A Pixels Level Fragile Watermarking Algorithm Used For Image Authentication And Recover

Nowadays the computer network and multimedia information processing technology have been developed rapidly around the world, which makes the information accessing and sharing more convenient and quicker. Then more and more digital media spreads widely. The efficiency and the accuracy of the Information Representation have been improved significantly. However, new problems are produced by the new technology. Safe problems are growing more serious, such as manipulation of information, infringement of copyright, revelation of sensitive information, theft of state secrets and so forth. Tampering with information and illegal transmitting will cause considerable damage to the public's life. So it is emergent to deal with the reality problem of effective authentication and data-integrity protection. Accordingly, a new picture authentication technology which is based on digital watermark has been made out. It aims at authenticating pictures and protecting the data-integrity by technologies during the entire life cycle of digital productions.Authentication-watermark technology has many advantages in protecting the integrity and the reality of the multimedia. It has become the focal point of research and developed greatly. Authentication-watermark technology is produced by the combination of concealed communication and the traditional cryptography, involving communication theories, image-processing technology and cryptography theories. It is overlapping strongly.Some of the presenting blocking authentication-watermark systems are unable to resist the VQ attacks effectively. Some others have lower authentication location accuracy, although they have the capability of resisting the VQ attacks. They are failed to fulfill the requirements of the present-day social development.Accordingly, this paper discusses a Fragile Watermark Algorithm for the pixel-level image authentication location and reconstruction. The presenting blocking authentication–watermark system based on hash function is easy to be attacked by VQ attacks,collage attacks and estimated attacks, because of the security flaw, that the fix of watermark image W and generating key K, and unrelated blocks. To solve the problems, the algorithm adopts the blocking numbered and image location-based encryption key generation mechanism, and eliminates the unrelated attribute of blocks and the possibility of estimate encryption function, and can effectively resist VQ attacks, collage attacks, search attacks and so on. The algorithm is a pixel-level image authentication scheme, achieves an accurate authentication at tampered image and requires the feature of the formed function extremely sensitive for the change of input, so as to satisfy the requirement of accurate authentication. For this, this paper makes emulation on hash function and finds that the hamming weight of MD5 function is extremely sensitive for the change of input, which can satisfy the requirement of accurate authentication. This paper adopts the hamming weight of MD5 function to be the authentication function of authentication watermark. This paper adds a reconstruction watermark to reconstruct the tampered image. Nowadays the methods of reconstruct image are only three. The most useful method is reconstruction watermark based on redundant information, which makes the invisibility best and fulfils the requirement of reconstruction tampered image. So reconstruction watermark adopts the average gray information of torus automorphisms block and has an good effect at the invisible of watermark and tamper reconstruction. To clarify the practicality of algorithm, this paper implements a series of fragile watermark image authentication system so as to put in a usable condition.The algorithm of image authentication is consisted of three parts:(1)The algorithm of forming watermarkThis paper implements two watermarks information:①a authentication watermark, which is based on hash function, used for tamper location;②a reconstruction watermark used for tamper reconstruction. We implement a absolutely-fragile, which has an excellent effect of authentication testing, making use of the feature of the hamming weight of hash function, that is extremely sensitive for the change of input. By virtue of adopting the blocking numbered and image location-based encryption key generation mechanism, the authentication watermark is able to effectively resist attacks. The reconstruction watermark adopts the average gray information of torus automorphisms block and has an good effect at the invisible of watermark and tamper reconstruction.(2)The algorithm of embedding watermarkEmbedding algorithm adopts the famous spatial domain LSB algorithm, which embeds the watermark information into the 2bi+LSB of all the pixels of the original image. By replace the lsb to embed secret information, it is easy to used for image and audio file and is the most classic method in information hidding, which only needs to do little change and can hidden large information. The algorithm is easy to implement, and the ability of tamper location is accurate, and the effort of tamper reconstruction is well and the watermark is invisible, meanwhile is fragile at every tamper operation.(3)The algorithm of extraction and checking watermarkIn the process of image authentication, it is no need to reference primitive image and is a blind extraction algorithm. The extraction and checking of watermark is the reverse of the forming and embedding of watermark. The algorithm has a fast speed and a high accuracy in authentication. It is enable to reconstruct tempered block by the information of reconstruction watermark.This paper still discusses a series of fragile watermark image authentication system based on the algorithm, giving the design module diagram of embedding watermark and extraction and checking watermark. The embedding watermark module accomplishes early work of image authentication and reconstruction, which are the generation of watermark and the embed-operation of watermark. They include the preparation of image, the generation of watermark and the embedding of watermark. The extraction and checking watermark module accomplishes the extraction and checking of watermark, also include the reconstruction of tempered image. Simultaneously we give the system implemention process diagram so as to put in the practical application.