Copy-paste tampering is one of the most common image content attacking methods. Considering the low accuracy and high feature dimension of the existing algorithms, a normalized moment of inertia method is proposed in this paper to overcome these defects. In the phase of feature extracting, the algorithm first transforms the tested image using wavelet, and then selects the similar subbands to build overlapped blocks, finally uses Perceived Hash Algorithm (PHA) to make binarization processing for the subblocks and carries out the normalize moment of inertia of the subblocks which satisfy the coarse matching conditions between adjacent two lines after performing dictionary sorting. In feature matching phase, the algorithm first counts the similar subblocks whose shift is above the distance threshold, and then obtains the main shift vectors with specific frequencies, finally performs feature matching according to the difference of the normalized moment of inertia in the neighborhood. Experiment results illustrate that the proposed algorithm with lower feature dimension can efficiently improve the matching speed and accuracy. Furthermore, it has better robustness for some post-processing operations, such as compression, Gaussian Blur, adding Gaussian noise, etc.

The physical properties of water lead to attenuation of light that travels through the water channel. The attenuation is dependent on the color spectrum wavelength, that results in low contrast and color cast in image acquisition. Several methods have been proposed to handle these problems, such as Linear Stretching, Histogram Equalization (HE) and their variants. Considering the advantages of HE and Linear Stretching, this paper presents a new Adaptive Linear Stretch method (ALS) which can efficiently improve the subjective impression of the traditional Linear Stretching and keep the computational cost low at the same time. To achieve adaptability, the adaptable threshold is deduced from the histogram of image. Performance analysis reveals that the proposed method significantly enhances the image contrast, reduces the color cast and meanwhile, keeps the computational consumption low.

In distributed networks, the signer wants his signature to be verified by anyone in the same group with him and the recipient wants to verify the signature independently. Motivated by this consideration, a certificateless group inside signature is presented in this paper. The signature scheme has the following properties: despite being without certificate, it can provide an assurance to the user about the relationship between a public key and the identity of the holder of the corresponding private key; a signature can be verified independently by any member in the same group with the signer; nobody outside the group can verify a signature. It is only the signer who knows his private key, even the PKG (private key generator) doesn't; any one in or outside the group can't forge a signature of others.