Watermarking sensor data for protecting the integrity

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 two fragile watermarking schemes S-SGW and FWC to provide integrity for sensor data. The proposed scheme S-SGW is a simplification of a technique proposed by Guo et.al. for data streams. S-SGW and FWC 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. In S-SGW 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 performance evaluations show that watermark composition as well as the embedding and the extraction algorithms of the S-SGW and FWC are much faster than that of Guo et.al.