A trusted party is presumed to seek to fulfill
policies,
ethical codes,
law and their previous promises.
Trust does not need to involve belief in the good character, vices, or morals of the other party. Persons engaged in a criminal activity usually trust each other to some extent. Also, trust does not need to include an action that you and the other party are mutually engaged in. Trust is a statement about what is otherwise unknown -- for example, because it is far away, cannot be verified, or is in the future.
In the social sciences, the subtleties of trust are a subject of ongoing research. In sociology and psychology the degree to which one party trusts another is a measure of belief in the honesty, benevolence and competence of the other party. Based on the most recent research, a failure in trust may be forgiven more easily if it is interpreted as a failure of competence rather than a lack of benevolence or honesty. In economics trust is often conceptualized as reliability in transactions. In all cases trust is a heuristic decision rule, allowing the human to deal with complexities that would require unrealistic effort in rational reasoning.
From this perspective, trust is a mental state, which cannot be measured directly. Confidence in the results of trusting may be measured through behavior, or alternatively, one can measure self-reported trust (with all the caveat surrounding that method). Trust may be considered a moral choice, as in the legend of Damon and Pythias, or at least a heuristic, allowing the human to deal with complexities that outgo rationalistic reasoning. In this case, machine-human trust is meaningless, because computers have no moral sense and rely on rational computations. Any trust in a device under this characterization is computer-mediated trust of the user of the machine in the designer and creator of the device; who has implemented the rational rules into the device. Francis Fukuyama and Tyler are academics who advocate this conception of trust – as moral and not directly observable.