End to end secure data aggregation scheme for wireless sensor networks that are based on public key cryptography generally use elliptic curves. However elliptic curve based protocols require messages to be mapped to elliptic curves before performing any operations and finally reverse mapped to retrieve the message back. No mapping function, however, which is both homomorphic and has an efficient reverse mapping function is currently known. The mapping functions used in many previous protocols require brute forcing to reverse map the message from a point on the elliptic curve. This solution may be feasible on a base station with unlimited energy and processing power but it means that decrypting becomes very inefficient on ordinary sensors. We propose a secure data aggregation algorithm based on bilinear pairing that avoids this problem and makes decrypting data feasible on ordinary sensors.