Random Grid and Reversible Watermarking-Based On Verifiable Secret Sharing for Outsourcing Images in Cloud

A novel random grid and reversible watermarking based verifiable secret sharing scheme for outsourcing image in cloud is proposed in the paper. In the proposed scheme, data owner firstly embeds the hash value of the secret image into the secret image itself using reversible watermarking algorithm; then, watermarked image is divided into $n$ sub image. Secondly, the hash of n sub image is calculated, and then the hash value is transformed into the initial value of hyper-chaos, thus n random grids are generated by different hyper-chaos. Lastly, after expanding the sub-image to the same size with the original secret image, it is performer XOR operation with the corresponding random grid, this will accordingly produce $n$ sharing secret. In order to securely outsource the image in the cloud, the generated shares are issued to the $n$ different cloud server. For authorized user, (s)he can get shares from different cloud server, and then can recover the original secret image through a series of decryption operations and extraction of reversible watermarking. The proposed scheme can losslessly restore the original secret image, and have the double verification ability, that is to say, it can verify whether the anyone of the sharing is modified, and it can also verify whether the original secret image is completely reconstructed. Some analysis and comparisons are given to show the security and effectiveness of proposed scheme.