There is a vivid research on securely deliver a secret message by using a data hiding technique in digital images. However, most existing solutions of data-hiding need to encrypt secret data first, and embed the encrypt message into cover image, which is not promising any security once the embedding algorithm is leaked. In this paper, an efficient and adaptive data hiding scheme is presented which is based on a new reference matrix named secure reference matrix. The scheme is flexible enough to meet different data hiding capacities and image quality as needed, and we allow the reference matrix to be more secure since it is randomly generated each time and make it much harder for being attack with exhaustive manner by extending the possible solution. We give the detail protocol for our scheme and provide the practical test and performance analysis. Experimental results show that our scheme has a better flexibility and efficiency in embedding process, and the average value of Peak Signal to Noise Ratio (PSNR) for the stego-images which are generated by our scheme have a higher visual quality for different embedding capacities, and our scheme is more efficient compared with related work.

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Underwater localization is an important and fundamental part of the Underwater Acoustic Networks (UANs). The problem we must face is that radio waves and optical waves are heavily attenuated underwater, so acoustic signals become the most common form of communication. However, the speed of sound wave is not constant and will be affected by the environmental factors. The inaccurate sound velocity will have a serious impact on the traditional positioning results. Therefore, the symmetry correction based on least square estimation (SC-LSE) is proposed in this paper. SC-LSE mitigates the influence of the imprecise velocity estimation on the localization by means of a special symmetrical relationship. We consider a realistic case, where the actual speed of sound is uncertain and the unknown nodes may be moving. The simulation results exhibit that our algorithm can achieve good performance and is not sensitive to the change of sound velocity and node movement.

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