Trust is the willingness to be vulnerable to the actions of another party based on the expectation that the other will perform a particular action important to the person doing the trusting. This is regardless of whether the person can monitor or control the party they are trusting. Trust is a contextual quality and mechanism of human relations, of being social. There is no need to trust that 2+2 will equal 4 tomorrow, it just will. Ditto other deterministic processes such as cryptography.