Trust in Computer Systems and the Cloud. Mike Bursell

Trust in Computer Systems and the Cloud - Mike Bursell


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that the payoffs are immediate, clear, and motivating.

       Teach players to care about each other.

       Teach reciprocity (rewarding positive actions—typically cooperation—and punishing negative actions—typically betrayal).

       Improve recognition abilities (being able to recognise what the other party's strategy is).

      This does not mean, however, that game theory has nothing to offer us. What Axelrod's tactics to encourage cooperation seem to be promoting are ways to build some sort of trust between the two parties. Let us revisit our definition of trust and apply it to game theory:

       “Trust is the assurance that one entity holds that another will perform particular actions according to a specific expectation”.

      We need, of course, to consider our corollaries as well: how do they apply in this case?

       First Corollary “Trust is always contextual”.

       Second Corollary “One of the contexts for trust is always time”.

       Third Corollary “Trust relationships are not symmetrical”.

      Reputation and Generalised Trust

      The Prisoner's Dilemma is not the only type of game covered in the field of game theory. There are many, of which most are two-player games, and most can also have multiple participants (with no theoretical limit). The two-player games serve to give an example of how assurances about future behaviour—what we are referring to as trust relationships—can be formed between two participants.

      What about the case for multiple participants? When I set about forming a trust relationship “from scratch”—with no prior interactions—to someone (let us call her Alice), then I do so based on my expectations, biases, and interactions over time. If, on the other hand, somebody (we will call her Carol) asks me for information on Alice in order for her to form an initial opinion, and then asks multiple other people who have also formed a trust relationship to Alice for the same or similar information, then something else is happening: Carol is finding out information not first-hand, but based on information from others.

      The standard term for this is reputation, and it does not map directly from a trust relationship that Carol has to Alice but is a second-order construct. Carol cannot directly map my views on my trust relationship to Alice, alongside the views of others on their trust relationships to Alice, directly to her trust relationship to Alice: rather, she derives enough information to describe a reputation that she can relate to Alice and use to decide how best to form a trust relationship.

      The reputation approach is interesting because rather than having to start her trust relationship to Alice from scratch or with only the tools that she has (her experience, biases, and some expectations), Carol starts with some specific information about Alice that she can use. We can think of this type of information as inputs to the idea of “trustworthiness” proposed by some of the writers we have mentioned when considering human-to-human trust.

      We know in our day-to-day human interactions that reputations can be ill-formed or unfairly earned and also that they can change significantly over time. We will look at indirect trust relationships in Chapter 3, “Trust Operations and Alternatives”, and at the importance of time in Chapter 7, “The Importance of Time”, but another point arises from reputations: over the many years that humans have grown into larger and larger groups, creating societies and forming organisations, reputations are important for another type of trust relationship. This is the area on which Schneier spends much attention, as evidenced by his chapter headings on organisations, corporations, and institutions, and which we can broadly label institutional trust.


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