Image Authentication Based On Reference-data Sharing Mechanism

The advancement of network and multimedia technologies has been gradually making the multimedia data an important source from which people can acquire information.How to efficiently and safely protect such information is now being the hot spot in current studies.As one of the important branches of information hiding technology,digital watermarking is also an important measure to protect the intellectual property.By embedding the confidential information,known as watermark into the original information,its proprietary and integrity can be verified in order to protect against illegal copying or altering of the digital product.This paper proposes two efficient and effective digital watermarking algorithms for image tamper detection and recovery,which is also called image authentication algorithms,based on the reference-data sharing mechanism.First of all,this paper proposes a self-embedding fragile watermarking scheme based on variable recovery-data sharing in section 3.The generated watermark bits in each image block are composed of recovery bits derived from the interleaved,and scrambled MSB bits of original image and authentication bits derived from the recovery bits and MSB bits.Different from the reported methods using a fixed embedding mode,the proposed scheme has two types of embedding modes,i.e.,overlapping embedding and overlapping-free embedding,and uses variable numbers of MSB layers and recovery bits.One can choose an optimal embedding mode to achieve better quality of watermarked image and better performance of content recovery.Secondly,this paper proposes a new self-embedding watermarking scheme with hierarchical recovery capability for tampered image in section 4.The binary bits in the adopted MSB layers are scrambled and individually interleaved with different extension ratios according to their importance to image visual quality.The interleaved data,which are regarded as reference bits for tampering recovery,are segmented into a series of groups corresponding to the divided non-overlapping blocks,and then embedded into the LSB layers of blocks together with authentication bits of tampering detection.Because the extension ratios of MSB-layer bits are based on the hierarchical mechanism,the efficiency of reference bits is increased,and higher MSB layers of tampered regions have greater probabilities to be recovered than lower MSB layers,which can improve the visual quality recovered results,especially for larger tampering rates.Experiments are conducted on a large number of test images to demonstrate the two methods proposed in this paper,including the simulation of the image block missing in fading transmission channel and the malicious modification by adversary.Experimental results show flexibility and superiority of the schemes as compared with other reported methods.