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I
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er
r
ea
l
lo
ca
tio
n
o
f
th
e
u
s
er
s
.
I
f
an
a
t
tack
er
ca
n
g
et
th
e
lo
ca
tio
n
o
f
th
e
u
s
er
s
,
t
h
en
t
h
e
attac
k
er
w
il
l
d
er
iv
e
m
u
ch
p
er
s
o
n
a
l
in
f
o
r
m
atio
n
lik
e
u
s
er
’
s
h
ab
its
,
i
n
f
er
u
s
er
’
s
p
r
ese
n
t/ab
s
e
n
t
at
a
p
ar
ticu
lar
ti
m
e
w
it
h
p
lace
an
d
m
a
n
y
o
t
h
er
in
f
o
r
m
atio
n
wh
ich
i
s
h
ig
h
l
y
p
er
s
o
n
alize
d
.
2)
P
ee
r
-
to
-
p
ee
r
m
o
d
el
An
o
p
tio
n
al
m
o
d
el
i
s
th
e
p
ee
r
-
to
-
p
ee
r
m
o
d
el
w
h
er
e
th
e
u
s
er
s
o
f
ea
ch
n
o
d
e
w
o
u
ld
li
k
e
to
co
m
m
u
n
icat
e
w
it
h
ea
ch
o
t
h
er
w
i
th
o
u
t
s
ee
k
i
n
g
t
h
e
h
elp
o
f
a
n
y
o
t
h
er
ce
n
tr
alize
n
o
d
e/
s
er
v
er
to
co
m
p
u
te
th
e
tas
k
s
.
T
h
is
d
is
tr
ib
u
ted
m
o
d
el
w
id
el
y
u
s
ed
to
co
m
p
u
te
an
y
ta
s
k
to
g
eth
er
w
i
th
o
u
t
th
e
h
elp
o
f
o
u
ts
id
er
s
.
A
ll
u
s
er
s
h
av
e
to
tr
u
s
t
o
n
ea
ch
o
th
er
an
d
also
p
er
f
o
r
m
th
is
tas
k
in
a
s
ec
u
r
e
m
a
n
n
er
.
Fi
g
u
r
e
1
s
h
o
w
th
e
co
m
m
u
n
ica
tio
n
s
c
h
e
m
a
b
et
w
ee
n
a
s
et
o
f
co
llab
o
r
ativ
e
u
s
er
s
an
d
L
B
S p
r
o
v
id
er
.
Fig
u
r
e
1
.
C
o
m
m
u
n
icatio
n
s
c
h
e
m
a
b
et
w
ee
n
a
s
e
t o
f
co
llab
o
r
ativ
e
u
s
er
s
a
n
d
L
B
S p
r
o
v
id
er
[
2
]
3)
T
T
P
f
r
ee
co
llab
o
r
ativ
e
-
b
ased
s
ch
e
m
a
Fig
u
r
e
2
s
h
o
w
s
th
e
co
llab
o
r
ati
v
e
m
e
th
o
d
b
et
w
ee
n
t
w
o
u
s
er
s
.
T
h
is
s
ch
e
m
a
i
s
f
u
ll
y
d
is
tr
ib
u
te
d
s
ch
e
m
a.
T
h
e
tr
u
s
t
is
s
ca
tter
ed
a
m
o
n
g
t
h
e
n
o
d
es
th
at
f
o
r
m
s
an
ad
-
h
o
c
n
et
w
o
r
k
.
A
ll
p
ee
r
s
w
o
r
k
co
llab
o
r
ativ
el
y
to
ac
h
ie
v
e
p
r
iv
ac
y
a
m
o
n
g
u
n
tr
u
s
ted
en
ti
t
ies.
Var
io
u
s
alg
o
r
it
h
m
s
ar
e
al
r
ea
d
y
p
r
o
p
o
s
ed
as
So
lan
a
s
&
B
alleste,
R
eb
o
ll
o
-
Mo
n
ed
er
o
,
A
r
d
ag
n
a
etal,
E
tc
[
3
-
9
]
.
T
h
e
a
d
v
an
ta
g
e
o
f
th
is
ap
p
r
o
ac
h
i
s
th
at
it
d
o
es
n
o
t
r
ely
o
n
T
T
P
,
it
is
d
is
tr
ib
u
ted
an
d
also
g
u
a
r
an
tees
u
s
er
’
s
p
r
iv
ac
y
.
T
h
e
m
ai
n
d
is
ad
v
a
n
ta
g
e
o
f
th
i
s
m
eth
o
d
is
r
elate
d
to
th
e
C
o
m
p
u
tat
io
n
&
C
o
m
m
u
n
i
ca
tio
n
co
s
t a
n
d
Scalab
ilit
y
i
s
s
u
es.
Fig
u
r
e
2.
T
h
e
co
m
m
u
n
icatio
n
s
ch
e
m
a
o
f
C
o
llab
o
r
ativ
e
Me
th
o
d
b
etw
ee
n
User
s
,
L
B
S P
r
o
v
id
er
[
2
]
Evaluation Warning : The document was created with Spire.PDF for Python.
I
SS
N
:
2
0
8
8
-
8708
I
n
t J
E
lec
&
C
o
m
p
E
n
g
,
Vo
l.
9
,
No
.
6
,
Dec
em
b
er
2
0
1
9
:
5
3
7
6
-
5
3
8
5
5378
4)
Den
s
i
t
y
b
ased
clu
s
ter
i
n
g
al
g
o
r
ith
m
s
Den
s
i
t
y
b
ased
cl
u
s
ter
in
g
al
g
o
r
ith
m
s
is
a
p
r
o
ce
s
s
o
f
m
a
k
in
g
th
e
g
r
o
u
p
o
f
o
b
j
ec
ts
w
h
ic
h
s
h
ar
e
th
e
co
m
m
o
n
p
r
o
p
er
ty
ca
lled
as
clu
s
ter
i
n
g
.
I
t
p
r
o
v
id
es
th
e
b
en
ef
it
to
f
in
d
o
u
t
d
if
f
er
en
t
g
r
o
u
p
s
b
ased
o
n
th
eir
p
r
o
p
er
ties
.
A
clu
s
ter
in
g
tec
h
n
i
q
u
e
w
id
el
y
u
s
ed
i
n
v
ar
io
u
s
ap
p
licatio
n
s
lik
e
Data
Mi
n
i
n
g
,
T
ex
t
Mi
n
i
n
g
,
L
o
ca
tio
n
B
ased
Ser
v
ices,
I
m
a
g
e
P
r
o
ce
s
s
in
g
,
W
eb
Min
i
n
g
a
n
d
m
a
n
y
m
o
r
e.
I
t
is
th
e
p
r
o
ce
s
s
o
f
m
ak
in
g
th
e
g
r
o
u
p
s
o
f
p
o
in
ts
to
g
et
h
er
,
w
h
ich
ar
e
clo
s
e
to
th
e
g
i
v
en
d
at
aset/s
et
o
f
p
o
in
ts
in
s
p
ac
e.
T
h
is
is
k
n
o
w
n
as
d
en
s
it
y
b
ased
clu
s
ter
i
n
g
.
E
x
a
m
p
le
o
f
d
en
s
i
t
y
b
ased
cl
u
s
t
er
in
g
ar
e
DB
SC
AN
&
OP
T
I
C
S
[
10
,
1
1
]
.
I
n
DB
s
ca
n
[
10
,
1
1
]
alg
o
r
ith
m
,
clu
s
ter
o
f
th
e
d
ata
o
b
j
ec
t
is
g
en
er
ated
b
as
ed
o
n
th
eir
d
en
s
it
y
.
DB
s
ca
n
is
p
o
p
u
lar
alg
o
r
it
h
m
an
d
w
i
ld
l
y
u
s
e
to
f
i
n
d
n
o
n
-
s
p
h
er
ical
s
h
ap
e
clu
s
ter
i
n
g
f
r
o
m
th
e
g
i
v
e
n
d
ataset.
