The Jamming-style Denial of Service (J-DoS) attacks are significant causes of malfunctioning of Wireless Sensor Networks (WSNs). The nodes of WSNs are prone to external disturbances especially when they are used in hostile environments. The attackers mainly operate in the wireless communication medium by following a couple of diverse scenarios. In this paper, we have developed two detection mechanisms used for J-DoS attacks in order to differentiate the legitimate and adversary scenarios. The detection mechanisms designed utilize some network parameters and additional packets to separate and classify normal conditions and adversary ones. Having detected the type of the attacker, appropriate counter measures can be applied.

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The main purpose of the digital watermarking is to provide information security and copyright protection. From this point of view, a robust blind watermarking method based on Discrete Cosine Transform for colour images is proposed in this paper. The proposed method provides hiding a binary watermark in a compressed Digital Colour Image. First, the Digital Color Image is transformed into YCbCr from RGB color space and then the Discrete Cosine Transform middle band of the luminance (Y) component is used for watermarking processes. Each bit of the binary watermark is embedded in a different Discrete Cosine Transform block. Thus, deterioration on the image is minimized achieving high invisibility. The situation is checked whether the watermark is lost after the image saved. If the watermark is lost in any block, the average of some neighbouring Discrete Cosine Transform coefficients is used for embedding the watermark bit. The experimental results show that the proposed method can be safely used when point of interest is binary watermarks. Moreover, extraction processes do not need the cover image and the watermark is recovered completely. Statistical and perceptual quality evaluations show that the proposed method is better than its counterparts.

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