Wireless Sensor Networks (WSNs) provide an extensible and effective means to monitor large and geographically diverse areas. Nodes in a WSN are characterized by very strict constraints in terms of computing power and energy consumption, as a result of which efficient and secure data aggregation techniques are being proposed as enabling technology for reducing network load, while at the same time providing high sensing accuracy and data integrity. In this paper, we present an hybrid mesh/sensor network architecture based on a sharing of tasks between mesh routers and sensor nodes. Our architecture is particularly suitable to realize an application agnostic mesh backhaul, able to concurrently support multiple WSNs while ensuring both end-to-end encryption and hop-by- hop authentication. Simulation analyses have shown that the proposed scheme can significantly reduce the network load while preserving data confidentiality and integrity. Finally, a real-world prototype has been implemented and tested over a small scale testbed confirming the simulation results.