DB
s
ca
n
is
q
u
ite
f
a
s
ter
f
o
r
p
r
o
ce
s
s
in
g
&
w
id
el
y
s
u
i
ta
b
le
f
o
r
n
o
n
-
c
h
a
n
g
ea
b
le
d
en
s
it
y
b
ased
o
b
j
ec
ts
.
Op
tics
[
10
,
1
1
]
u
s
es
t
h
e
co
n
c
ep
t
o
f
id
en
t
if
icatio
n
o
f
t
h
e
i
m
p
licit
clu
s
ter
i
n
g
f
o
r
g
iv
e
n
s
et
o
f
p
o
in
t
i
n
d
ata
s
et.
I
t
cr
ea
tes
an
o
r
d
er
in
g
o
f
th
e
d
ata
s
et
o
b
j
ec
ts
an
d
also
s
to
r
e
t
h
e
d
is
tan
ce
s
an
d
r
ea
ch
ab
ilit
y
t
o
o
th
er
n
o
d
es
w
it
h
d
is
tan
ce
.
5)
Ho
m
o
m
o
r
p
h
ic
e
n
cr
y
p
tio
n
Ho
m
o
m
o
r
p
h
ic
e
n
cr
y
p
tio
n
i
s
a
s
ch
e
m
a
w
h
ic
h
p
er
f
o
r
m
s
th
e
v
ar
io
u
s
co
m
p
u
tatio
n
s
o
n
e
n
cr
y
p
ted
d
ata
.
Ho
m
o
m
o
r
p
h
ic
en
cr
y
p
tio
n
tech
n
iq
u
e
is
w
id
el
y
u
s
ed
to
p
r
es
er
v
e
p
r
iv
ac
y
an
d
s
ec
u
r
it
y
i
n
v
ar
io
u
s
ar
ea
.
P
r
iv
ac
y
h
o
m
o
m
o
r
p
h
is
m
w
il
l p
r
o
v
id
e
a
g
u
ar
a
n
tee
o
f
lo
ca
tio
n
p
r
iv
ac
y
o
f
th
e
u
s
er
s
[
1
2
-
17
]
.
P
r
iv
ac
y
h
o
m
o
m
o
r
p
h
is
m
h
as
b
o
th
t
y
p
es o
f
f
u
n
ct
io
n
: E
n
cr
y
p
tio
n
an
d
Dec
r
y
p
tio
n
.
W
ith
th
e
u
s
e
o
f
Ho
m
o
m
o
r
p
h
ic
en
cr
y
p
ti
o
n
,
u
s
er
is
n
o
t a
b
le
to
s
ee
th
e
ac
tu
a
l lo
ca
tio
n
o
f
t
h
e
co
m
p
a
n
io
n
.
6)
R
an
d
o
m
c
h
ai
n
i
n
g
Du
e
to
co
llis
io
n
p
r
o
b
le
m
,
p
r
iv
ac
y
h
o
m
o
m
o
r
p
h
is
m
i
s
n
o
t
m
u
ch
s
ec
u
r
e.
T
o
av
o
id
th
is
p
r
o
b
le
m
,
r
an
d
o
m
ch
ain
in
g
is
o
n
e
o
f
th
e
b
est
a
p
p
r
o
ac
h
[
1
3
]
.
I
n
th
is
m
et
h
o
d
,
u
s
er
s
w
il
l
r
an
d
o
m
l
y
s
elec
t
t
h
e
co
m
p
an
io
n
f
r
o
m
in
ter
ested
u
s
er
s
.
T
h
e
m
ai
n
g
o
al
b
eh
in
d
t
h
e
r
an
d
o
m
ch
a
in
in
g
is
to
av
o
id
s
e
n
d
in
g
m
e
s
s
ag
es
to
t
h
e
ce
n
tr
al
co
llecto
r
/
m
ain
a
g
g
r
eg
ato
r
n
o
d
e.
T
h
is
ap
p
r
o
ac
h
w
i
ll
also
p
r
o
v
id
e
m
o
r
e
s
ec
u
r
it
y
ag
ai
n
s
t
co
llu
s
io
n
attac
k
in
d
is
tr
ib
u
ted
co
m
p
u
tat
io
n
o
f
t
h
e
s
u
m
o
f
t
h
e
lo
ca
tio
n
.
b)
T
h
e
p
r
o
b
lem
s
tate
m
en
t
L
o
ca
tio
n
p
r
iv
ac
y
i
s
o
n
e
o
f
th
e
k
e
y
is
s
u
es
th
at
n
ee
d
s
to
b
e
s
o
l
v
ed
.
T
h
er
e
ar
e
v
ar
io
u
s
s
c
h
e
m
a
s
p
r
o
p
o
s
ed
b
y
d
if
f
er
e
n
t
r
esear
ch
er
s
[
8
,
9
,
1
8
-
2
3
]
.
Ou
t
o
f
th
at
C
o
llab
o
r
ativ
e
T
T
P
Fre
e
m
o
d
el
[
2
4
-
2
6
]
is
o
n
e
o
f
th
e
b
est
tech
n
iq
u
e
to
p
r
o
v
id
e
h
ig
h
es
t
l
o
ca
tio
n
p
r
iv
ac
y
.
T
h
o
u
g
h
s
c
h
e
m
as
[
2
4
-
2
6
]
h
av
e
t
h
e
ad
v
a
n
ta
g
es,
t
h
er
e
ar
e
s
till
o
p
en
is
s
u
es
t
h
at
r
eq
u
ir
e
atten
ti
o
n
.
L
o
ca
tio
n
b
ased
s
er
v
ices
ar
e
g
ain
i
n
g
p
o
p
u
lar
it
y
d
u
e
to
t
h
e
in
cr
ea
s
e
in
lo
ca
tio
n
b
ased
in
f
o
r
m
atio
n
r
eq
u
ir
ed
b
y
th
e
u
s
er
s
.
He
n
ce
co
s
t
an
d
th
e
s
ca
lab
ilit
y
o
f
t
h
e
s
y
s
te
m
i
s
th
e
m
o
s
t
ch
alle
n
g
in
g
is
s
u
e
n
ee
d
to
b
e
f
o
cu
s
ed
.
So
,
th
er
e
is
a
n
ee
d
o
f
an
ap
p
r
o
ac
h
th
at
p
r
o
v
id
es
lo
w
er
co
m
m
u
n
icatio
n
a
n
d
co
m
p
u
tatio
n
al
co
s
t,
i
m
p
r
o
v
es
s
ca
lab
ilit
y
al
s
o
p
r
o
v
id
es
p
r
iv
ac
y
th
at
is
n
o
t
d
o
n
e
till
n
o
w
.
H
en
ce
,
in
th
i
s
s
ec
tio
n
w
e
p
r
o
p
o
s
e
th
e
p
r
iv
ac
y
p
r
eser
v
in
g
L
B
S
s
c
h
e
m
a
th
a
t
is
T
T
P
f
r
ee
,
i
m
p
r
o
v
es
s
ca
lab
ilit
y
,
lo
w
er
co
s
t,
r
o
b
u
s
t
ag
ai
n
s
t
th
e
co
llis
io
n
o
f
u
s
er
s
a
n
d
also
p
r
o
v
id
es p
r
iv
ac
y
.
2.
P
RAP
O
SE
D
AP
P
RO
ACH
I
n
th
is
s
ec
tio
n
,
w
e
p
r
o
p
o
s
e
a
n
o
v
el
s
o
lu
tio
n
th
at
p
r
o
v
id
es
lo
ca
tio
n
p
r
iv
ac
y
t
o
th
e
L
B
S
u
s
er
s
.
T
h
e
m
ain
g
o
al
o
f
r
esear
ch
is
t
o
ac
h
iev
e
f
ea
t
u
r
es
th
at
d
o
es
n
o
t
r
el
y
o
n
T
T
P
an
d
r
an
d
o
m
ize
ap
p
r
o
ac
h
an
d
also
i
m
p
r
o
v
es
s
ca
lab
ilit
y
,
r
ed
u
ce
co
s
t
in
r
eso
u
r
ce
co
n
s
tr
ai
n
t
d
e
v
ices,
a
n
d
en
h
an
ce
s
ec
u
r
it
y
&
p
r
iv
ac
y
.
