1. A processor-implemented method of measuring trust of a first device from a second device, comprising: receiving a communication from the first device that requests execution of a function within the second device; calculating on the second device a trust score for the first device, the trust score calculated at least in part based on a physical distance between the first device and the second device and a measurement of a duration of an encounter between the first device and the second device, wherein the trust score is calculated prior to communicating a response to the first device; retrieving a threshold trust score from a memory of the second device, the threshold trust score having a minimum trust score associated with the function; comparing the calculated trust score to the threshold trust score; if the calculated trust score equals or exceeds the threshold trust score, then executing the function; and if the calculated trust score is less than the threshold trust score, then denying execution of the function.