A system, method and program product for authenticating a device. An authentication service is provided having: a data management system for periodically collecting and storing signature data from each of a set of registered devices, wherein the signature data includes a plurality of data points, and wherein at least one of the data points includes a device usage characteristic; a system for obtaining a temporal signature state (TSS) vector of a device in response to a transaction request from the device, wherein the TSS vector includes values for a selected subset of the data points forming the signature data; and an authenticator for comparing the TSS vector of the device with stored signature data in order to authenticate the device.