Fi
g
u
r
e
3
r
ep
r
esen
ts
th
e
s
y
s
te
m
ar
c
h
itect
u
r
e
o
f
p
r
o
p
o
s
ed
s
ch
em
a
[
2
7
]
.
I
t c
o
n
tain
s
t
w
o
m
ai
n
co
m
p
o
n
e
n
ts
as a
)
L
B
S u
s
er
s
an
d
b
)
L
B
S
p
r
o
v
id
er
.
E
ac
h
u
s
er
h
a
s
th
eir
p
r
iv
ate
in
f
o
r
m
atio
n
o
n
th
eir
m
o
b
ile
li
k
e
User
I
D
Uid
,
lo
ca
tio
n
in
f
o
r
m
atio
n
(
L
g
i,
L
ti).
I
n
o
u
r
ap
p
r
o
ac
h
,
o
u
r
p
r
im
ar
y
f
o
c
u
s
i
s
to
f
in
d
o
u
t
th
e
n
u
m
b
er
o
f
User
s
Ui
in
clo
ak
i
n
g
r
eg
io
n
w
h
o
ar
e
r
eq
u
esti
n
g
f
o
r
lo
ca
tio
n
-
b
as
ed
in
f
o
r
m
atio
n
.
As
s
h
o
w
n
in
Fi
g
u
r
e
3
,
w
e
ar
e
g
en
er
ati
n
g
r
an
d
o
m
r
eg
io
n
[
28
,
29
]
R
i
b
ased
o
n
t
h
e
d
en
s
it
y
b
ased
cl
u
s
ter
i
n
g
al
g
o
r
ith
m
o
p
tics
[
10
,
1
1
]
an
d
Db
s
ca
n
[
10
,
1
1
]
f
o
r
u
s
er
s
in
s
p
atial
clo
ak
e
d
r
eg
io
n
.
T
h
en
all
u
s
er
s
w
ill
ad
d
r
an
d
o
m
n
o
is
e
b
y
u
s
i
n
g
th
e
s
ec
r
et
s
h
ar
e
f
u
n
ctio
n
.
A
f
ter
t
h
is
,
w
e
u
s
e
d
ec
en
tr
alize
ap
p
r
o
ac
h
to
p
er
f
o
r
m
s
ec
u
r
e
d
ata
ag
g
r
eg
atio
n
u
s
i
n
g
p
r
iv
ac
y
h
o
m
o
m
o
r
p
h
is
m
P
H
[
1
3
]
in
ea
ch
r
an
d
o
m
r
e
g
io
n
R
i
u
s
i
n
g
r
an
d
o
m
ch
ai
n
i
n
g
th
at
is
s
h
o
w
n
i
n
Fi
g
u
r
e
3
w
it
h
r
ed
ed
g
es.
T
h
en
,
w
e
u
s
ed
th
e
d
ec
en
tr
alize
d
ap
p
r
o
ac
h
to
p
er
f
o
r
m
r
a
n
d
o
m
c
h
ain
in
g
R
C
f
o
r
all
d
is
tr
ib
u
ted
r
an
d
o
m
r
e
g
io
n
R
i
to
co
m
p
u
te
th
e
s
e
c
u
r
e
ce
n
tr
o
id
C
as
s
h
o
wn
in
Fi
g
u
r
e
3
w
it
h
g
r
ee
n
ed
g
e
s
.
Af
ter
th
i
s
,
th
e
las
t
u
s
er
,
U
s
en
d
s
th
e
e
n
cr
y
p
ted
s
u
m
o
f
lo
ca
tio
n
C
to
L
B
S p
r
o
v
id
er
P
as sh
o
w
n
i
n
Fi
g
u
r
e
3
w
it
h
b
lack
ed
g
e.
T
h
e
m
ain
ai
m
o
f
o
u
r
ap
p
r
o
ac
h
i
s
to
h
id
e
t
h
e
u
s
er
’
s
lo
ca
t
io
n
f
r
o
m
t
h
e
o
t
h
er
u
s
er
s
a
n
d
also
g
iv
e
in
ac
cu
r
ate
lo
ca
tio
n
i
n
f
o
r
m
a
tio
n
to
th
e
L
B
S p
r
o
v
id
er
.
Ou
r
ap
p
r
o
ac
h
is
b
ased
o
n
d
ec
en
tr
al
ize
ap
p
r
o
ac
h
,
th
at
u
s
e
d
is
tr
ib
u
ted
m
et
h
o
d
to
ac
h
iev
e
m
i
n
i
m
u
m
co
s
t
an
d
s
ca
lab
ilit
y
.
I
n
th
is
p
ap
er
,
w
e
p
r
o
p
o
s
e
a
p
r
o
to
co
l
s
ch
em
a
f
o
r
p
r
iv
ac
y
p
r
eser
v
atio
n
b
et
w
ee
n
u
s
er
s
a
n
d
L
B
S p
r
o
v
id
er
.
Evaluation Warning : The document was created with Spire.PDF for Python.
I
n
t J
E
lec
&
C
o
m
p
E
n
g
I
SS
N:
2
0
8
8
-
8708
Dec
en
tr
a
liz
ed
co
lla
b
o
r
a
tive
TT
P
fr
ee
a
p
p
r
o
a
ch
fo
r
p
r
iva
cy
p
r
eser
v
a
tio
n
in
lo
ca
tio
n
...
(
A
ja
ysin
h
R
a
th
o
d
)
5379
Fig
u
r
e
3.
P
r
o
p
o
s
ed
c
o
m
m
u
n
ic
atio
n
s
c
h
e
m
a
o
f
d
ec
en
tr
alize
d
m
et
h
o
d
b
et
w
ee
n
u
s
er
s
,
L
B
S
p
r
o
v
id
er
a)
P
r
o
p
o
s
ed
P
r
o
to
c
o
l Sch
e
m
a
Ou
r
p
r
o
p
o
s
ed
p
r
o
to
c
o
l sch
e
m
a
d
iv
id
ed
in
5
p
h
ase
as f
o
llo
ws:
1)
P
h
ase
-
1
C
r
ea
te
R
an
d
o
m
R
eg
i
o
n
in
t
h
e
clo
ak
ed
r
eg
io
n
N
User
s
n
ee
d
i
m
p
o
r
tan
t
in
f
o
r
m
a
tio
n
b
ased
o
n
t
h
eir
lo
ca
tio
n
.
An
i
n
itiato
r
w
ill
s
e
n
d
th
e
m
e
s
s
a
g
e
to
all
th
e
u
s
er
s
i
n
th
e
clo
ak
ed
r
eg
io
n
till
K
n
o
.
o
f
u
s
er
s
w
ill
r
esp
o
n
d
h
i
m
/h
er
.
A
n
y
o
n
e
u
s
er
w
ill
ca
ll
R
an
d
o
m
R
eg
io
n
(
)
to
cr
ea
te
s
u
b
-
r
eg
io
n
b
y
u
s
in
g
d
en
s
it
y
b
ased
clu
s
ter
in
g
alg
o
r
ith
m
s
.
B
y
en
d
o
f
th
is
p
h
a
s
e,
d
if
f
er
en
t
s
u
b
r
eg
io
n
s
ar
e
cr
ea
ted
.
2)
P
h
ase
-
2
A
ll
u
s
er
s
ad
d
r
an
d
o
m
n
o
is
e
i
n
th
eir
c
u
r
r
en
t lo
ca
tio
n
I
n
th
is
p
h
ase,
ea
ch
u
s
er
w
ill
a
d
d
r
an
d
o
m
n
o
i
s
e
o
n
th
eir
ac
t
u
al
lo
ca
tio
n
b
y
u
s
i
n
g
Secr
e
t_
Sh
ar
e
(
)
.
A
ll
u
s
er
s
w
ill
ad
d
r
an
d
o
m
n
o
is
e
(
,
)
=
(
(
+
)
,
(
+
)
)
.
