Wireless sensor network (WSN) using network coding is vulnerable to pollution attacks. Existing authentication schemes addressing this attack either burden the sensor node with a higher computation overhead, or fail to provide an efficient way to mitigate two recently reported attacks: tag pollution attacks and repetitive attacks, which makes them inapplicable to WSN. This paper proposes an efficient hybrid cryptographic scheme for WSN with securing network coding. Our scheme can resist not only normal pollution attacks, but the emerging tag pollution and repetitive attacks in an efficient way. In particular, our scheme is immediately suited for distributing multiple generations using a single public key. Experimental results show that our scheme can significantly improve the computation efficiency at a sensor node under the two above-mentioned attacks.