HaG: Hash graph based key predistribution scheme for multiphase wireless sensor networks

Wireless Sensor Networks (WSN) consist of small sensor nodes which operate until their energy reserve is depleted. These nodes are generally deployed to the environments where network lifespan is much longer than the lifetime of a node. Therefore, WSN are typically operated in a multiphase fashion, as in [1-3, 9-10], which use different key pools for nodes deployed at different generations. In multiphase WSN, new nodes are periodically deployed to the environment to ensure constant local and global network connectivity. Also, key ring of these newly deployed nodes is selected from their deployment generation key pool to improve the resiliency of WSN. In this paper, we propose a key predistribution scheme for multiphase WSN which is resilient against permanent and temporary node capture attacks. In our Hash Graph based (HaG) scheme, every generation has its own key pool which is generated using the key pool of the previous generation. This allows nodes deployed at different generations to have the ability to establish secure channels. Likewise, a captured node can only be used to obtain keys for a limited amount of successive generations. We compare the connectivity and resiliency performance of our scheme with other multiphase key predistribution schemes and show that our scheme performs better when the attack rate is low. When the attack rate is high, our scheme still has better resiliency performance inasmuch as using less key ring size compared to the existing multiphase schemes

Hash graph based key predistribution scheme for mobile and multiphase wireless sensor networks

Wireless Sensor Networks (WSN) consist of small sensor nodes which operate until their energy reserve is depleted. These nodes are generally deployed to the environments where network lifespan is much longer than the lifetime of a node. Therefore, WSN are typically operated in a multiphase fashion, where new nodes are periodically deployed to the environment to ensure constant local and global network connectivity. Besides, significant amount of the research in the literature studies only static WSN and there is very limited work considering mobility of the sensor nodes. In this thesis, we present a key predistribution scheme for mobile and multiphase WSN which is resilient against eager and temporary node capture attacks. In our Hash Graph based (HaG) scheme, every generation has its own key pool which is generated using the key pool of the previous generation. This allows nodes deployed at different generations to have the ability to establish secure channels. Likewise, a captured node can only be used to obtain keys for a limited amount of successive generations. We also consider sensor nodes as mobile and use different mobility models to show its effects on the performance. We compare the connectivity and resiliency performance of our scheme with a well-known multiphase key predistribution scheme and show that our scheme performs better when the attack rate is low. When the attack rate increases, our scheme still has better resiliency performance considering that it requires less key ring size compared to a state-of-the-art multiphase scheme

Tackling in-camera downsizing for reliable camera id verification

Media Watermarking, Security, and Forensics 2019The photo-response non-uniformity (PRNU) of an imaging sensor can be regarded as a biometric identifier unique to each camera. This modality is referred to as camera ID. The underlying process for estimating and matching camera IDs is now well established, and its robustness has been studied under a variety of processing. However, the effect of in-camera downsizing on camera ID verification has not yet been methodologically addressed. In this work, we investigate limitations imposed by built-in camera downsizing methods and tackle the question of how to obtain a camera ID so that attribution is possible with lower resolution media. For this purpose, we developed an application that gathers photos and videos at all supported resolutions by controlling camera settings. Analysis of media obtained from 21 smartphone and tablet cameras shows that downsizing of photos by a factor of 4 or higher suppresses PRNU pattern significantly. On the contrary, it is observed that source of unstabilized videos can be verified quite reliably at almost all resolutions. We combined our observations in a camera ID verification procedure considering downsized media