I
n
ea
ch
r
a
n
d
o
m
r
eg
io
n
,
th
e
u
s
er
s
elec
t
s
an
y
u
s
er
as a
g
g
r
e
g
ato
r
ex
ec
u
t
o
r
A
E
to
p
er
f
o
r
m
t
h
e
n
e
x
t c
o
m
p
u
tat
io
n
w
h
er
e
A
E
∈
.
3)
P
h
ase
-
3
P
er
f
o
r
m
Sec
u
r
e
Data
A
g
g
r
eg
a
tio
n
u
s
i
n
g
p
r
iv
ac
y
h
o
m
o
m
o
r
p
h
is
m
(
-
P
H)
u
s
i
n
g
r
an
d
o
m
ch
ai
n
i
n
g
m
et
h
o
d
in
ea
ch
r
an
d
o
m
r
e
g
io
n
I
n
ea
ch
r
an
d
o
m
r
eg
io
n
,
ag
g
r
e
g
ato
r
ex
ec
u
to
r
A
E
w
ill
p
er
f
o
r
m
s
ec
u
r
e
d
ata
ag
g
r
eg
a
tio
n
u
s
i
n
g
p
r
iv
ac
y
h
o
m
o
m
o
r
p
h
is
m
P
H.
A
ll
u
s
er
s
w
ill
ca
l
l
Secu
r
e_
Data
_
Ag
g
r
e
g
atio
n
(
)
to
p
er
f
o
r
m
co
m
p
u
tati
o
n
.
Her
e,
b
y
u
s
i
n
g
d
ec
en
tr
alize
ap
p
r
o
ac
h
,
th
e
u
s
e
r
w
ill
s
elec
t
a
r
an
d
o
m
u
s
er
u
s
i
n
g
R
a
n
d
o
m
_
R
e
g
io
n
(
)
f
r
o
m
e
ac
h
r
an
d
o
m
r
e
g
io
n
to
av
o
id
co
llis
io
n
attac
k
.
Af
te
r
th
e
en
d
o
f
th
is
p
h
ase,
all
A
E
w
ill
h
a
v
e
s
ec
u
r
e
s
u
m
o
f
t
h
eir
r
an
d
o
m
r
eg
io
n
(
(
∑
(
)
)
=
1
,
(
∑
(
)
)
=
1
).
4)
P
h
ase
-
4
I
m
p
le
m
e
n
t
d
ec
en
tr
ali
ze
R
an
d
o
m
C
h
a
in
i
n
g
(
R
C
)
f
o
r
all
r
an
d
o
m
r
eg
io
n
r
i
an
d
co
m
p
u
te
t
h
e
s
ec
u
r
e
ce
n
tr
o
id
C
f
o
r
clo
ak
ed
ar
ea
I
n
th
i
s
p
h
ase,
User
U
w
il
l
s
ele
ct
a
r
an
d
o
m
A
E
f
r
o
m
ea
ch
r
e
g
io
n
an
d
p
er
f
o
r
m
s
ec
u
r
e
s
u
m
f
o
r
ea
ch
r
an
d
o
m
r
eg
io
n
.
L
ast
u
s
er
w
ill
co
m
p
u
te
s
ec
u
r
e
ce
n
tr
o
id
(
(
∑
(
)
)
=
1
,
(
∑
(
)
)
=
1
)
.
L
ast
u
s
er
w
ill
s
en
d
s
ec
u
r
e
ce
n
tr
o
id
C
to
th
e
L
B
S
p
r
o
v
id
er
P.
5)
P
h
ase
-
5
L
B
S P
r
o
v
id
er
P p
er
f
o
r
m
s
d
ec
r
y
p
tio
n
o
n
e
n
cr
y
p
ted
s
u
m
C
an
d
Fi
n
d
C
e
n
tr
o
id
.
Fin
all
y
,
L
o
ca
tio
n
b
ased
s
er
v
ices
(
L
B
S)
p
r
o
v
id
er
P
d
ec
r
y
p
ti
n
g
s
ec
u
r
e
ce
n
tr
o
id
(
(
∑
(
)
)
=
1
,
(
∑
(
)
)
=
1
)
u
s
in
g
h
is
/h
er
p
r
iv
ate
k
e
y
.
T
h
e
p
r
o
v
id
er
w
ill
o
b
tain
th
e
v
alu
e
(
∑
(
)
=
1
,
∑
(
)
)
=
1
.
L
as
t,
P
r
o
v
id
er
P
w
ill d
i
v
i
d
e
it b
y
K
&
f
i
n
d
ce
n
tr
o
id
C
.
C
o
n
s
id
er
atio
n
s
an
d
Ass
u
m
p
t
io
n
s
:
i.
Usi
n
g
P
u
b
lic
k
e
y
i
n
f
r
astr
u
ctu
r
e
(
P
KI
)
,
User
w
ill
g
et
th
e
p
u
b
lic
k
e
y
o
f
L
B
S
p
r
o
v
id
er
f
r
o
m
d
ir
ec
to
r
y
/
a
u
th
o
r
it
y
.
ii.
Mo
b
ile
u
s
er
h
a
v
e
to
en
ab
le
lo
ca
tio
n
b
ased
s
er
v
ices to
g
et
h
i
s
/h
er
lo
ca
tio
n
i
n
f
o
r
m
ati
o
n
.
Evaluation Warning : The document was created with Spire.PDF for Python.
I
SS
N
:
2
0
8
8
-
8708
I
n
t J
E
lec
&
C
o
m
p
E
n
g
,
Vo
l.
9
,
No
.
6
,
Dec
em
b
er
2
0
1
9
:
5
3
7
6
-
5
3
8
5
5380
b)
P
r
o
p
o
s
ed
A
lg
o
r
ith
m
s
Alg
o
rit
h
m
1
: U
s
er
s
co
m
m
u
n
i
ca
te
u
s
i
n
g
P
r
o
p
o
s
ed
Mo
d
el
I
np
ut
:
L
B
S U
s
er
s
(
User
I
d
en
tif
icat
io
n
,
P
o
s
itio
n
in
f
o
r
m
a
tio
n
(
,
)
)
O
utput
: Co
m
p
u
te
Sec
u
r
e
C
e
n
tr
o
id
C
.
1
-
User
s
tar
ts
a
n
d
s
en
d
q
u
er
y
to
P
r
o
v
id
er
P
&
N
r
ep
r
esen
ts
th
e
m
i
n
i
m
u
m
n
u
m
b
er
o
f
u
s
er
r
eq
u
ir
e
to
cr
ea
te
ce
n
tr
o
id
C
;
2
-
L
et
K
i
s
th
e
n
o
.
o
f
in
ter
e
s
te
d
u
s
er
w
h
o
r
esp
o
n
d
ed
,
m
is
t
h
e
n
o
.
o
f
u
s
er
s
i
n
r
an
d
o
m
r
e
g
io
n
,
is
a
r
an
d
o
m
r
eg
io
n
w
h
er
e
i=1
t
o
N;
3
-
Star
t,
C
=0
,
i=0
,
k
=0
;
4
-
L
et
s
ea
ch
u
s
er
s
ar
e
h
av
i
n
g
t
h
eir
lo
ca
tio
n
i
n
f
o
r
m
atio
n
as
(
,
)
;
//
P
ha
s
e
-
1
Cre
a
t
e
Ra
nd
o
m
R
eg
io
n in c
lo
a
k
ed
re
g
io
n
5
-
Mo
b
ile
u
s
er
C
AL
L
R
a
n
d
o
m
_
R
e
g
io
n
_
F
u
n
ctio
n
;
6
-
F
o
r
ea
ch
r
an
d
o
m
r
eg
io
n
do
F
o
r
j FR
OM
1
T
O
clu
s
ter
.
s
ize
do
//Pha
s
e
-
2
All us
er
s
a
d
d r
a
nd
o
m
no
i
s
e
in t
heir
curr
ent
lo
c
a
t
io
n
C
all
Secr
et_
S
h
ar
e_
Fu
n
ctio
n
;
(
,
)
=
(
(
+
)
,
(
+
)
)
;
User
U,
s
elec
t a
r
an
d
o
m
n
o
d
e
as a
g
g
r
eg
ato
r
ex
ec
u
to
r
A
E
,
AE
∈
;
//Pha
s
e
-
3
P
er
f
o
r
m
Secure
D
a
t
a
Ag
g
re
g
a
t
i
o
n us
ing
priv
a
cy
ho
m
o
m
o
rph
is
m
P
H
u
s
ing
ra
nd
o
m
cha
i
nin
g
m
et
ho
d in e
a
ch
ra
nd
o
m
re
g
i
o
n
P
er
f
o
r
m
s
ec
u
r
e
s
u
m
w
it
h
in
r
e
g
io
n
R
i,
C
all
Sec
u
r
e_
Data
_
A
g
g
r
eg
atio
n
;
(
(
∑
(
)
)
=
1
,
(
∑
(
)
)
=
1
));
E
nd
f
o
r
E
nd
f
o
r
//Pha
s
e
4
-
I
m
ple
m
e
nt
dece
n
t
ra
lize
Ra
nd
o
m
C
ha
ini
ng
R
C
f
o
r
a
ll r
a
nd
o
m
re
g
io
n
a
nd
co
m
p
ute
t
he
s
ec
ure
ce
ntr
o
id
C
f
o
r
clo
a
k
ed
a
re
a
.
