Threshold changeable secret image sharing scheme based on interpolation polynomial

In previous (k,n) secret image sharing scheme, the threshold k is decided by dealer according to the security requirement, and this threshold value is fixed without considering the dynamic secure environment in future. In this work, we propose a novel threshold changeable secret image sharing scheme where the threshold value can be changed according to the changeable security requirement. In our scheme, each participant only needs to keep one initial shadow. When reconstructing image, the dealer decides the threshold according to security level. If the threshold is unchanged, any k or more initial shadows can recover the image; else if the threshold is increased or decreased, dealer publishes additional information, each participant update their shadows accordingly such that the threshold of updated shadows is changed correspondingly. The contribution of our work is that the threshold of shadows can be changed flexibly to satisfy the dynamic secure environment, and each participant only need to keep one initial shadows. The feature of threshold changeable makes our scheme more practical than previous secret image sharing in some complicated applications.