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In this paper, a robust hash technique for image content authentication using histogram is proposed. The histogram based hash techniques reported in the literature are robust against Content Preserving Manipulations as well as incidental distortion. The major drawback of these techniques is that, they are not sensitive to Content Changing Manipulations and also un-altered histogram image modifications. To overcome these drawbacks, we present a novel hash technique which divides the image into non-overlapped blocks and distributes histogram bins of the image block into larger containers based on the Partial Sum of pixel count of histogram bins. An intermediate hash is produced by computing the ratio of pixel count between two neighbouring containers. The intermediate image hash is obtained by concatenating intermediate hashes of image blocks. Finally, the intermediate image hash is normalized and randomly permuted with a secret key to produce a robust and secure hash. The results shows that, the proposed method performs better when compared to the existing methods against the Content Preserving manipulations. Besides, the proposed method is more sensitive to Content Changing manipulations as well as un-altered histogram image modifications. The performance results on image authentication indicate that, the proposed method has high discriminative capability and strong robustness.

The technology of Wireless Sensor Networks (WSNs) has become most significant in present day. WSNs are extensively used in applications like military, industry, health, smart homes and smart cities. All the applications of WSN require secure communication between the sensor nodes and the base station. Adversary compromises at the sensor nodes to introduce different attacks into WSN. Hence, suitable Intrusion Detection System (IDS) is essential in WSN to defend against the security attack. IDS approaches for WSN are classified based on the mechanism used to detect the attacks. In this paper, we present the taxonomy of security attacks, different IDS mechanisms for detecting attacks and performance metrics used to assess the IDS algorithm for WSNs. Future research directions on IDS in WSN are also discussed.

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