Co
m
pu
ter Sci
ence a
nd Inf
or
mat
i
on
Tec
h
no
lo
gies
Vo
l.
1
, No
.
2
,
J
ul
y
2020
,
pp.
78
~
83
IS
S
N:
27
22
-
3221
,
DOI: 10
.11
591
/
csi
t.v
1i
2
.p
78
-
83
78
Journ
al h
om
e
page
:
http:
//
ia
esprime
.com/i
ndex.
php/csit
High
s
ec
urity me
chanism
: fragme
ntation a
nd
re
pli
cation in
the clou
d with a
uto upd
ate in th
e system
Shrut
ik
a Kh
obra
gade,
R
oh
i
ni Bhos
ale,
R
ahul
J
iw
ane
Depa
rtment
o
f
C
om
pute
r
Engi
n
e
eri
ng,
Mum
bai
Univer
sit
y
,
Pill
a
i
HO
C
Coll
ege
o
f
Engoneeri
ng
a
nd
Technol
og
y
,
Rasa
y
ani,
Dist
.
Rai
gad
,
Mah
ara
s
htra
,
Indi
a
Art
ic
le
In
f
o
ABSTR
A
CT
Art
ic
le
history:
Re
cei
ved
Ja
n 2
2,
20
2
0
Re
vised
Ma
y
1
0
, 2
0
2
0
Accepte
d
Ma
y
2
5
, 20
2
0
Cloud
Com
puti
n
g
m
ake
s
imm
ense
use
of
in
te
rn
e
t
to
stor
e
a
huge
amount
of
dat
a
.
C
loud
co
m
puti
ng
provid
es
high
qua
li
t
y
servi
ce
with
l
ow
cost
and
sca
la
b
il
i
t
y
wi
th
le
ss
r
equi
r
ement
of
har
dwar
e
and
software
m
ana
gement.
Secur
ity
pla
y
s
a
vital
role
in
c
l
oud
as
d
at
a
is
h
andl
ed
b
y
thi
rd
par
t
y
h
ence
sec
urity
is
the
bi
ggest
concern
to
m
at
te
r.
Thi
s
pro
posed
m
ec
hani
s
m
foc
uses
on
the
se
cur
ity
issues
on
th
e
cl
oud.
As
the
f
ile
is
st
ore
d
a
t
a
par
ticu
la
r
loc
a
ti
o
n
which
m
ight
ge
t
aff
e
cted
due
t
o
at
t
ac
k
and
wi
ll
lost
th
e
da
ta.
So,
in
thi
s
prop
osed
work
inste
ad
of
stor
i
ng
a
complete
f
il
e
at
a
p
art
i
cular
lo
cation,
the
fi
le
is
div
id
ed
int
o
fra
gm
en
ts
and
e
ac
h
fra
gm
ent
is
stored
at
v
ari
ous
loc
a
ti
ons.
Frag
m
ent
s
are
m
ore
sec
ure
d
b
y
p
ro
vidi
ng
th
e
hash
ke
y
to
each
fra
gm
ent
.
Th
is
m
ec
hani
sm
wil
l
not
r
eve
al
a
ll
t
he
informati
on
reg
ard
ing
a
par
ticula
r
f
il
e
ev
en
after
succ
essful
at
t
ac
k
.
Here
,
t
he
r
eplication
of
fra
gm
en
ts
is
a
lso
g
ene
r
at
e
d
with
strong
a
uthe
ntica
ti
on
pr
oce
ss
using
ke
y
gen
erati
on
.
The
aut
o
upd
ate
of
a
fra
gm
ent
o
r
an
y
f
il
e
is
al
so
done
h
ere.
Th
e
conc
ep
t
of
aut
o
update
of
fi
ll
es
is
done
wher
e
a
file
or
a
fr
ag
m
ent
c
an
be
upd
at
ed
onl
ine.
Instea
d
of
downloadi
ng
th
e
whole
file,
a
fra
g
m
ent
c
an
be
do
wnloade
d
t
o
updat
e
.
More
tim
e
is sa
ved
usin
g
thi
s m
et
hodo
lo
g
y
.
Ke
yw
or
d
s
:
Au
t
o update m
echan
ism
Cl
oud
sec
ur
it
y
Fil
e fr
a
gm
entation
Fil
e rep
li
cat
ion
Ver
si
on contr
ol
This
is an
open
acc
ess arti
cl
e
un
der
the
CC
B
Y
-
SA
l
ic
ense
.
Corres
pond
in
g
Aut
h
or
:
Ra
hu
l Ji
wan
e
,
Dep
a
rtm
ent o
f C
om
pu
te
r
E
ng
i
neer
i
ng,
Mum
bai U
niv
e
rsity
,
Pil
la
i HO
C C
ol
le
ge
of E
ngon
eerin
g
a
nd Tec
hnology
, Rasa
ya
ni,
Dist.
Rai
gad, Ma
har
as
ht
ra,
I
ndia
.
Em
a
il
: rj
iwane
@m
es.ac.in
1.
INTROD
U
CTION
Cl
oud
com
pu
ti
ng
encl
os
es m
or
e
us
e
of n
et
w
orkin
g
sit
es a
nd o
t
her f
or
m
s of inter
perso
nal
com
pu
ti
ng
.