7
-
F
o
rEa
ch
r
an
d
o
m
r
eg
io
n
do
User
U,
s
elec
t a
r
an
d
o
m
A
E
f
r
o
m
ea
c
h
r
eg
io
n
;
P
er
f
o
r
m
s
ec
u
r
e
s
u
m
a
n
d
f
i
n
d
s
ec
u
r
e
ce
n
tr
o
id
(
(
∑
(
)
)
=
1
,
(
∑
(
)
)
=
1
);
8
-
E
n
d f
o
r
9
-
L
a
s
t
A
E
s
e
n
d
en
cr
y
p
ted
r
es
u
lt C
e
n
tr
o
id
(
∑
(
)
)
=
1
,
(
∑
(
)
)
=
1
)
)
to
p
r
o
v
id
er
;
// P
ha
s
e
5
:
L
B
S P
ro
v
ider
P
perf
o
r
m
decr
y
ptio
n o
n e
ncry
pte
d su
m
C
a
nd
F
ind
Ce
ntr
o
id.
10
-
P
r
o
v
id
er
P
d
ec
r
y
p
t t
h
e
s
u
m
o
f
lo
ca
tio
n
b
y
ap
p
l
y
in
g
h
is
/
h
er
p
r
iv
ate
k
e
y
.
Alg
o
rit
h
m
2
: Ra
n
d
o
m
_
R
eg
io
n
_
Fu
n
ctio
n
I
np
ut:
User
s
,
Min
P
ts
,
R
ad
i
u
s
.
O
utput
:
Ne
w
C
l
u
s
ter
s
.
1
-
L
et
s
Set M
i
n
P
ts
=2
,
E
p
s
=0
.
0
0
5
;
2
-
A
p
p
l
y
Den
s
it
y
b
ased
clu
s
te
r
in
g
al
g
o
r
ith
m
s
;
3
-
F
o
r
(
ea
ch
u
s
er
K)
do
4
-
Fo
r
m
ed
clu
s
ter
;
5
-
E
n
d f
o
r
6
-
R
et
u
r
n
;
Alg
o
rit
h
m
3
: Sec
r
et_
S
h
ar
e_
F
u
n
ct
io
n
1
-
A
E
s
elec
t a
n
d
d
iv
id
e
lar
g
e
r
an
d
o
m
s
h
ar
es S
f
o
r
u
s
er
s
s
u
c
h
th
at
∑
=
0
1
;
2
-
A
E
s
e
n
d
all
s
ec
r
et
s
h
ar
e
v
a
lu
e
to
all
u
s
er
s
ϵ
;
Evaluation Warning : The document was created with Spire.PDF for Python.
I
n
t J
E
lec
&
C
o
m
p
E
n
g
I
SS
N:
2
0
8
8
-
8708
Dec
en
tr
a
liz
ed
co
lla
b
o
r
a
tive
TT
P
fr
ee
a
p
p
r
o
a
ch
fo
r
p
r
iva
cy
p
r
eser
v
a
tio
n
in
lo
ca
tio
n
...
(
A
ja
ysin
h
R
a
th
o
d
)
5381
Alg
o
rit
h
m
4
: Ra
n
d
o
m
C
h
ai
n
ap
p
r
o
ac
h
I
np
ut:
User
s
,
Min
P
ts
,
R
ad
i
u
s
.
O
utput
:
Select
R
a
n
d
o
m
C
o
m
p
an
io
n
.
1
-
User
u
b
u
i
ld
ch
ai
n
C
b
y
id
e
n
ti
f
y
in
g
n
o
o
f
u
s
er
s
;
2
-
Whil
e
r
s
≠
E
m
p
t
y
do
3
-
User
u
r
an
d
o
m
l
y
s
e
lect
co
m
p
a
n
io
n
;
4
-
Dele
te
s
elec
ted
co
m
p
an
io
n
f
r
o
m
lis
t;
5
-
E
n
d do
6
-
R
et
u
r
n
r
an
d
o
m
_
co
m
p
a
n
io
n
;
Alg
o
rit
h
m
5
: Sec
u
r
e
Data
A
g
g
r
eg
atio
n
I
np
ut:
User
s
,
L
o
ca
tio
n
i
n
f
o
,
P
u
b
lic
k
e
y
o
f
P
r
o
v
id
er
s
O
utput
:
E
n
cr
y
p
ted
Su
m
o
f
L
o
ca
tio
n
.
1
-
C
all
R
an
d
o
m
_
C
h
ai
n
i
n
g
;
2
-
A
p
p
l
y
Ho
m
o
m
o
r
p
h
ic
E
n
cr
y
p
tio
n
A
l
g
o
r
it
h
m
s
;
3
-
R
et
u
r
n
E
n
cr
y
p
ted
C
e
n
tr
o
id
;
3.
RE
SU
L
T
S
A
ND
AN
AL
Y
SI
S
W
e
h
av
e
i
m
p
le
m
e
n
ted
an
d
ex
p
er
im
e
n
ted
o
u
r
p
r
o
p
o
s
ed
a
p
p
r
o
ac
h
i
n
J
av
a.
W
e
r
u
n
it
o
n
an
I
n
tel
C
o
r
e
i3
2
.
3
0
GHz
m
ac
h
in
e
w
i
th
2
GB
o
f
R
A
M
r
u
n
n
i
n
g
W
in
d
o
w
s
7
OS.
I
n
liter
atu
r
e,
m
aj
o
r
f
o
cu
s
i
s
o
n
lo
ca
tio
n
b
ased
p
r
iv
ac
y
[
2
4
-
2
6
]
.
B
u
t
in
o
u
r
ap
p
r
o
ac
h
,
o
u
r
m
ail
g
o
al
is
to
f
o
c
u
s
o
n
co
s
t,
s
ca
lab
ili
t
y
a
lo
n
g
with
lo
ca
tio
n
p
r
iv
ac
y
.
H
en
ce
i
n
t
h
i
s
s
ec
tio
n
,
w
e
h
a
v
e
d
is
cu
s
s
ed
t
h
e
r
es
u
lt
s
f
o
r
cr
ea
ti
n
g
r
an
d
o
m
s
u
b
r
eg
io
n
(
to
d
ec
r
ea
s
e
co
m
p
u
tatio
n
al
an
d
co
m
m
u
n
icatio
n
a
l
co
s
t)
in
s
p
atial
clo
ac
k
i
n
g
r
eg
io
n
u
s
i
n
g
d
en
s
it
y
b
a
s
ed
clu
s
ter
i
n
g
alg
o
r
ith
m
s
[
1
0
,
1
1
]
th
at
is
n
o
t a
v
a
ilab
le
in
liter
at
u
r
e.
W
e
ex
p
er
i
m
e
n
ted
t
h
e
p
er
f
o
r
m
an
ce
w
it
h
d
i
f
f
er
en
t
d
e
n
s
i
t
y
b
ased
clu
s
ter
i
n
g
al
g
o
r
ith
m
a
n
d
d
if
f
er
e
n
t
d
ataset
o
f
u
s
er
s
.
