Wireless sensor networks that use a mobile sink to collect sensor data along a predetermined path raise a new security challenge: without verifying the source of the data request message, the network will become vulnerable to attacks. We propose an efficient security scheme, which divides the sink’s data collection path into grids, sensors in each grid, uses secret keying in-formation and collision-resistant hash functions to authenticate the source of beacons. Through probabil-istic analysis and definitive simulation, the proposed scheme shows with 60% of the grids under wormhole attacks, the probability that a node reply to a malicious beacon is 0.1.