Howe
ver,
ther
e
are
a
la
rg
e
a
m
ou
nt
of
resour
ces
on
cl
oud
stora
ge,
data
or
s
of
t
war
e
a
ppli
cat
ion
s
wh
i
ch
ha
ve
been
acce
sse
d on
li
ne
. I
t play
s
an
im
po
rtant role
in
the
pri
va
cy
an
d
sec
ur
it
y
of
t
he
data. A
s
cl
oud
com
pu
ti
ng
is
a
flexi
ble,
c
os
t
-
ef
fecti
ve
a
nd
authe
ntica
te
d
de
li
ver
y
platf
orm
fo
r
pro
vid
i
ng
bu
si
ness
c
on
su
m
er
IT
se
rv
i
ces
on
the
inter
net.
Cl
oud
C
om
pu
ti
ng
prese
nts
an
a
dd
e
d
le
vel
of
r
isk
as
esse
ntial
serv
ic
es
a
re
oft
en
ou
ts
ource
d
to
a
third
par
ty
,
wh
i
ch
m
akes
it
diffi
cult
to
m
ai
ntain
data
sec
ur
it
y
and
pr
i
vacy,
de
m
o
ns
trat
e
con
s
ent
an
d
al
so
s
uppo
rt
data
a
nd
se
rv
i
ce
avail
a
bili
ty
.
T
he
cl
oud
co
m
pu
ti
ng
par
a
di
gm
has
re
f
orm
ed
the
c
on
tr
ol
a
nd
m
anag
e
m
ent
of
the
inf
orm
ation
te
ch
nolo
gy
inf
rastr
uctu
re
[
1].
Cl
oud
c
ompu
ti
ng
is
c
ha
ra
ct
erized
by
on
-
dem
and
sel
f
-
se
rv
ic
es
,
resou
rce
po
oling,
el
ast
ic
it
y,
ub
i
qu
it
ous
net
work
acce
sses
and
m
easur
ed
ass
ur
a
nce
of
the
se
rv
ic
es
[2
,
3].
Howe
ver,
the
ben
e
fits
of
im
per
ce
ptible
m
anag
em
ent
(
fro
m
us
er’
s
pe
rs
pecti
ve),
l
ow
cost,
ea
sy
acc
ess
a
nd
gr
eat
er
r
esi
li
en
ce com
e w
it
h
i
ncr
ease
d sec
uri
ty
co
nce
rn
s
wh
i
ch
ha
ve
t
o be t
aken care
of.
Erstw
hile,
c
om
pu
te
r
softwa
re
was
not
wr
i
tt
en
with
sec
uri
ty
in
m
ind
bu
t
beca
us
e
of
t
he
inc
reasin
g
fr
e
qu
e
ncy
a
nd
s
ophisti
cat
ion
of
m
alici
ou
s
at
ta
cks
agai
nst
inf
orm
ation
syst
em
s,
m
od
er
n
softwa
re
de
sig
n
Evaluation Warning : The document was created with Spire.PDF for Python.
Com
pu
t. Sci.
I
nf. Tec
hnol.
High sec
ur
it
y
mecha
nism: fr
agme
nta
ti
on
and re
plicati
on
in the cl
oud w
it
h
… (
Sh
r
utika
Khobr
agade
)
79
m
et
ho
dolo
gies
include
sec
ur
i
t
y
as
a
pri
m
ary
obj
ect
ive
.
W
it
h
cl
oud
c
om
pu
ti
ng
syst
em
s
seekin
g
t
o
m
eet
m
ulti
ple
obj
ect
ives
,
su
c
h
as
cost,
perf
orm
ance,
reli
abi
li
ty
,
m
ai
ntainabili
ty
,
an
d
secu
rity
,
tra
de
-
offs
hav
e
t
o
be
m
ade.
An
y
cl
oud
se
rv
e
r
is
vu
l
ner
a
ble
to
an
at
ta
cke
r
wit
h
unli
m
i
te
d
ti
m
e
and
ph
ysi
c
al
acce
ss
to
th
e
ser
ver
.
A
dd
it
ion
al
ly
,
ph
ysi
cal
pro
blem
s
cou
ld
ca
us
e
the
s
er
ver
to
ha
ve
dow
n
ti
m
e.
This
w
ould
be
a
los
s
of
avail
abili
ty
,
wh
ic
h
i
s
on
e
of the
key
pr
in
ci
ples of the
se
cur
it
y t
riad
con
fide
ntial
it
y, int
egr
it
y, a
nd av
a
il
abili
ty
(
CIA)
.
The
data
wh
ic
h
is
ou
ts
ource
d
to
a
public
cl
oud
m
us
t
be
se
cur
e
d.
U
na
uthorize
d
data
acc
ess
by
oth
e
r
us
ers
a
nd
diff
e
ren
t
proces
ses
(can
be
acci
de
ntal
or
delibe
r
at
e)
s
hould
be
pr
e
ve
nted
[
4].
As
sta
te
d
a
bove
,
a
ny
weak
entit
y
m
ay
le
ad
the
whol
e
cl
oud
at
ris
k.
In
s
uc
h
a
fr
am
ework,
the
secu
r
it
y
m
echan
is
m
sh
oul
d
sig
nific
antly
increase
a
hac
ker’s
e
ffor
t
t
o
retrieve
a
pr
obable
am
ou
nt
of
data
w
hich
m
ay
get
lost
even
after
a
s
uc
cessf
ul
intru
si
on
or
at
ta
ck
in
the
cl
ou
d.
Mo
re
ov
e
r,
t
he
reas
onable
a
m
ou
nt
of
l
os
s
(due
to
data
le
akag
e
)
m
us
t
al
so
be
m
ini
m
iz
ed.
