Image Hashing Algorithm Resistant Against Geometrical Attacks

With the rapid development of the internet and digital multimedia technology,the storage,processing and distribution of the digital multimedia products become more convenient and efficient.This situation brings a lot of convenience to people,but also raises the worries about its safety and authenticity.Image is regarded as a major part of the multimedia information.When the image is transmitted on the internet,it will go through some conventional attacks such as JPEG compression and etc.So it is very important to propose some efficient method for the image authentication.The traditional hash function usually extract short bit string from large number of digital information as the message digest.The traditional hash function is very sensitive to the input data,even a small bit change will result in large changes in the hash result.But the image will undergoes various processing when it is transmitted.So a new image authentication technology is proposed---image hashing,which provides a new solution for image identification and authentication.This paper not only introduces the research background and significance of the image hashing,but also summarizes the construction of the image hashing and analyzes the advantages and weaknesses of different algorithms,and also solves the problem of resisting geometric attacks.This paper mainly concludes the following works:(1)A robust image hashing method based on LPM and Contourlet transform is proposed,which can resist against geometric attacks.The log-polar mapping(LPM)and contourlet transform are employed to obtain the low frequency sub-band image.Then the sub-band image is divided into some non-overlapped blocks,and low and middle frequency coefficients are chosen from each block after discrete cosine transformation(DCT).The singular value decomposition(SVD)is applied in each block to obtain the first digit of the maximum singular value.Finally,the features are scrambled and quantized as the safe hash bits.Experimental results show that the algorithm is not only resistant against common image processing attacks and geometric distortion attacks,but also discriminative to content changes.(2)A robust image hashing algorithm based on radon transform and invariant features is proposed,which can well distinguish malicious tampering images and different content images.The standardized image preprocessing is carried out on the image.The invariant centroid algorithm is applied to obtain the invariant feature points and the circular areas around.The radon transform can be used to the areas for getting the mapping coefficients matrix.Finally the hashing sequence can be generated by combining the local features and global features extracted from radon domain.The algorithm takes advantage of the chaotic systems to ensure the security of the algorithm.The Euclidean distance is applied to compute the similarity between two hash sequences.The experimental results show that the algorithm not only owns good performance of resisting against some common image processing,but also some geometric attacks such as rotation,translation and etc.Finally,this paper summarizes all the works and discusses the shortages and main issues of the image hashing field,and also presents the deep research orientation of image hashing in the future.