A method for providing an answer to an input query respective of a user using a user device comprises collecting data respective of the user by using a plurality of sensors on the user device, wherein the plurality of sensors sense the user activity on the user device; generating a plurality of uniquifiers from the data, wherein each uniquifier of the plurality of uniquifier characterizes the user; evaluating periodically the plurality of uniquifiers; storing at least the evaluated plurality of uniquifiers in a memory of the user device; and responsive to the input query, providing an answer based on at least one evaluated uniquifier of the evaluated plurality of uniquifiers stored in the memory