A.
Me
i
Et
al
.
[
5]
s
ay
s
that
t
he
sch
e
m
e
of
fr
a
gm
e
ntati
on
a
nd
repl
ic
at
ion
to
al
loc
at
e
file
s
over
m
ulti
pl
e
serv
e
rs
can
le
a
d
t
o
a
ny
at
ta
ck
as
t
he
file
s
wi
ll
be
store
d
at
the
par
ti
cula
r
l
ocati
on.
Ju
el
s
et
al
.
[6
]
prese
nted
a
te
chn
iq
ue
cal
le
d
a
s
Ir
is
file
syst
e
m
wh
ic
h
e
nsures
t
he
fr
es
hness,
inte
gr
it
y
and
a
vaila
bili
ty
of
data
i
n
a
cl
oud.
G
Ka
ppes
et
al
.
[7
]
w
he
re
the
de
li
ber
at
e
at
ta
ck
of
ce
nsori
ou
s
i
nfor
m
at
ion
in
c
ase
of
im
pr
ope
r
saniti
zat
ion
c
annot
be han
dled
. It
s
tores
t
he
file
base
d o
n bloc
ks
wh
ic
h
m
ay
lea
d
to
an i
m
pr
oper s
a
niti
zat
ion
.
The
ou
ts
ource
d
e
nv
ir
onm
ent
where
t
he
use
of
a
tr
us
te
d
t
hi
rd
par
ty
pr
ov
i
des
the
secu
rity
serv
ic
es
i
n
the
cl
ou
d
is
a
dvocated
in
A
ddressi
ng
Cl
oud
Com
pu
ti
ng
Secu
rity
Iss
ue
s
[
2].
T
hey
us
e
d
the
pu
blic
key
infr
a
struct
ur
e
(
PK
I
)
t
o
e
nh
a
nc
e
the
tr
us
tw
ort
hin
ess
in
t
he
a
uth
e
ntica
ti
on
,
integ
rity
and
co
nf
i
den
ti
al
it
y
of
data
.
At
the
use
r
le
ve
l,
the
us
e
of
t
a
m
per
-
pro
of
de
vices,
s
uch
a
s
s
m
art
card
s
w
as
us
e
d
as
the
stora
ge
of
the
keys.
Y.
Ta
ng
et
al
.
[
8]
hav
e
util
iz
e
d
t
he
public
ke
y
crypt
ography
an
d
tr
us
te
d
thi
rd
par
ty
for
pr
ov
i
ding
data
se
cur
it
y
in
cl
oud
e
nvir
on
m
ents.
H
ow
ever,
the
a
uthor
has
not
us
e
d
the
PKI
in
frast
ru
ct
ure
to
r
edu
ce
the
over
heads
.
The
syst
em
need
s
to
be
m
or
e secur
e
an
d
s
ho
uld
b
e
acce
sse
d
by
only
aut
horize
d
per
s
on. Th
e d
at
a
sto
re
d
in
the
cl
oud
need
to
secur
e
as
well
as
pro
pe
r
e
ncry
ption
keys
ha
ve
to
be
us
ed
for
the
ve
rifica
ti
on
of
file
whic
h
is
store
d
in
it
.
2.
PROP
OSE
D SYSTE
M MO
DEL
A
new
pr
opose
d
m
od
el
e
ns
ures
the
sec
ur
it
y
of
the
data
wh
ic
h
i
s
st
or
e
d
on
the
cl
oud.
T
his
syst
em
pro
vid
es
t
he
be
tt
er
so
luti
on
to incr
ease
t
he
se
cur
it
y
as w
el
l
a
s
pe
rfor
m
ance level.
T
he
cl
ou
d
sec
ur
it
y
inc
r
eases
by
the
co
ntr
ol o
f
thir
d
-
pa
rty
a
dm
inist
rati
ve
con
t
ro
l.
T
he
dat
a
w
hich
ne
eds
to
be
sec
ured
is
in
the form
of f
il
es.
Dive
rse
am
ou
nt
of
file
s
a
re
sto
red
on
cl
oud
s
o
he
re
a
pa
rtic
ular
file
is
uploa
ded
an
d
t
hen
f
r
agm
entat
ion
pr
oces
s
is
done.
Eac
h
fr
a
gm
ent
of
th
at
file
is
secure
d
with
ha
sh
key
w
hich
is
gen
e
rated
ra
ndom
l
y.
Fr
agm
ents
a
r
e
gen
e
rated
base
d
on
e
qual
siz
e
an
d
eac
h
f
ragm
ent
of
t
hat
pa
rtic
ular
file
is
placed
at
a
di
f
fer
e
nt
locat
io
n.
Here
con
t
ro
ll
ed
re
plica
ti
on
is
m
ai
ntained
w
her
e
ea
ch
fr
a
gm
ent
is
rep
li
cat
ed
only
once
t
o
im
pr
ove
the
sec
ur
it
y.
Wh
en
an
at
ta
cke
r/
ha
cker
hack
s
that
sp
eci
fied
file
,
he
will
not
re
ve
al
al
l
the
i
nfo
rm
ation
of
that
file
.
Va
rio
us
a
tt
acks
su
c
h
as
data
r
ecov
e
ry,
cr
os
s
VM
at
ta
ck,
i
m
pr
op
er
m
edia
sa
niti
zat
ion
,
VM
esca
pe
ca
n
be
ha
ndle
d
by
this
m
et
ho
dolo
gy.
