s e d E nc r ypt i o n t o s e c ur e i nf o r m a t i o n i s i m pl e m e nt e d by t he e n c r ypt i o n ke y s of
d at a f i l es . T h i s s t r u c t u r e s t r ai g h t aw ay h av e t h e b en ef i t o f f i n e g r ai n acc es s
c on t r ol . CP - A B E s c h em e, de c o di ng ke ys o nl y s uppo r t us e r a t t r i but e s t h a t a r e o r g an i z ed l o g i c al l y as a s i n g l e s et , s o us e r s c a n o nl y us e a l l po s s i bl e c o m b in a tio n s o f a ttr ib u te s in a s in g le s e t is s u e d in th e ir k e ys to s a tis f y p o lic ie s
a ≡ g k ( m o d p ) ; g c d ( k , p - 1 ) = 1 ; e l s e a ≡ 1 ?
Me s s ag e M ( di g r a ph, t r i g r a ph b l o c ks )
P ubl i c ke y ( g , p, y ≡ g x ( m o d p) ) M ≡ ( x a
+ kb) m o d ( p - 1)
w h e r e x = p r i v a t e k e y
k = r a ndom s e c r e t v a l ue
D ig ita l S ig n a tu r e ( a , b ) s e n t w i th M
y aab ≡ g M ( m o d p) T h e M at h :
g M ≡ g ( xa + kb) m o d p
( g x) a ( g k) b ≡ ya a b ( m o d p)
If M i s m o di f i e d, c o n g r ue nc e w o ul d be v i o l a t e d. S o t ha t i n K P - AB E f i n e g r a in a c c e s s c o n tr o l is q u ite d if f ic u lt to
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International Journal of Scientific & Engineering Research, Volume 5, Issue 12, December-2014 1634
ISSN 2229-5518
a c hi e v e . B ut i n C P - A B E is q u ite s im p le to ac h i ev e f i n e g r ai n ac c es s c o n t r o l .
AB E | S c a l - a b il ity | Fl e x i - b ili ty | A cc es s c on t r ol | D at a C on f i d e n - tia li ty |
KP - AB E | f ai l ed | l ow | l ow | f ai l ed |
CP - AB E | h i gh | h i gh | h i gh | ac h i ev ed |
F i g: 1 c o m pa r i ng A B E s c he m e s
In K P - A B E s c he m e , t he e nc r ypt o r c a n n ot c o m e t o a c on c l u s i on w h o c a n de c r ypt t he e nc r ypt e d da t a e xc l udi ng d e s c r ip tiv e a t t r i but e s f o r t he da t a , a nd no o t he r w a y t he e nc r ypt o r m us t t r us t t h e ke y i s s ue r . A nd m o r e ov e r , t he s c he m e K P - AB E
is n o t c o n v e n ie n t to th e s e typ e s o f a ppl i c a t i o n. S o t ha t i n t he s e t ype s of a p p lic a tio n s th e m o s t e f f i c ie n t e n c r yp tio n s c he m e i s t ha t t he us e r s d e sc r i b e s v a r i o u s a t t r i but e s a nd t he o ne w ho s e a t t r i bu t e s m at c h a p o l i cy as s o c i at ed w i t h a c i p h er
t e xt c a n de c r ypt t he c i phe r t e xt . F o r s uc h an ap p l i c at i o n , a b et t er c h o i c e i s C P - AB E . F r o m th e ta b le f ig : 1 , w e c a n id e n tif y th a t CP - A B E is a c h ie v e d f le x ib ility, s c a la b il ity an d f i n e g r ai n ed acc es s co n t r o l , s o t h at i t p r o v id e d a ta c o n f id e n tia lity to th e o ut s o ur c e d da t a i n c l o ud c o m put i ng .
An A ttr ib u te B a s e d E n c r yp tio n in c l o ud c o m put i ng , v a r i o us c o n c e pt s a nd a ls o th e c la s s if ic a tio n o f A B E a r e di s c us s e d. A nd a l s o i n a br i e f m a nne r t he ke y p o l i c y A B E a nd c i phe r t e xt po l i c y AB E ar e d i s c u s s ed . T he w o r ki ng pr i nc i pl e o f K P - AB E i s co m p ar ed w ith C P - A BE a n d c a m e t o a n c o n c l us i o n w hi c h o ne i s pr o v i di ng s e c ur e i nf o r m a t i o n i n c l o ud c o m put i ng . F in a l ly we h av e ac h i ev ed d at a c o n f id e n tia li ty, s c a la b ili ty, f le x ib ility a n d f i ne g r a i ne d a c c e s s c o nt r o l t hr o u g h C P - A B E a g a in s t K P - AB E .
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