Reversible secret image sharing scheme in encrypted images

The previous secret image sharing schemes did not provide a copyright and privacy for cover images. The reason is that a dealer selects a cover image by itself and embeds directly the secret data into the cover image. In this paper, a reversible secret image sharing scheme in encrypted images is proposed in order to provide the copyright and privacy of the cover image. We divide a role of the dealer into an image provider and a data hider. The image provider encrypts the cover image and transmits the encrypted image to the data hider, and the standard stream cipher as one-time pad (OTP) with a random secret key is used. The data hider embeds the secret data into the encrypted image, and the encrypted shadow images are transmitted to the corresponding participant. We utilize the polynomial arithmetic operation over GF(28) during the sharing of the encrypted shadow images, and the coefficient of the highest-order term is fixed to one in order to prevent the overflow and the security problem. In the reconstruction procedure, the secret data can be extracted and the cover image can be reconstructed exactly from t or more encrypted shadow images with Lagrange interpolation. In experimental results, the proposed method shows that the PSNR is sustained close to 44 dB regardless of the embedding capacity, where the embedding capacity is 524,288 bits on average.