I
n
t
his
pro
po
se
d
syst
em
,
a
file
is
up
l
oad
e
d
on
t
he
cl
oud
w
hi
ch
needs
to
be
secu
re
d
as
it
i
s
thir
d
par
ty
o
uts
ourc
ed
data.
A
file
is
ge
ner
al
ly
sto
red
on
a
cl
oud at
a p
arti
cular
l
ocati
on w
hic
h
is
not
sec
ur
e
d as
any
at
ta
cker
can
ea
sil
y
acce
ss
or
at
ta
ck
that
par
t
ic
ular
file
an
d
get
the
i
nfor
m
at
ion
us
i
ng
vari
ou
s
m
al
ic
iou
s
at
ta
ck
or
i
ntrusio
n.
S
o
inste
a
d
of
sto
rin
g
a
sin
gle
file
at
a
par
ti
cula
r
locat
io
n,
a
file
is
fr
a
gm
ented
accor
ding
to
t
he
siz
e
and
placed
at
t
he
di
ff
e
ren
t
lo
cat
ion
s
o
that
if
any
at
ta
cker
acce
ss
to
that
par
ti
cula
r
file
it
will
no
t
re
ve
al
al
l
the
inf
or
m
at
ion
of
that
w
ho
l
e
file
.
Secu
rit
y
is
the
m
ajo
r
c
on
ce
r
n
w
her
e
a
file
m
us
t
be
purely
secur
e
d,
so
to
m
ai
ntain
this,
each
key
is
us
e
d
for
dif
fere
nt
fr
a
gm
ent
of
a
s
ing
le
file
.
Re
pl
ic
a
of
file
is
al
so
m
ai
ntained
to
ge
t
avail
abili
ty
o
f
l
os
t fil
e
or o
l
d
f
il
es.
2.1.
Design
go
als
of clo
ud
c
ompu
ting
Desig
n
go
al
s
of
cl
oud
c
om
pu
t
ing
a
re
sta
te
d
t
o
pr
ov
i
des
good
aut
he
ntica
ti
on
syst
em
wh
ic
h
al
lo
ws
only
auth
or
iz
e
d
us
e
rs
t
o
l
og
i
n
a
nd
process
.
Im
pr
oves
secu
rity
as
well
as
im
pr
ov
es
the
pe
rfo
rm
ance.
Fra
gm
entat
ion
of
file
is
create
d
to
a
nd
each
fr
a
gm
ent
is
st
or
e
d
at
di
ff
e
re
nt
locat
io
n.
C
ontr
olled
re
plica
ti
on
is
de
vel
oped
t
o
decr
ease
t
he
ch
ance
of
data
lo
ss,
increa
ses
th
e
perform
ance,
avail
abili
ty
and
reli
abili
ty
.
To
pro
vid
e
a
file
to
th
e
cl
ie
nt w
he
ne
ve
r
the
re
will
b
e
run
ti
m
e err
or i
n netw
ork.
As
il
lustrate
d
i
n
F
i
gure
1
,
in
the
de
sig
n,
firs
t
reg
ist
rati
on
proces
s
is
done
by
gi
ving
t
he
i
nfor
m
at
ion
about
the
us
er
.
Au
t
horized
use
r
will
log
in
t
o
the
syst
e
m
.
Pr
opos
e
d
syst
em
prov
i
des
be
st
way
for
the
se
cur
e
d
file
s
w
hich
is
ve
ry
susc
eptible
f
or
at
ta
c
ks
.
Us
er
need
s
to
upl
o
ad
the
file
on
the
syst
em
by
pro
vid
in
g
Fil
e
Id
an
d
Fil
e
Nam
e.
The
uploa
ded
file
gets
f
ra
gm
ent
ed
in
su
c
h
a
w
ay
that
fr
a
gm
e
nts
do
not
incl
ud
e
any
m
eaningf
ul
inf
or
m
at
ion
as
a
pa
rtic
ular
if
fr
a
gm
ented
an
d
eac
h
fr
a
gm
e
nt
nee
ds
it
s
own
enc
ryptio
n
key.
F
ra
gm
ent
at
i
on
i
s
done
by
usi
ng
the
eq
ual
siz
e
of
file
an
d
if
not
of
e
qu
al
siz
e
then
rem
ai
nin
g
byte
s
of
file
is
store
d
at
t
he
nex
t
fr
a
gm
ent. Th
is helps
to
kee
p away
the att
acker fr
om
f
ind
in
g
the locati
on
of
eac
h
f
ra
gm
e
nt as each
fr
a
gm
ent is
store
d
at
diff
e
r
ent
locat
io
n.
H
ere
eac
h
key
is
gen
e
rated
f
or
e
ach
f
ra
gm
ent
from
the
con
te
nt
of
t
he
file
so
t
ha
t
an
Evaluation Warning : The document was created with Spire.PDF for Python.
IS
S
N
:
2722
-
3221
Com
pu
t. Sci.
I
nf. Tec
hnol.
,
V
ol.
1
, N
o.
2
,
J
ul
y
20
20
:
78
–
83
80
at
ta
cker
will
not
get
the
data
of
each
fr
a
gm
e
nt.
Fr
a
gm
ents
will
be
place
d
at
dif
fer
e
nt
node
s
as
it
will
be
diff
ic
ult
for
th
e
at
ta
cke
r
to
acce
ss
on
sin
gle
file
.
