Reversible secret image sharing based on Shamir´s scheme with discrete haar wavelet transform

We proposed a fast secret image sharing based on Haar wavelet transform and Shamir´s method. Many researchers develop secret image sharing method with Shamir´s algorithm in one whole image. We employ discrete Haar wavelet transform to reduce the secret image to its quarter size firstly, i.e. the 1-level LL subband. Then only apply the modified Shamir´s algorithm to this LL subband to generate the shadow images. Lagrange method exploits the enough numbers of the shadow images in the retrieval step. Due to the Shamir´s and Lagrange algorithms consume a lot of time during the processing of the secret image sharing. Our method only processes a quarter size of image that can decrease computation time, and still achieve to recover the secret image reversible. The experiment results demonstrate our method is fast and retrieve secret image lossless.