Information Technology Reference
In-Depth Information
Fig. 1.
Steps of Produre
as a false one, the credibility will decrease faster than it increase. Considering the client
c
and a proximity
p
in the results, the credibility of
c
with respect to
p
,
R
c
(
p
)
,isas
follows (the initial value to an unknown proximity is always 0):
min(1
,R
c
(
p
)
+
α
i
)
if
c
regards
p
as a true proximity,
R
c
(
p
)
=
(3)
α
d
n
2
)
max(
−
1
,R
c
(
p
)
−
otherwise.
where
-
α
i
(
α
d
): the reward (penalty) given to
p
for each good (bad) proximity feedback.
The relation
α
d
>α
i
assures that
R
c
(
u
)
decreases faster than it increases. The
selections of
α
i
and
α
d
are based on the specific requirement of application.
-
n
: the number of consecutive wrong proximity results which means
R
c
(
p
)
decreases
exponentially when
n
increases.
In Equation 3, the credibility of
c
with respect to
p
decreases faster than it increases.
The advantage is obvious: malicious users who always try to pretend to be proximities
of others will be severely penalized because of the weight which is
α
d
by the square of
the number of consecutive wrong proximity results.
2.4
Key Management
The key management center
K
mentioned in Equation 2 is in charge of generating pub-
lic and private key pairs for the processing center and each user in the location tagging
system, maintaining and destroying the public and private key pairs when necessary.
In Produre, all the users and the processing center have their own public and pri-
vate key pair. During the transmission of location tags, the content is encrypted by the
receiver's public key and the sender's private key for confidentiality and authentica-
tion. The sending content when considering encryption from the client's perspective is
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