A
fter
t
h
e
fr
a
gme
ntati
on
proc
e
ss
that
fr
a
gm
e
nts
get
re
plica
te
d
on
diff
e
re
nt
nodes
in
su
c
h a
way
that
the
acce
ss
tim
e
will
be l
ow
w
hich al
s
o i
ncr
ease
s
the
pe
rfor
m
ance. Pr
opose
d
syst
e
m
pr
ovid
es
the
c
on
t
rol
le
d
rep
li
cat
io
n
w
hic
h
is
r
equ
i
red
t
o
m
anag
e
the
i
de
al
perform
a
nce
an
d
m
or
e secur
it
y.
Figure
1
.
Pro
pose
d
arc
hitec
tu
re
3.
PROP
OSE
D SYSTE
M
TE
CHNIQ
UE
The
ste
ps
of A
l
gorithm
are
as
fo
ll
ows:
a.
Fr
a
gm
ent Placem
ent
The i
niti
al
ste
p
is
s
el
ect
the
fil
e
f
oe
fr
a
gm
ent.
Sele
ct
the
pa
rt
ic
ular
file
w
hic
h
nee
ds
t
o
be
fragm
ented.
The
file
gets
f
r
agm
ented
base
d
on
the
siz
e.
Each
f
rag
m
ent
is
stored
at
th
e
diff
e
ren
t
loc
at
ion
i.e
on
di
f
fer
e
nt
nodes
.
Re
peat t
he
process
unti
l al
l fr
agm
ents
assign t
o
t
he n
od
e
.
Fil
e size
s
hould be
m
or
e
than 2
0K
B
.
b.
Gen
e
ral Fl
ow
Algorithm
S = { I,
P,
R
, O
}
Wh
e
re,
I
is set
of Init
ia
l Inp
ut to
t
he
s
yst
e
m
.
I
= {i
1,
i
2,
i
3}
i1 = F
il
e
giv
e
n by the
us
e
r.
i2 =
Dow
nlo
a
d re
qu
est
from
U
ser
.
i3 =
Dow
nlo
a
d re
qu
est
from
Cl
ie
nt.
P is set
of pro
c
edure
or fu
nction o
r processe
s or m
et
ho
ds.
P = {
p1, p2,
p3, p4, p5,
p6, p
7,
p8}
p1 = Re
gistrati
on and
A
uth
e
nt
ic
at
ion
.
p2 =
Up
l
oad
i
ng a
file
on cl
oud
se
rv
e
r.
p3 = F
ra
gm
ent
at
ion
of f
il
e
with se
par
at
e
has
h key f
or each
fr
a
gm
ent r
ecei
ved f
ro
m
u
ser
.
p4 = Re
plica
tio
n o
f
t
hat f
il
e.
p5 =
Dow
nlo
a
d
Re
qu
est
fro
m
u
ser.
p6 =
Dow
nlo
a
d
Re
qu
est
f
r
om
c
li
ent.
p7 = C
ollec
ti
on
a
nd r
eas
sem
ble of
fr
a
gm
ents.
p8 =
Dow
nlo
a
ding the
origi
na
l fil
e.
R i
s a set
of
r
ules or c
onstrai
nt
s.
R=
{ r1}
r1 = Fil
e acces
sed fr
om
Replicati
on
.
O
is a
set o
f o
ut
pu
ts.
O
= {
o1 }
o1 =
Dow
nlo
a
ding the
origi
na
l fil
e.
Evaluation Warning : The document was created with Spire.PDF for Python.
Com
pu
t. Sci.
I
nf. Tec
hnol.
High sec
ur
it
y
mecha
nism: fr
agme
nta
ti
on
and re
plicati
on
in the cl
oud w
it
h
… (
Sh
r
utika
Khobr
agade
)
81
c.
Use of
Ri
jnd
ae
l Alg
or
it
hm
Ri
j
ndael
e
ncr
y
ption
al
gorit
hm
pr
opos
es
a
new
e
ncr
ypti
on
te
c
hn
i
qu
e
f
or
e
ncr
y
ption
a
nd
de
crypti
on
pur
po
se
.
It
is
a
dv
a
nce
d
AES
a
lgorit
hm
is
us
ed
to
e
nc
rypt
se
ns
it
ive
in
form
a
ti
on
.
It
is
sym
m
et
ric
key
enc
ryptio
n
al
gorithm
to
be
us
e
d
to
enc
r
yp
t
inf
or
m
at
ion
.
It
is
the
bes
t
com
bin
at
ion
of
secu
rity
,
pe
rfor
m
ance,
ef
fi
ci
ency,
easy
i
m
ple
m
en
ta
ti
on
an
d
flexi
bili
ty
,
hig
h
s
pe
ed
an
d
ve
rsati
li
ty
acro
ss
a
va
riet
y
of
platf
or
m
s.
Ru
n
eff
ic
ie
ntly
on
la
rg
e
com
pu
te
rs,
des
ktops
a
nd
sm
al
l
dev
ic
es
li
ke
sm
art
car
ds
.
T
he
bl
ock
a
nd
key
c
an
i
n
fact
be
chosen
ind
e
pende
ntly
from
12
8,
16
0,
192,
224,
256
bits.
Ri
j
ndael
is
si
m
ple
to
i
m
ple
m
ent
and
us
es
ve
r
y
li
t
tle
syst
e
m
m
e
m
or
y.
d.
Use of
S
HA
-
512 Al
gorithm
We
are
us
i
ng
SHA
-
512
Al
gorithm
fo
r
pe
rfor
m
ing
ha
s
hing
ta
sk.
