Sensors_**2010**, _10_, 2770-2792; doi:10.3390/s100402770  
_Series of_  
ISSN **1424-8220**  
www.mdpi.com/journal/sensors  
_Article_  
**Acquiring Authentic Data in Unattended Wireless Sensor Networks**  
**[PERSON] \({}^{1,2}\), [PERSON] \({}^{3}\), [PERSON] \({}^{1,\star}\), [PERSON] \({}^{2}\) and [PERSON] \({}^{3,4}\)**  
\({}^{1}\) Institute of Information Science, Academia Sinica, Taipei, Taiwan;  
E-Mail: [EMAIL_ADDRESS] (C.-M.Y. ); [EMAIL_ADDRESS] (C.-S.L.) \({}^{2}\) Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan;  
E-Mail: [EMAIL_ADDRESS]  
\({}^{3}\) Department of Electrical Engineering, National Dong Hwa University, Hualian, Taiwan;  
E-Mail: [EMAIL_ADDRESS] (C.-Y.C.) \({}^{4}\) Department of Electronic Engineering and Institute of Computer Science & Information Engineering, National Ilan University, I-Lan, Taiwan; E-Mail: [EMAIL_ADDRESS] (H.-C.C.) \({}^{\star}\) Author to whom correspondence should be addressed; E-Mail: [EMAIL_ADDRESS];  
Tel. : +886-2-2788-3799#1513; Fax: +886-2-2782-4814. _Received: 10 February 2010; in revised form: 25 February 2010 / Accepted: 16 March 2010 / Published: 26 March 2010_  
An Unattended Wireless Sensor Network (UWSN) can be used in many applications to collect valuable data. Nevertheless, due to the unattended nature, the sensors could be compromised and the sensor readings would be maliciously altered so that the sink accepts the falsified sensor readings. Unfortunately, few attentions have been given to this authentication problem. Moreover, existing methods suffer from different kinds of DoS attacks such as Path-Based DoS (PDoS) and False Endorsement-based DoS (FEDoS) attacks. In this paper, a scheme, called AAD, is proposed to Acquire Authentic Data in UWSNs. We exploit the collaboration among sensors to address the authentication problem. With the proper design of the collaboration mechanism, AAD has superior resilience against sensor compromises, PDoS attack, and FEDoS attack. In addition, compared with prior works, AAD also has relatively low energy consumption. In particular, according to our simulation, in a network with \(1,000\) sensors, the energy consumed by AAD is lower than \(30\%\) of that consumed by the existing method, ExCo. The analysis and simulation are also conducted to demonstrate the superiority of the proposed AAD scheme over the existing methods. **Keywords:** unattended wireless sensor network; UWSN; authentication Introduction  
The use of wireless sensor networks (WSNs) on data gathering applications has been popularized in recent years. Since WSNs could be deployed in the hostile environments, one of the fundamental issues is how to secure the collected data. Unfortunately, with the consideration of the sensors' scarce resources, the security issue becomes very challenging because conventional computationally-intensive cryptographic primitives cannot be utilized. WSNs considered in the literature are usually assumed to have a constant connection between sensors and a trusted data collection unit, e.g., the sink. From the security point of view, in such a scenario, sensors can collect and then report the sensitive data to the sink at will. With the cryptographic primitives such as encryption and authentication, the confidentiality and authenticity of the transmitted sensed data can be guaranteed. More importantly, this avoid storing a large amount of data in sensors that are easily to be compromised. Even more, with the aid of the always-present sink, the network can defend against the attacks such as sensor compromises more efficiently and effectively. Nevertheless, due to the application restrictions, the above scenario is not always the case. In real world applications, there could be the cases where after the sensor deployment, the sensed data should be temporarily stored in the sensors because the sink is away from the network in most of the sensor network lifetime.