  Due to resource restricted sensor nodes, it is important to minimize the
amount of data transmission among sensor networks. To reduce the amount of
sending data, an aggregation approach can be applied along the path from
sensors to the sink. However, as sensor networks are often deployed in
untrusted and even hostile environments, sensor nodes are prone to node
compromise attacks. Hence, an end-to-end secure aggregation approach is
required to ensure a healthy data reception. In this paper, we propose two
layers for secure data aggregation in sensor networks. Firstly, we provide an
end-to-end encryption scheme that supports operations over cypher-text. It is
based on elliptic curve cryptography that exploits a smaller key size, allows
the use of higher number of operations on cypher-texts, and prevents the
distinction between two identical texts from their cryptograms. Secondly, we
propose a new watermarking-based authentication that enables sensor nodes to
ensure the identity of other nodes they are communicating with. Our experiments
show that our hybrid approach of secure data aggregation enhances the security,
significantly reduces computation and communication overhead, and can be
practically implemented in on-the-shelf sensor platforms.