S
H
A
sta
nds
f
or
"Secu
re
Has
h
Algorithm
".
Th
e
Un
it
ed
Stat
es
Nati
on
al
Se
cu
r
it
y
Ag
ency
is
de
sign
e
d
hash
i
ng
al
gorithm
.SHA
-
512
is
faster
than
SHA
-
256
on
64
-
bit
m
achines
is
that
has
le
s
s
r
ounds
per
by
te
(80
r
ounds
for
128
-
byte
blo
c
ks
)
com
par
ed
t
o
SHA
-
256
(64
r
ounds
f
or
64
by
te
blo
cks
),
H
ow
e
ve
r
,
sto
rin
g
a
S
HA
-
51
2
bit
has
h
is
ex
pe
ns
ive
.
The
S
HA
-
51
2
tim
e
to
ge
ner
at
e
the
has
h
val
ue
a
nd
the
num
ber
of
cy
cl
es
pe
r
byte
s
are
eff
ic
ie
nt
c
om
par
in
g
to
the
oth
ers
.
I
n
SHA
-
512,
the
nu
m
ber
of
cy
cl
es
pe
r
byte
s
s
om
ewh
at
m
or
e
c
om
par
ed
t
o
othe
r
h
as
hing
func
ti
on
s,
but
at
the
sam
e
tim
e
the
tim
e
t
o
ge
ner
at
e
t
he
has
hing
val
ue
is
m
uch
sm
al
l
er
tha
n
ot
her
s
.
S
o
th
e
S
H
A
-
512
has
h
f
unct
ion
is
eff
ic
ie
nt a
nd al
so
sec
ure
hash
i
ng alg
or
it
hm
.
e.
Use of
Ran
do
m
K
ey
G
ener
at
ion
Algo
rithm
Ra
ndom
Key
ge
ner
at
io
n
ge
ne
rates
rand
om
values.
It
is
use
d
for
enc
ryptio
n
a
nd
Decr
y
ption
P
urp
os
e
.
Her
e
the
Keys
are
ra
ndom
ly
gen
erate
d
us
i
ng
a
ra
ndom
num
ber
of
gen
e
rato
r
or
ps
e
udoran
do
m
num
ber
ge
ner
at
or
that
pro
duces
r
andom
data.
In
our
syst
em
Ran
dom
nu
m
ber
key
gen
e
rati
on
is
us
ed
at
t
he
t
i
m
e
of
dow
nloa
di
ng
data f
or the
us
e
r.
It m
akes m
u
ch har
der f
or a
hack
e
r or at
ta
cker t
o g
uess
t
he
k
ey
.
f.
Pr
ope
rtie
s of Pro
posed
Syste
m
Uses
t
he On
e
Ti
m
e Passwor
d Verificat
io
n schem
e.
Pr
ivacy
of d
at
a
is m
ai
ntained
from
Th
ird Par
ty
o
r
gan
iz
at
io
n.
Fil
es are
div
i
de
d
int
o fr
a
gm
e
nts a
nd sto
red
at
the v
a
rio
us l
ocati
ons.
Key g
e
ne
rati
on is do
ne
f
or eac
h fr
a
gm
ent.
Be
st encry
ptio
n
al
go
rithm
u
sed.
Ver
si
on Co
ntr
ol is
us
ed
for r
et
rievin
g old fi
le
s.
Au
t
o Update
a
nd au
t
o replic
a
te
o
f
f
il
es ar
e
done
.
Con
tr
olled
re
plica
ti
on
for
im
m
ense s
ecu
rity
.
Im
ple
m
entation
of r
eal
clo
ud.
Ther
e
are
d
i
ff
e
ren
t m
odules of syste
m
as sh
own
in Fi
gure
2
.
Th
ey
a
re as
fo
ll
ow
s:
Up
l
oad:
T
his
m
od
ule
co
ns
ist
of
uploa
ding
t
he
file
on
the
cl
oud.
Wh
e
n
t
he
file
is
uploa
ded,
a
file
i
d
i
s
gen
e
rated
for e
ach
new file
. T
hen the
nam
e to that
file
can
be give
n by the
u
se
r wh
ic
h
is
un
i
qu
e
.
Edit:
T
his
m
od
ule
is
f
or
e
diti
ng
of
the
pa
rtic
ular
fr
a
gm
ent
of
a
file
.
T
he
detai
ls
of
al
l
th
e
uploa
ded
file
s
are
show
n
in
t
hi
s
ta
ble.
Wh
e
n
any
file
is
uplo
aded
it
is
div
id
ed
int
o
var
i
ou
s
fr
a
gm
ents
an
d
encr
y
pted
and
la
te
r
st
or
e
d
in
va
rio
us
no
des.
A
nd
eac
h
fr
a
gm
ent
has
it
s
has
h
value
w
hich
is
sent
t
o
the
use
r
s
e
m
ai
l
id
durin
g
reg
ist
rati
on.
T
o
edit
we
need
to
sel
ect
any
fragm
ent
and
edi
t
that
file
,
bu
t
to
retrie
ve
that co
ntent
ha
sh
value
h
as
to
b
e e
ntere
d.
Edit
full
fi
le
:
This
m
od
ule
c
onsist
of
the
up
date
of
whole
file
.
He
re
we
c
an
up
l
oad
the
updated
file
an
d
ren
am
e the f
il
e
as
new file
. T
he old
file
is st
or
e
d
i
n
as a
b
a
ckup.
