Study On Reversible Data Hiding Algorithm For Encrypted Image

With the rapid development of multimedia technology and computer networkcommunication technology, more and more digital information has been transmittedthrough the network, digital image is widely used due to its vivid and intuitive features.However, there are some security problems in the transmission, such as the informationis easy to be stolen, tampered, replicated maliciously at any time. Therefore, how toensure the transmission security of digital images, especially, the ones withconfidentiality and privacy has become an urgent problem.In recent years, there are many technologies sprung up in academics, encryptionand data hiding are two fruitful branches of it. Most scholars use one of them to ensurethe security of information transmission. However, some applications in reality need tocombine encryption with reversible information hiding technique to solve practicalproblems. For example, medical images should be encrypted for protecting the patient’sprivacy, a database administrator may aim to embed the personal information into thecorresponding encrypted images. The traditional methods are not able to meet thephysical requirement, such as encryption and information hiding are separate, thealgorithm is irreversible, the embedding capacity is small, etc. In this paper newschemes are proposed to solve the above problems. Digital images are widely usednowadays, researching and designing encryption and information hiding algorithm hasan important theoretical and practical significance. Some contributions accomplished inthis paper are as follows:Firstly, the classical algorithms of image encryption and the reversible data hidingare studied at great length. Then, analyze the flaws of the existing algorithms whichcombine the encryption technique with the information hiding technique.Secondly, combining scrambling encryption algorithm with the reversibleinformation hiding algorithm based on improved histogram modification, a newreversible information hiding algorithm in encrypted images is proposed in this paper.At first, divide the image into several blocks, scramble each block, and then selectmultiple points of each block to embed, meanwhile the process can be repeated severaltimes. The simulations on MATLAB indicate that the algorithm has a high embeddingcapacity, and the decrypted image is still with good quality. This algorithm is easy to beimplemented and the operating sequence in the receiving terminal is flexible. Thirdly, Based on substitution cryptography algorithm, the MLSB algorithm andthe invariance of xor operation, a new algorithm with separation mechanism is proposed.At first, divide the image into several blocks, and then encrypt each block by apseudorandom number, finally embed information by flipping MLSB of pixels. Thesimulations on MATLAB indicate that the algorithm has a high embedding capacity,meanwhile the distortion of image is small. What’s more, the operation sequence inreceiving terminal is flexible, meanwhile it meets the requirement of separationmechanism.