T
o
m
ea
s
u
r
e
p
er
f
o
r
m
an
ce
m
etr
ic
s
,
w
e
u
s
e
a
v
er
ag
e
co
m
p
u
tat
io
n
ti
m
e
tak
e
n
b
y
t
h
e
p
r
o
ce
s
s
es.
a)
Data
s
ets
W
e
h
av
e
u
s
ed
t
w
o
d
ataset
s
: 1
)
B
r
in
k
h
o
f
f
T
r
af
f
i
c
Data
s
et
[
3
0
,
31
]
an
d
2
)
Go
w
alla
d
atase
t [
32
].
1)
B
r
in
k
h
o
f
f
tr
af
f
ic
d
ataset
B
y
u
s
in
g
t
h
i
s
s
ta
n
d
ar
d
d
ataset
in
o
u
r
s
i
m
u
la
tio
n
w
h
e
n
a
u
s
er
i
s
s
e
n
d
in
g
t
h
eir
q
u
er
ie
s
to
L
B
S
p
r
o
v
id
er
s
.
W
e
u
s
e
B
r
in
k
h
o
f
f
[
3
0
]
n
et
w
o
r
k
-
b
a
s
ed
tr
af
f
ic
g
e
n
er
ato
r
s
i
m
u
l
ato
r
.
W
e
r
an
d
o
m
l
y
g
e
n
er
ate
v
a
r
io
u
s
d
ataset
o
f
5
0
,
1
0
0
,
2
0
0
,
5
0
0
,
1
0
0
0
,
2
0
0
0
m
o
b
ile
u
s
er
s
t
h
at
w
a
s
s
i
m
u
la
ted
o
n
th
e
r
ea
l
r
o
ad
m
ap
o
f
Ah
m
e
d
ab
ad
city
in
i
n
d
ia.
Fo
r
o
u
r
ex
p
er
i
m
en
ta
l
p
u
r
p
o
s
e,
w
e
g
en
er
ate
5
s
y
n
t
h
etic
d
atas
ets:
d
ataset1
,
d
ataset2
,
d
ataset3
,
d
ataset4
,
d
ataset5
u
s
i
n
g
B
r
in
k
h
o
f
f
’
s
tr
af
f
ic
d
ata
g
en
er
ato
r
to
o
l
[
31
]
.
Fig
u
r
e
4
s
h
o
w
s
th
e
f
o
o
tp
r
in
ts
o
f
1
,
0
0
0
m
o
b
ile
u
s
er
s
i
n
th
e
r
ea
l r
o
ad
m
ap
o
f
Old
e
n
b
er
g
,
Ger
m
a
n
y
,
g
en
er
ated
v
ia
B
r
in
k
h
o
f
f
T
r
af
f
ic
g
en
er
ato
r
.
Fig
u
r
e
4
.
T
h
e
f
o
o
tp
r
in
ts
o
f
1
,
0
0
0
m
o
b
ile
u
s
er
s
i
n
t
h
e
r
ea
l r
o
ad
m
ap
o
f
Old
e
n
b
er
g
,
Ger
m
a
n
y
,
g
en
er
ated
v
ia
B
r
in
k
h
o
f
f
T
r
af
f
i
c
g
en
er
ato
r
Evaluation Warning : The document was created with Spire.PDF for Python.
I
SS
N
:
2
0
8
8
-
8708
I
n
t J
E
lec
&
C
o
m
p
E
n
g
,
Vo
l.
9
,
No
.
6
,
Dec
em
b
er
2
0
1
9
:
5
3
7
6
-
5
3
8
5
5382
2)
Go
w
alla
d
atase
t
W
e
u
s
e
Go
w
alla
d
ata
s
et
[
32
]
b
ased
o
n
a
p
o
p
u
lar
lo
ca
tio
n
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t
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[
32
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SC
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t
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a.
RE
F
E
R
E
NC
E
S
[1
]
R
.
P
a
d
m
a
n
a
b
a
n
,
“
L
o
c
a
ti
o
n
P
riv
a
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y
in
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ti
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Ba
se
d
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ter
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ti
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n
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l
J
o
u
rn
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l
o
f
A
d
v
a
n
c
e
d
Rem
o
te S
e
n
sin
g
a
n
d
GIS
,
v
ol
.
2
,
p
p
.
3
9
8
-
4
0
4
,
2
0
1
3
.
[2
]
E
.
M
a
g
k
o
s,
“
Cr
y
p
to
g
ra
p
h
ic
Ap
p
r
o
a
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s
f
o
r
P
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y
P
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se
rv
a
ti
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n
in
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ti
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s
e
d
S
e
rv
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s:
A
S
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rv
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y
,
”
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ter
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J
o
u
rn
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o
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n
d
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ms
Ap
p
ro
a
c
h
(
ACM
)
,
v
ol
4
,
2
0
1
1
.
[3
]
G
.
Ya
n
g
,
e
t
a
l.
,
“
A
S
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rv
e
y
o
f
L
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ti
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n
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d
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e
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T
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n
o
lo
g
y
,
v
ol
.
8
,
2
0
1
3
.
[4
]
N
.
Ya
n
g
,
e
t
a
l
.
,
“
A
No
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e
l
P
e
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n
a
li
z
e
d
T
T
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,
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ter
n
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ti
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a
l
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rn
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o
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c
u
rity a
n
d
Its
Ap
p
li
c
a
t
io
n
s
,
v
o
l.
8
,
2
0
1
4
.
[5
]
A
.
S
o
lan
a
s,
e
t
a
l.
,
“
L
o
c
a
ti
o
n
P
r
i
v
a
c
y
in
L
o
c
a
ti
o
n
-
Ba
se
d
S
e
rv
ice
s:
Be
y
o
n
d
T
T
P
-
b
a
se
d
S
c
h
e
m
e
s,
”
Pro
c
e
e
d
in
g
s
of
th
e
1
st
I
n
ter
n
a
ti
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n
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l
W
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rk
sh
o
p
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n
Priva
c
y
in
L
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ti
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-
B
a
se
d
A
p
p
l
ica
ti
o
n
s,
2
0
0
8
.
[6
]
G
.
G
h
in
it
a
,
e
t
a
l.
,
“
P
riv
a
te
Qu
e
ries
in
L
o
c
a
ti
o
n
Ba
se
d
S
e
rv
ice
s:
A
n
o
n
y
m
iz
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rs
a
r
e
n
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t
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c
e
ss
a
r
y
,
”
ACM
S
IGM
OD
in
ter
n
a
t
io
n
a
l
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o
n
fer
e
n
c
e
o
n
M
a
n
a
g
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me
n
t
o
f
d
a
t
a
,
pp.
1
2
1
-
1
3
2
,
2
0
0
8
.
[7
]
G
.
G
h
in
i
ta,
e
t
a
l.
,
“
A
H
y
b
rid
Te
c
h
n
iq
u
e
f
o
r
P
riv
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te
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o
c
a
ti
o
n
-
Ba
se
d
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rie
s
w
it
h
Da
tab
a
se
P
ro
tec
ti
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n
,
”
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p
ri
n
g
e
r
Ad
v
a
n
c
e
s
in
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p
a
ti
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l
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n
d
T
e
m
p
o
ra
l
Da
ta
b
a
se
s
Vo
lu
me
5
6
4
4
o
f
th
e
se
rie
s
L
e
c
tu
re
No
tes
in
Co
mp
u
ter
S
c
ien
c
e
,
p
p
9
8
-
1
1
6
,
2
0
0
9
.
[8
]
C
.
Be
tt
in
i
,
e
t
a
l.
,
“
P
r
o
tec
ti
n
g
P
ri
v
a
c
y
Ag
a
in
st
L
o
c
a
ti
o
n
-
b
a
se
d
P
e
r
so
n
a
l
I
d
e
n
ti
f
ica
ti
o
n
,
”
W
o
rk
sh
o
p
o
n
S
e
c
u
re
Da
t
a
M
a
n
a
g
e
me
n
t
S
DM
2
0
0
5
:
S
e
c
u
re
Da
ta
M
a
n
a
g
e
me
n
t
,
p
p
.
