Location corroborations by mobile devices without traces

A location corroboration of a person is a proof, in the form of a digital record, indicating that this person was at a particular place at a given time. That is, given a user u, a location l and a time t, a location corroboration is a certified evidence that u was at location l at time t. Such corroborations can be used in legal procedures, help solving personal disputes or enable services that rely on knowing with certainty the location of a user at a given time. A corroboration without traces means that the user location is not stored in any public server or in any other public entity, to protect the user privacy. In this paper we present the problem of producing a location corroboration without traces, using a mobile device, and we discuss possible solutions to it.