Abstract-Secure cooperation incentive schemes usually use public key cryptography, which incur too heavy overhead to be used efficiently in limited-resource nodes. In this paper, we propose a novel incentive scheme that requires public-key operations only for the first packet in a series. The efficient hashing operations are used in the successive packets so that the overhead of the packet series converges to that of the hashing operations. Our evaluations demonstrate that the proposed scheme is secure and has much less overhead than the public key cryptography based incentive schemes.