1
8
5
-
1
9
9
,
2
0
0
6
.
[9
]
G
.
Ya
n
g
,
e
t
a
l.
,
“
A
S
u
rv
e
y
o
f
L
o
c
a
ti
o
n
-
Ba
se
d
P
riv
a
c
y
P
re
se
rv
in
g
,
”
J
o
u
rn
a
l
o
f
C
o
n
v
e
rg
e
n
c
e
I
n
fo
rm
a
ti
o
n
T
e
c
h
n
o
lo
g
y
,
v
ol
.
8
,
2
0
1
3
.
[1
0
]
J
.
L
iu
,
e
t
a
l.
,
“
P
r
iv
a
c
y
P
re
se
rv
in
g
Distrib
u
te
d
DBSCA
N Cl
u
ste
rin
g
,
”
A
CM
,
2
0
1
2
.
[1
1
]
P
.
B
.
Na
g
p
a
l
a
n
d
P
.
A
.
M
a
n
n
,
“
C
o
m
p
a
ra
ti
v
e
S
tu
d
y
o
f
De
n
sity
b
a
se
d
Cl
u
ste
rin
g
A
lg
o
rit
h
m
s,
”
In
ter
n
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ti
o
n
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l
J
o
u
rn
a
l
o
f
Co
m
p
u
ter
A
p
p
l
ica
ti
o
n
s
,
v
ol
.
2
7
,
2
0
1
1
.
[1
2
]
A
.
S
o
lan
a
s
a
n
d
A
.
M
.
Ba
ll
e
ste
,
“
A
TT
P
-
f
re
e
p
ro
to
c
o
l
f
o
r
lo
c
a
ti
o
n
p
riv
a
c
y
in
lo
c
a
ti
o
n
-
b
a
se
d
se
rv
ice
s,
”
El
se
v
ier
T
ra
n
sa
c
ti
o
n
s
o
n
Co
m
p
u
ter
Co
mm
u
n
ica
ti
o
n
s
,
v
ol
.
3
1
,
pp
.
1
1
8
1
-
1
1
9
1
,
2
0
0
8
.
[1
3
]
A
.
S
o
lan
as
a
n
d
A
.
M
.
Ba
ll
e
ste
,
“
P
r
iv
a
c
y
P
ro
tec
ti
o
n
in
L
o
c
a
ti
o
n
-
Ba
se
d
S
e
rv
ice
s
th
ro
u
g
h
a
P
u
b
li
c
-
Ke
y
P
riv
a
c
y
Ho
m
o
m
o
rp
h
ism
,
”
Pro
c
e
e
d
in
g
s
o
f
th
e
4
t
h
Eu
r
o
p
e
a
n
c
o
n
fer
e
n
c
e
o
n
Pu
b
li
c
Ke
y
In
fra
stru
c
t
u
re
:
th
e
o
ry
a
n
d
p
ra
c
ti
c
e
S
p
rin
g
e
r
,
2
0
0
7
.
[1
4
]
Y
.
Hu
a
n
g
a
n
d
R
.
V
is
h
w
a
n
a
th
a
n
,
“
P
riv
a
c
y
P
re
se
rv
in
g
G
ro
u
p
Ne
a
re
st
Ne
ig
h
b
o
r
Qu
e
ries
i
n
L
o
c
a
ti
o
n
-
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se
d
S
e
rv
ice
s
Us
in
g
Cry
p
to
g
ra
p
h
ic T
e
c
h
n
iq
u
e
s
,”
IEE
E
Glo
b
a
l
T
e
lec
o
mm
u
n
ica
ti
o
n
s Co
n
fer
e
n
c
e
GLOBE
COM
,
2
0
1
0
.
Evaluation Warning : The document was created with Spire.PDF for Python.
I
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N
:
2
0
8
8
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8708
I
n
t J
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&
C
o
m
p
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n
g
,
Vo
l.
9
,
No
.
6
,
Dec
em
b
er
2
0
1
9
:
5
3
7
6
-
5
3
8
5
5384
[1
5
]
V
.
Ja
riw
a
la
a
n
d
D
.
Jin
w
a
la,
“
Ev
a
lu
a
ti
n
g
Ho
m
o
m
o
rp
h
ice
En
c
ry
p
ti
o
n
A
lg
o
rit
h
m
s
f
o
r
P
riv
a
c
y
in
W
irele
ss
S
e
n
so
r
Ne
tw
o
rk
,
”
In
ter
n
a
ti
o
n
a
l
J
o
u
rn
a
l
o
f
A
d
v
a
n
c
e
me
n
ts i
n
c
o
mp
u
ti
n
g
T
e
c
h
n
o
l
o
g
y
,
v
ol
.
3,
2
0
1
1
.
[1
6
]
X
.
Z
h
u
,
e
t
a
l.
,
“
A
L
o
c
a
ti
o
n
P
r
iv
a
c
y
-
P
re
se
rv
in
g
P
ro
t
o
c
o
l
Ba
se
d
o
n
Ho
m
o
m
o
rp
h
ic
En
c
ry
p
ti
o
n
a
n
d
Ke
y
Ag
re
e
m
e
n
t,
”
In
ter
n
a
t
io
n
a
l
C
o
n
fer
e
n
c
e
o
n
I
n
fo
r
ma
ti
o
n
S
c
ien
c
e
a
n
d
Cl
o
u
d
Co
m
p
u
ti
n
g
C
o
mp
a
n
i
o
n
IE
EE
,
2
0
1
4
.
[1
7
]
M
.
A
.
T
a
lo
u
k
i
a
n
d
A
.
B
.
Da
stje
rd
i,
“
Ho
m
o
m
o
rp
h
ic
En
c
ry
p
ti
o
n
to
P
re
se
rv
e
L
o
c
a
ti
o
n
P
riv
a
c
y
,
”
In
ter
n
a
ti
o
n
a
l
J
o
u
r
n
a
l
o
f
S
e
c
u
rity
a
n
d
Its
Ap
p
li
c
a
ti
o
n
s
,
v
o
l.
6
,
2
0
1
2
.
[1
8
]
M
.
W
e
rn
k
e
,
e
t
a
l.
,
“
A
Cla
ss
i
f
ic
a
ti
o
n
o
f
L
o
c
a
ti
o
n
P
riv
a
c
y
A
tt
a
c
k
s
a
n
d
A
p
p
ro
a
c
h
e
s
,
”
Per
so
n
a
l
a
n
d
Ub
i
q
u
it
o
u
s
Co
mp
u
t
in
g
,
S
p
ri
n
g
e
r
-
Ver
la
g
,
v
ol
.
1
8
,
p
p
1
6
3
-
1
7
5
,
2
0
1
4
.
[1
9
]
R
.
G
u
p
ta
a
n
d
U
.
P
.
Ra
o
,
“
A
n
Ex
p
lo
ra
ti
o
n
t
o
L
o
c
a
ti
o
n
Ba
se
d
S
e
rv
ice
a
n
d
Its
P
riv
a
c
y
P
re
se
rv
i
n
g
T
e
c
h
n
iq
u
e
s:
A
S
u
rv
e
y
,
”
J
o
u
rn
a
l
W
ire
les
s
Per
so
n
a
l
Co
mm
u
n
ica
ti
o
n
s:
A
n
In
ter
n
a
ti
o
n
a
l
J
o
u
rn
a
l
a
rc
h
ive
,
v
ol
.
96
,
p
p
.
1
9
7
3
-
2
0
0
7
,
2
0
1
7
.
[2
0
]
A
.
K
.
Ty
a
g
i
a
n
d
N.
S
re
e
n
a
th
,
“
P
re
se
rv
in
g
L
o
c
a
ti
o
n
P
riv
a
c
y
in
L
o
c
a
ti
o
n
Ba
se
d
S
e
rv
ice
s
a
g
a
in
st
S
y
b
il
A
tt
a
c
k
s,
”
In
ter
n
a
t
io
n
a
l
J
o
u
rn
a
l
o
f
S
e
c
u
rity
a
n
d
Its
A
p
p
li
c
a
ti
o
n
s
,
v
o
l
.