Do
w
nloa
d:
T
hi
s
m
od
ule
is
use
d
f
or
do
wn
l
oad
i
ng
the
file
wh
i
c
h
is
in
t
he
e
ncr
ypte
d
f
or
m
.
A
sin
gle
fr
a
gm
ent
can
be
dow
nlo
a
de
d
or
a
sin
gle
f
ra
gm
ent
too
.
Wh
e
n
we
dow
nlo
a
d
the
data
us
i
ng
auth
or
iz
e
d
key
it
is
fir
st
de
crypted
a
nd
t
hen
the
fr
a
gm
e
nts
a
re
com
bine
d
from
var
i
ous
nodes
use
d
a
nd
the
file
is
pr
e
sente
d i
n
it
s
or
i
gi
nal
f
or
m
.
This
is
the
proce
dure
wh
i
ch i
s
im
ple
m
ented t
o
uploa
d t
he
file
then
fr
a
gm
entat
ion
, repli
cat
ion an
d d
ownloa
d o
f o
rigin
al
file
is don
e
.
Evaluation Warning : The document was created with Spire.PDF for Python.
IS
S
N
:
2722
-
3221
Com
pu
t. Sci.
I
nf. Tec
hnol.
,
V
ol.
1
, N
o.
2
,
J
ul
y
20
20
:
78
–
83
82
Figure
2
.
Pro
pose
d
syst
em
f
l
ow
4.
RESU
LT
S
A
ND AN
ALYSIS
The
Fi
gure
3
s
hows
t
he
gap
a
naly
sis
betwee
n
e
xisti
ng
a
nd
pro
po
se
d
syst
e
m
.
The
existi
ng
syst
em
giv
es
the f
il
e to t
he
c
li
ent w
he
ne
ver request is
gran
te
d.
In t
he
e
xis
ti
ng
syst
em
ther
e w
a
s
no
t
rad
i
ti
on
al
cry
ptogr
aph
ic
te
chn
iq
ue use
d f
or
s
ecu
rity
o
f
the
data a
nd no reco
ver
y
of
da
ta
is m
a
intai
ned
.
Figure
3
.
Re
su
l
t
analy
sis
So
,
detai
ls
of
F
ig
ure
3
are
as
f
ollows:
Secu
rity
of
Fra
gm
ent:
In
the
existi
ng
syst
e
m
there
was
no
c
rypto
gr
a
phi
c
te
chn
i
que
use
d
bu
t
i
n
t
his
pro
po
se
d
syst
e
m
sp
eci
al
cryptographic
te
ch
nique
is
us
e
d
to
inc
rease
the
secu
rity
of
da
ta
for
ea
c
h
fr
a
gm
ent.
Lost
Data
Re
c
overy:
In
th
e
e
xi
sti
ng
syst
em
,
if
the
re
plica
of
a
f
rag
m
ent
is
del
et
ed,
t
her
e
was
no
recovery
syst
e
m
bu
t
i
n
this
pro
pose
d
syst
e
m
eve
n
i
f
a
ny
fr
a
gm
ent
is
delet
ed,
we
ca
n
r
et
rieve
us
i
ng
ver
si
on c
ontr
ol
.
As fr
om
the abov
e
d
et
ai
ls t
he
r
e are t
wo p
a
ra
m
et
ers
wh
ic
h d
iffer f
ro
m
the e
xisti
ng syst
em
.
Evaluation Warning : The document was created with Spire.PDF for Python.
Com
pu
t. Sci.
I
nf. Tec
hnol.
High sec
ur
it
y
mecha
nism: fr
agme
nta
ti
on
and re
plicati
on
in the cl
oud w
it
h
… (
Sh
r
utika
Khobr
agade
)
83
Table
1
.
C
om
par
iso
n of t
w
o
s
yst
e
m
s
Sr.
No.
Exis
tin
g
Sy
ste
m
Prop
o
sed
Sy
ste
m
1
On
ly
the d
ata
is se
cu
red.
Secu
rity is g
iv
en
to d
ata as we
ll
as t
r
ad
itio
n
al cr
y
p
to
g
ra
p
h
ic
tech
n
iq
u
e is us
ed
.
2
Even
if
the f
ile or f
rag
m
en
t is los
t or
wh
o
le blo
ck
is los
t,
it cann
o
t be
recov
ered.
Reco
v
ery
of
f
ile or
f
rag
m
en
t is do
n
e i
n
versio
n
con
trol.
3
Do
wn
lo
ad
of
who
l
e f
ile and
up
d
ate
is d
o
n
e.
As it is ti
m
e
con
su
m
in
g
.
Ins
tead
of
d
o
wn
lo
a
d
in
g
who
le f
ile we
can u
p
d
ate a
p
arti
cu
lar
f
rag
m
en
t on
lin
e itself
or we
can d
o
wn
lo
ad
r
eq
u
ired f
ragm
e
n
t
o
n
ly
to u
p
d
ate it.
T
h
is sav
es ti
m
e.
4
No
sep
arate
has
h
k
ey
is us
ed
f
o
r
f
rag
m
en
ts.
Sep
arate
ke
y
is
m
a
in
tain
ed
f
o
r
each f
rag
m
en
t to
m
ak
e it
m
o
re
secu
re.
5.
CONCL
US
I
O
N
A
syst
em
is
pr
opos
e
d
f
or
sec
ur
it
y
of
use
rs
’
data
wh
e
n
the
data
is
sto
red
i
n
t
he
cl
oud.
