An Authenticated Key Agreement with Rekeying for Secured Body Sensor Networks Based on Hybrid Cryptosystem Noor ul Amin Hazara University Mansehra, Pakistan namin@hu.edu.pk Muhammad Asad International Islamic University, Islamabad Pakistan m.asad@iiu.edu.pk Nizamuddin International Islamic University, Islamabad Pakistan sahibzadanizam@yahoo.com Shehzad Ashraf Chaudhry International Islamic University, Islamabad Pakistan shahzad@iiu.edu.pk Abstract— In recent years personal health monitoring Body Sensor Network (BSN) have got significant importance. Due to its sensitive and constrained nature, health data should be transported / kept confidentially, therefore, lightweight cryptographic technique and key management schemes are required in BSN. In this paper we have proposed a hybrid authenticated key agreement with rekeying for Body Sensor Network. Our scheme is based on Symmetric and Elliptic Curve Cryptography. The proposed scheme reduces seventy four percent memory requirements for keys storage, eighty seven percent Computation Cost and sixty one percent Communication Overhead. Keywords- Session Key; Elliptic Curve Cryptography; Body Sensor Network; Rekeying; I. INTRODUCTION . Development of sensors brought the world with new technological changes and new research areas evolvement in this domain. Communication of information through sensor nodes gave birth to Wireless Sensor Networks (WSNs). Sensing its environment and then transmission amongst sensor nodes unveiled several new exciting life–sustaining applications of patient health care, patient monitoring and providing medical solutions wirelessly. In WSNs, data is communicated over Wireless Channels, so we need to put some security measures and ensure secure transmission of information. Characteristics, properties and behavior of human body are very dynamic. Sensors designing, development then deployment should be given prime attention and special features should be added. Tiny, lightweight, wearable, stitchable and cheap sensors are required for all health care systems. These are special purpose sensors designed to cope with all dimensions of human body’s sensitivity i.e. pulse, heat, blood pressure, sudden reactions etc. Sensors deployed on human body collect sensed data, process sensed data, communicate it with each other and then transmit information to Base Station (BS) which in turn updates these information. Base station consists of processor units, high memory with computational power; used to control all sensors deployed on body and interact with external nets. External net composed of medical servers where patient data is stored. Medical doctors/physicians access these servers for generating medical reports of the patients as and when required. Security measurements are essentials for BSN as it has distinct features, techniques and framework than that of implemented for WSNs which are not feasible for BSN. Serious security challenges may be faced as highly sensitive natured data is transmitted amongst bio medical sensor nodes. BSN security and information protection has not been investigated properly in depth before, so it opens a gate for researchers and provides opportunity of research in this area. In comparison with Generic WSNs, BSN requires such security solutions that would provide better security, less storage space and low energy consumption than that of WSNs. Key Management plays pivotal role in the security of Communication Protocols. The existing techniques presented in the literature for key agreement, either only symmetric key technique is applied where problems of security and scalability occur or only public key technique is applied where high cost is the prime issue. We have used hybrid approach which combines both of the techniques in such a way that eliminates the negative aspects of both of the schemes. II. LITERATURE REVIEW In proposed scheme [1], a secret key is preloaded which is shared amongst all nodes involved in communication. For further communication secret key is generated through Cryptographic Protocol for a specific session. This scheme is of use where huge deployment of sensors and monitoring is required; it is static and non-scalable mechanism. This scheme can’t be used for an environment of dynamic nature or updating and recollection of membership. In proposed technique [2], public key cryptographic infrastructure is used for the security of shared secret key amongst nodes. Symmetric session keys are distributed though public key. Here symmetric keys distribution is applied for Key Management which leads to high cost. High cost of the proposed technique restricts it to be fitted in BSN. In [3], biometric technique is used for key distribution while using bio channels. Sensor nodes are linked through bio channels on human body which are used for key exchange. Bio-channels link sensor nodes on human body which are used for keys exchange. Any bio channel can be borrowed for key management out of these channels. Generation of random keys through bio-metric system is a problem due to dynamicity of multiple nodes. 118 978-1-4673-0390-3/12/$31.00 ©2012 IEEE