9
,
2
0
1
5
.
[2
1
]
T
.
P
e
n
g
,
e
t
a
l.
,
“
En
h
a
n
c
e
d
L
o
c
a
ti
o
n
P
riv
a
c
y
P
re
se
rv
in
g
S
c
h
e
m
e
in
L
o
c
a
ti
o
n
-
Ba
se
d
S
e
rv
ice
s
,”
IEE
E
S
Y
S
T
EM
S
J
OU
RNA
L
,
2
0
1
4
.
[2
2
]
A
.
K
.
Ty
a
g
i
a
n
d
N.
S
re
e
n
a
th
,
“
F
u
tu
re
C
h
a
ll
e
n
g
in
g
Is
su
e
s
in
L
o
c
a
ti
o
n
b
a
se
d
S
e
rv
ice
s
,
”
In
ter
n
a
ti
o
n
a
l
J
o
u
r
n
a
l
o
f
Co
mp
u
ter
A
p
p
li
c
a
ti
o
n
s
,
v
ol
.
1
1
4
,
2
0
1
5
.
[2
3
]
R
.
J.
P
a
ti
l
,
e
t
a
l.
,
“
A
n
a
l
y
sis
o
n
P
re
se
rv
in
g
L
o
c
a
ti
o
n
P
riv
a
c
y
,
”
In
ter
n
a
t
io
n
a
l
J
o
u
rn
a
l
o
f
Ad
v
a
n
c
e
d
Res
e
a
rc
h
i
n
Co
mp
u
ter
S
c
ien
c
e
a
n
d
S
o
f
twa
re
En
g
i
n
e
e
rin
g
,
v
ol
.
5,
2
0
1
5
.
[2
4
]
B
.
Am
ro
,
e
t
a
l.
,
“
En
h
a
n
c
i
n
g
p
riv
a
c
y
in
c
o
ll
a
b
o
ra
ti
v
e
traf
f
ic
-
m
o
n
it
o
rin
g
sy
ste
m
s u
sin
g
a
u
to
n
o
m
o
u
s l
o
c
a
ti
o
n
u
p
d
a
te,
”
IET
In
tell
ig
e
n
t
T
ra
n
sp
o
rt S
y
ste
ms
,
v
o
l
.
7
,
p
p
.
3
8
8
-
3
9
5
,
2
0
1
3
.
[2
5
]
S
.
P
a
ti
l
,
e
t
a
l.
,
“
Hid
in
g
Us
e
r
P
riv
a
c
y
in
L
o
c
a
ti
o
n
Ba
se
S
e
rv
ic
e
s
T
h
ro
u
g
h
M
o
b
il
e
Co
ll
a
b
o
ra
ti
o
n
:
A
Re
v
i
e
w
,”
In
ter
n
a
t
io
n
a
l
C
o
n
fer
e
n
c
e
o
n
C
o
mp
u
t
a
ti
o
n
a
l
In
telli
g
e
n
c
e
a
n
d
Co
m
mu
n
ica
t
io
n
Ne
two
rk
s IE
EE
,
2
0
1
5
.
[2
6
]
R
.
S
h
o
k
ri,
e
t
a
l.
,
“
Hid
i
n
g
in
th
e
M
o
b
i
le
Cro
w
d
:
L
o
c
a
ti
o
n
P
r
iv
a
c
y
th
ro
u
g
h
C
o
ll
a
b
o
ra
ti
o
n
,”
IEE
E
T
ra
n
sa
c
ti
o
n
s
O
n
De
p
e
n
d
a
b
le A
n
d
S
e
c
u
re
Co
mp
u
ti
n
g
,
S
p
e
c
i
a
l
Iss
u
e
On
“
S
e
c
u
rity
A
n
d
Priv
a
c
y
In
M
o
b
il
e
Pl
a
tf
o
rm
s
,
2
0
1
4
.
[2
7
]
Ra
th
o
d
A
.
a
n
d
Ja
riw
a
la
V
.
,
“
H
y
b
rid
Cry
p
to
g
ra
p
h
ic
Ba
se
d
A
p
p
ro
a
c
h
f
o
r
P
riv
a
c
y
P
re
se
rv
a
ti
o
n
in
L
o
c
a
ti
o
n
-
Ba
se
d
S
e
rv
ice
s,
”
in
W
o
u
n
g
a
n
g
I.
a
n
d
Dh
u
ra
n
d
h
e
r
S
.
(e
d
s)
,
2
n
d
I
n
ter
n
a
ti
o
n
a
l
Co
n
fer
e
n
c
e
o
n
W
ire
les
s
In
telli
g
e
n
t
a
n
d
Distrib
u
ted
En
v
iro
n
me
n
t
f
o
r
Co
mm
u
n
ic
a
ti
o
n
.
W
IDECOM
2
0
1
8
.
L
e
c
tu
re
No
tes
o
n
Da
t
a
E
n
g
in
e
e
rin
g
a
n
d
Co
mm
u
n
ica
ti
o
n
s T
e
c
h
n
o
l
o
g
i
es
,
S
p
rin
g
e
r,
Ch
a
m
,
v
o
l
.
27
,
2
0
1
9
.
[2
8
]
S
.
R.
S
h
a
stry
,
e
t
a
l.
,
“
G
e
n
e
ra
ti
n
g
:
ra
n
d
o
m
re
g
io
n
s
i
n
S
p
a
ti
a
l
c
lo
a
k
in
g
a
lg
o
rit
h
m
f
o
r
l
o
c
a
ti
o
n
p
r
iv
a
c
y
p
re
se
rv
a
ti
o
n
,
”
IOS
R
J
o
u
r
n
a
l
o
f
Co
mp
u
ter
E
n
g
i
n
e
e
rin
g
,
IOS
R
-
J
CE
.,
v
ol
.
9
,
p
p
.
46
-
49
,
2
0
1
3
.
[2
9
]
Ra
th
o
d
A
.
a
n
d
Ja
riw
a
la
V
.
,
“
In
v
e
stig
a
ti
o
n
o
f
P
riv
a
c
y
Is
su
e
s
in
Lo
c
a
ti
o
n
-
Ba
se
d
S
e
rv
ice
s,
”
i
n
S
a
P
.
,
e
t
a
l.
,
(e
d
s)
,
“
Re
c
e
n
t
F
in
d
in
g
s
i
n
I
n
telli
g
e
n
t
C
o
m
p
u
ti
n
g
T
e
c
h
n
iq
u
e
s
,”
A
d
v
a
n
c
e
s
in
In
tel
li
g
e
n
t
S
y
ste
ms
a
n
d
C
o
mp
u
ti
n
g
,
S
p
r
in
g
e
r,
S
in
g
a
p
o
re
,
vol
.
7
0
7
,
2
0
1
9
.
[3
0
]
M
.
W
e
rn
k
e
,
e
t
a
l.
,
“
A
Clas
si
f
ic
a
t
io
n
o
f
L
o
c
a
ti
o
n
P
riv
a
c
y
A
tt
a
c
k
s
a
n
d
A
p
p
ro
a
c
h
e
s,
”
S
p
ri
n
g
e
r,
v
ol
.
1
8
,
p
p
.
1
6
3
-
1
7
5
,
2
0
1
4
.
[3
1
]
Y
.
W
a
n
g
,
e
t
a
l.
,
“
L
o
c
a
ti
o
n
-
a
w
a
re
L
o
c
a
ti
o
n
P
riv
a
c
y
P
r
o
tec
t
io
n
f
o
r
L
o
c
a
ti
o
n
-
b
a
se
d
S
e
rv
ice
s
,
”
P
ro
c
e
e
d
in
g
s
-
I
EE
E
INFOCOM
,
pp
.
1
9
9
6
-
2
0
0
4
,
2
0
1
2
.
[3
2
]
Y
.
L
iu
,
e
t
a
l.
,
“
Ex
p
lo
it
in
g
G
e
o
g
ra
p
h
ica
l
Ne
ig
h
b
o
r
h
o
o
d
C
h
a
ra
c
teristics
f
o
r
L
o
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