Watermarking Based Research On Copyright Authenticity Of Digital Image

Recently, the quickly development of network technology makes digital imagesspread very easily, and the storage, transmission of image data are almost completedinstantaneously. At the same time, along with the increasing number of digital imagescirculating in the network, the piracy phenomenon has been more and more common.Protected images can be effortlessly copied and distributed through some simpledevices, without giving any proper compensation to the images copyright holders,which seriously infringed the interests of the images owners. Therefore, how toprotect the authenticity of the copyright of the digital images becomes the problemwhich people have to face.The earliest technology of protecting digital images’ copyright is cryptography.Encryption keys are send at the time when the image is transmitted, the receiver canonly decrypt the accepted images when knowing the keys. However, the disadvantage isthat once the user obtained the keys, he could be able to distribution the copy of theimage continually. Cryptography can only protect the images which are intransmission, but can do nothing with the images which have been decrypted.Because of the above limitations of conventional cryptography in protecting thecopyright information, researchers have proposed a reliable and novel technology forprotecting the images copyright--digital watermarking. The technique uses imageproprietary information or other specific information as copyright information, andthe information is hidden in the digital images, when dispute occurs, the imagecopyright can be confirmed by extracting the watermark information hidden in thehost image.Existing space domain watermark algorithm has many advantages, such as thehigh speed of execution, flexible operation, large watermark capacity, and etc. But,these algorithms are often fragile watermarking algorithms which can not be widelyapplied to the image copyright authentication field where higher robustness is veryimportant. In order to keep the advantages and improve the robustness of thesealgorithms, we proposed a robust watermarking algorithm of space domain based onthe SSIM and the least significant bit (LSB). Comparing with traditional spacealgorithms, the pretreatment scrambling operation is imposed before the watermarkembedding process, which improved the difficulty of tampering with the watermark content information effectively. In order to ensuring the quality of watermarkedimages, the algorithm combines with the principle of SSIM which fits thecharacteristics of human visual system very well. By applying DES encryption, wecan protect the security of the watermark extraction process effectively. Manyexperiments show that, the proposed algorithm has a better quality of watermarkedimage, it can resist a variety of conventional image processing effectively, we canreasonably say that this method is fully applicable in the field of copyright protectionof digital images.Another robust digital watermarking algorithm proposed in the paper is based onchaos encryption technology, Arnold transform and discrete wavelet transform.Encrypting the original watermark information using Arnold and Logistic mapping,which can effectively increasing the security of the algorithm. Select the max value ofHL3sub-band coefficients of wavelet transform coefficient matrix to complete thewatermark embedding process self-adaptively. In order to balance the watermarktransparency and the robustness of the algorithm, adaptively embedding strengthfactor is introduced by the complexity of the image’s texture. Experiments show thatthe proposed algorithm shows strong robustness when facing cutting or replacingoperations with different degrees. In the accidental attack experiments, the algorithmshows good ability of resisting the attacks of brightness increasing, decreasing, to acertain degree, it can resist JPEG compression with low quality factors and noise also,but with poor ability of resisting median filtering attacks, therefore, how to enhancethe algorithm’s ability of resisting accidental attacks more effectively becomes thedirection of further study.