Systems and methods may provide for obtaining a seed value from a location on a beacon device, using the seed value to initiate generation of a pseudo random number (PRN) tree having time-dependent branches, and sending a beacon signal based on the PRN tree and a timing schedule that corresponds to the time-dependent branches. Additionally, a PRN may be received, via an out-of-band link, at an observation device, wherein the PRN is associated with a particular time period. In one example, the PRN may be used by the observation device to generate a subset of a PRN number tree that corresponds to the particular time period. The observation device may also conduct a proximity determination of whether a detected beacon signal corresponds to one or more time-dependent branches of the subset of the PRN tree.