Information Technology Reference
In-Depth Information
Chapter 6
Trust
6.1 Introduction
By nature of a P2P system, trust is a fundamental issue because each peer
interacts with another peer which does not have any well-known authority
(as in a Web server) and worse still, may “disappear” afterward. Indeed, even
for a fully cooperative peer (possibly due to the existence of an incentive
system), it is necessary for the peer to determine whether its counterpart in
a P2P transaction (e.g., a file downloading operation) is trustworthy or not.
For instance, in simple terms, an untrustworthy peer might be one which
deliberately injects wrong file data into the network. Consequently, a “good”
peer might download some malware from an untrustworthy peer.
There are at least three important issues [Li and Singhal, 2007, Mondal
and Kitsuregawa, 2006, Suryanarayana et al., 2005] in the design of a trust
management system for P2P networks.
1. We need to quantify “trust” so that each peer can compute the trust
values of other peers.
2. We need to specify where the trust values should be stored and main-
tained. Should we require every peer to store the trust values of every
other peer? What about consistency of trust values?
3. We need to come up with a communication protocol for exchanging trust
values among peers. More importantly, a proper aggregation mechanism
must be designed so that each peer can improve the accuracy of its local
trust values of other peers by incorporating the trust values sent from
remote peers.
In this section, we survey several recently proposed trust management
schemes that provide practical answers to the above questions.
6.1.1 Trust Modeling
Azzedin and Maheswaran [Azzedin and Maheswaran, 2003, Azzedin and
Maheswaran, 2004] suggested a practical trust computation and management
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