On protecting the integrity of sensor data

Wireless sensors typically operate in uncontrolled and possibly hostile environment. Thus, sensors have a high risk of being captured and compromised by an adversary. Traditional security schemes are computationally expensive, because they introduce overhead which shortens the life of the sensors. Watermarking schemes are usually light weight and do not require extensive computing and power resources in comparison with traditional security techniques. Thus they can be attractive alternative for wireless sensor applications. This paper proposes a fragile watermarking scheme S-SGW to provide integrity for sensor data. The proposed scheme is a simplification of a technique proposed by Guo et.al. for data streams. S-SGW requires less computing power than the original technique and thus; more suitable for WSNs. Yet it provides the same sensitivity to malicious updates. Data elements generated by sensors are organized into groups with variable sizes. A secret watermark is generated from every two consecutive groups. The watermark is then embedded in the earlier group by replacing the least significant bits in the data element. The security analysis S-SGW is similar to that of Guo et.al. technique, thus, the experimental section compares the performance and overhead of the two techniques. The experimental results show that watermark composition as well as the embedding and the extraction algorithms of the S-SGW are much faster than that of Guo et.al.