Research And Implementation Of Distributed Digital Watermarking Algorithm In Wireless Sensor Networks

To protect the reliabity, integerity and freshness of the data collected from the networks is crucial for wireless sensor network whose main task is to sense data of the circumstance,for the reason that the data probably be modified by an invader as this network is always deployed in hostile areas.Watermarks embedded into sensor datas of wireless sensor network as an identity of generator would change along with data transformation and shall be detected by an application system to determine the reliability and integrity of the data. According to the quality of distributed data sensing and processing on single nodes in wireless sensor network, this paper mainly does research on distributated watermarking algorithms and the implementations, which are suitable for wireless sensor network.The main work is as follows:(1)Usually, the current data authentication in wireless sensor network shall append several message authentication codes to the data packet, which have a high computational complexity and enery consumption.In this paper, a negotiation-based digital watermarking for wireless sensor networks is given.Clusters with dense nodes in WSN are divided into groups,and nodes of the same group consult the watermarks that will be embedded into the sensing data. Each node embeds watermark bits into sensor data by modular operation. The analysis and experiments show that the watermarks are robust against loss data process while fragile to invalid modification by an invader, which could distinguish the false data and invalid data modification.(2)In reality applications such as military, high constraint of data integerity are always demanded of, and the data must be recovered after security authentication, thus we propose a reversible watermarking based on difference expansion algorithm to satisfy the requirement of data recovery. Especially, several technique against the open space of the network deployment and resource constraint of single sensor node have been made;The whole watermark is split into a number of segments that shall be randomly assigned to sensor node in order to enhance the ability to resist collusion attack, which might get the watermark by comparing data. Meanwhile,the data fresh problem is resolved through a pair of synchronous random number generator kept by both sensor node and sink separately.(3)Based on the above achievements,a watermark emulator using OMNeT++ simulation software is designed and implemented.Nodes of the same group generate watermark by negotiation, and forward sensor datas to base station for detection.The experiment shows that the watermark emulator could authenticate the integrity and reliability of data in which watermarks was embedded by sensor nodes,thus enhence the safety of data. In the end,we have implemented a watermarking prototype system in TinyOS as well.The prototype system could collect temperature and luminosity of the surroundings where sensor nodes are located.Each single node of the network could embed watermarks into its data which will be detected later by the network terminal PC,and forward data packet to base station via cluster header.