T
he
pro
pose
d
schem
e
works
for
t
he
secu
rity
of
us
e
rs’
data
wh
e
n
data
is
st
or
e
d
into
the
cl
oud.
Cl
ou
d
c
om
pu
ti
ng
gro
wth
raises
the
secu
rity
con
cer
n
du
e
t
o
it
s
cor
e
te
c
hnolo
gy
.
So
,
t
his
syst
em
pr
ovides
a
be
tt
er
so
luti
on
t
o
achie
ve
the
s
ecur
it
y
as
well
as
pe
rfor
m
ance
by
us
i
ng
te
ch
niq
ue
s
s
uch
as
secur
e
cry
ptog
raphic
sc
hem
e
,
Fra
gm
entat
ion
a
nd
Re
plica
ti
on
.
Fra
gm
entat
ion
is
us
e
d
to
pr
otect
data
f
ro
m
sing
le
point
disa
ste
r.
Re
plica
t
i
on
can
be
us
e
f
ul
f
or
m
ai
ntaining
av
ai
la
bili
ty
,
reli
abili
ty
and
perf
or
m
ance
in
fail
ur
e
sit
uatio
ns
.
But
the
e
xtra
rep
li
cat
ion
ca
n
al
so
resu
lt
in
hi
gh
s
tora
ge
c
os
t
or
dro
ps
in
syst
em
s
ov
erall
perf
or
m
ance
due
t
o
e
xtrem
e
us
e
of
ba
ndwidt
h.
So
,
he
re
con
t
ro
ll
ed
r
e
plica
ti
on
is
us
e
d.
This
sc
hem
e
util
iz
es
Ri
j
nd
ael
Algorithm
to
c
reate
an
enc
ryp
ti
on
key
that
t
he
us
e
r
gets
w
hile
requ
est
ing
to
data
owne
r
to
file
acce
ssing.
This
sc
hem
e
us
es
SHA
-
512
al
go
rith
m
fo
r
gen
e
rati
ng
has
h
key f
or each
f
r
agm
ent
after
div
isi
on.
REFE
RE
NCE
S
[1]
K.
Hashizume
,
D.
G.
Rosado,
E
.
Fern
ande
z
-
Me
dina
,
and
E
.
B
.
Ferna
ndez,
“
An
ana
l
y
sis
of
se
cur
ity
issues
for
cl
o
ud
computing
,
”
Jou
rnal
of
In
te
rnet
Serv
ices and Ap
pli
cations
,
Vol
.
4,
No.
1,
p
p.
1
-
1
3,
2013
.
[2]
D. Zissis
and D.
Le
kkas,
“
Address
ing cl
oud
comp
uti
ng
se
cur
ity
issues,”
Fut
ure
Ge
nerati
on
Comput
er
Syste
ms
,
Vol
.
28,
No.
3,
p
p.
58
3
-
592,
2012
.
[3]
M.
Hogan,
F.
L
i
u,
A.
Sokol
,
and
J.
Tong,
“
NIS
T
cl
oud
computin
g
standa
rds
roa
d
m
ap,
”
NIST
Spe
ci
al
Pub
licati
on
,
2011
.
[4]
N.
Khan
,
M.
L
.
M.
Kiah
,
S.
U.
Khan,
and
S
.
A.
Mada
n
i,
“
Towa
rds
Secur
e
Mobi
le
C
loud
Com
pu
ti
ng:
A
Surve
y
,
”
Fut
ure
Gen
eration Compute
r Sy
stems
,
Vol.
29,
No.
5,
p
p.
1278
-
1299,
2013
.
[5]
Mei,
L.
V.
Man
ci
ni
,
and
S.
Jajo
dia
,
“
Secur
e
d
y
n
amic
fr
agment
a
nd
rep
l
ica
al
lo
cation
in
la
rg
e
sc
ale
distr
ibuted
f
ile
s
y
stems
,
”
I
EEE
Tr
ansacti
ons on Paralle
l
and
Dis
tribut
ed
Syste
ms
,
Vol
.
14
,
No.
9,
p
p.
885
-
896
,
20
03.
[6]
Juels
and
A.
Opera
,
“
New Approa
che
s to
Se
cur
i
t
y
and
Avai
la
bi
lit
y
for
Cloud
Dat
a
,
”
Comm
unic
a
tions
of
ACM
,
Vo
l
.
56,
No.
2,
p
p.
64
-
73,
2013
.
[7]
G.
Kapp
es,
A.
Hatzie
l
eft
he
riou,
a
nd
S.
V.
Anastas
ia
dis,
“
Dike:
Vir
tua
liza
ti
on
-
awa
r
e
Ac
ce
ss
Con
trol
for
Mult
i
Te
n
ant
File
s
y
st
ems
,
”
U
nive
rsit
y
of
Io
an
nina
,
Gree
ce, Te
chni
c
al
R
epor
t
No.DCS
2013
-
1,
2013.
[8]
Y.
T
ang,
P.
P.
Le
e
,
J.
C.
S.
Lu
i,
and
R
.
Per
lman,
“
Secur
e
over
l
a
y
c
loud
stor
age
wi
th
acce
ss
co
ntrol
and
assured
del
e
ti
on,
”
I
EE
E
Tr
ansacti
ons on D
epe
ndable and
Sec
ure
Computi
ng
,
Vol
.
9
,
No.
6
,
p
p
.
903
-
916,
20
12.
Evaluation Warning : The document was created with Spire.PDF for Python.