Ensuring physical locality of entities sharing data

A method and system for ensuring that data is only distributed within a certain physical area are disclosed. In one embodiment, a method provides that data is distributed only if the distance between a source and a sink is within a distance threshold. Under this system, the distance between the source and the sink may be estimated directly or indirectly. In some embodiments, the distance may be estimated by estimating the propagation delay for a signal traversing between the devices. The physical distance between the devices may be determined from the propagation delay. If the physical distance is outside a threshold value, the source may be prohibited from transmitting the data or the sink may refuse to display the data.