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Routing Table
Keys
001
1
Peer 6
01
Peer 3
1. Query for Key 110
Routing Table
Keys
010
011
Routing Table
Keys
100
101
Peer 1
1
Peer 6
0
Peer 3
2. Route Query
00
Peer 1
11
Peer 4
Peer 6
Peer 2
Peer 1
Trust Manager
3. Route Query
Feedback
Submission
Trust
Evaluation
Routing Table
Keys
001
Routing Table
Keys
010
011
Peer 6
Peer 5
Peer 3
P2P
Network
Peer 2
1
Peer 4
1
Peer 4
Peer 4
01
Peer 2
00
Peer 5
Data
Locator
Trust
Data
Peer 5
Peer 3
4. Return Data
Peer 4
Routing Table
Keys
110
0
Peer 1
10
Peer 6
(a) architecture
(b) data location
FIGURE
6.4:
System
architecture
and
data
location
mechanism
in
PeerTrust [Xiong and Liu, 2004].
locator, which routes the data to appropriate peers for storage. Secondly, it is
responsible for evaluating the trustworthiness of a particular peer. This task is
performed in two steps. It first collects trust data about the target peer from
the network through the data locator and then computes the trust value.
Trust data location is based on P-Grid [Aberer, 2001]. As shown in Fig-
ure 6.4(b), the trust data about a peer u, i.e., feedback u receives for each
transaction, are stored at designated peers that are located by hashing a
unique ID of peer u to a data key. Each piece of feedback includes the fol-
lowing information: ID of peer u as the data key, timestamp, or counter of
the transaction, feedback for that transaction, ID of the peer who provides
feedback, and other applicable transaction contexts. Each peer is responsible
for multiple keys and maintains a routing table for other keys. When a peer
receives a search or update request with a data key that it is not responsible
for, it forwards the request according to its routing table. Consequently, the
storage cost at each peer is proportional to the degree of replication and the
amount of history information data that it needs to store.
Simulation results indicated that PeerTrust is effective in combating col-
lusion attacks and has a reasonably low error in trust computations.
6.4 Trust-χ
Motivated by the observation that many previous work in trust modeling
mainly focused on only one aspect of trust negotiation such as policy and
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