  When deploying wireless sensor networks (WSNs) in public environments it may
become necessary to secure their data storage and transmission against possible
attacks such as node-compromise and eavesdropping. The nodes feature only small
computational and energy resources, thus requiring efficient algorithms. As a
solution for this problem the TinyPEDS approach was proposed in [7], which
utilizes the Elliptic Curve ElGamal (EC-ElGamal) cryptosystem for additive
homomorphic encryption allowing concealed data aggregation. This work presents
an optimized implementation of EC-ElGamal on a MicaZ mote, which is a typical
sensor node platform with 8-bit processor for WSNs. Compared to the best
previous result, our implementation is at least 44% faster for fixed-point
multiplication. Because most parts of the algorithm are similar to standard
Elliptic Curve algorithms, the results may be reused in other realizations on
constrained devices as well.
