The Trust Game: from Anonymity to Reputation
Professor Ioanis Nikolaidis,
University of Alberta
Trust is usually seen as a pre-existing property between transacting
entities. The question of how trust came to be established in the first
place is usually left unspecified. There exist purely mechanistic ways
to extending trust but are based on pre-existing trust to somebody else
(e.g., CAs in PKI). Yet, in everyday life trust relationships are formed
in a much more flexible manner and trust is established and dissolved
all the time. Interestingly, identity and trust are not so strongly
inter-related as one might think at first. For example, we trust people
who are anonymous (or rather pseudonymous) as long as they behave in
the manner that we expect them to, or have been "nice" to us in the
past. In some cases trust is established when we risk transaction(s)
at the benefit of collecting information (via feedback) to form a good
or bad impression about a transacting peer. Mapping the maintenance
of trust relationships to automated processes (protocols) adhered to
by mobile wireless devices (the closest we have to ad hoc "social"
devices) is a challenging task. Networks of such devices are also
severely limited in terms of scalability, further limiting our options
in designing appropriate protocols (we want to be frugal in terms of
bandwidth). Therefore, available solutions favor peer-to-peer one-hop
transactions. Starting with one such protocol, a practical anonymous P2P
file sharing protocol, we will motivate the discussion about schemes
for trust establishment and maintenance, we will then review some of
the proposed reputation-based schemes (like CORE), provide a critique
on their strengths as well as their blind spots, and also consider how
societies of such devices, that rely on cooperation, survive (or not)
when subjected to "noisy" observations of their peers' actions.