Sensors_**2010**, _10_, 8375-8397; doi:10.3390/s100908375  
_Sensors_  
**ISSN 1424-8220**  
www.mdpi.com/journal/sensors  
_Article_  
**Data Collection Framework for Energy Efficient Privacy Preservation in Wireless Sensor Networks Having Many-to-Many Structures**  
**[PERSON] \({}^{1,\star}\) and [PERSON] \({}^{2}\)**  
\({}^{1}\) Turkish National Research Institute of Electronics and Cryptology, Gebze, Kocaeli, Turkey  
\({}^{2}\) Faculty of Engineering and Natural Sciences, Sabanci University, Orhanli - Tuzla, 34956 Istanbul, Turkey; E-Mail: [EMAIL_ADDRESS]  
\({}^{\star}\) Author to whom correspondence should be addressed; E-Mail:[EMAIL_ADDRESS]; Tel. : +90-262-6481558; Fax: +90-262-6481100. _Received: 21 July 2010; in revised form: 3 August 2010 / Accepted: 3 August 2010 / Published: 8 September 2010_  
**Abstract:** Wireless sensor networks (WSNs) generally have a many-to-one structure so that event information flows from sensors to a unique sink. In recent WSN applications, many-to-many structures evolved due to the need for conveying collected event information to multiple sinks. Privacy preserved data collection models in the literature do not solve the problems of WSN applications in which network has multiple un-trusted sinks with different level of privacy requirements. This study proposes a data collection framework bases on \(k\)-anonymity for preventing record disclosure of collected event information in WSNs. Proposed method takes the anonymity requirements of multiple sinks into consideration by providing different levels of privacy for each destination sink. Attributes, which may identify an event owner, are generalized or encrypted in order to meet the different anonymity requirements of sinks at the same anonymized output. If the same output is formed, it can be multicasted to all sinks. The other trivial solution is to produce different anonymized outputs for each sink and send them to related sinks. Multicasting is an energy efficient data sending alternative for some sensor nodes. Since minimization of energy consumption is an important design criteria for WSNs, multicasting the same event information to multiple sinks reduces the energy consumption of overall network. **Keywords:** privacy preserving data publishing; k-anonymity; wireless sensor networksIntroduction  
Recent technological advances produce low cost wireless sensors for observing many physical phenomena of the world like temperature, humidity _etc._ As wireless sensor technology takes progress, the missions of WSNs get complicated; they are used in human, enemy, habitat, structure or traffic monitoring applications. With the advent of wireless body networks, applications for health monitoring of patients outside the hospitals or home-caring of elderly people have been designed and implemented widely. Recent WSNs have begun to collect much more information than simple WSNs observing temperature or humidity value of an environment. In an addition to spatio-temporal information of an event, especially in object monitoring applications, other attributes of monitored objects are gathered by sensors. For example, traffic monitoring applications collect velocity, direction and size information of a vehicle. As the complexity of wireless sensor applications increase, structures of WSNs have evolved in order to meet the new application requirements. WSNs generally have many-to-one structure so that sensors collect event information from the area and send to a unique sink. Some recent sensor applications have begun to use many-to-many structure, which means that there exists multiple sinks in the deployed environment. WSN application may need to send the same event information to different sinks rather than a unique sink. For example, in a home-caring application for elderly people, information about the elderly person can be sent to a family member and a nurse at the same time. As the capability of WSNs improves, privacy preserving is becoming one of the major problems in these networks.