Linear equation based visual secret sharing scheme

Chen has recently proposed a visual secret sharing scheme for gray-scale images [5]. Linear equations of Hill cipher are used to divide an image into sub-images and then the concept of random grid is applied to sub-images for construction of encrypted image. The scheme is easy to implement and can be applied for visual secret sharing. However, the scheme suffers from security issues. Although, the random grid is used as a second layer of security, it does not play any effective role during decryption. Secondly, even a crude guess of the coefficient matrix used in Hill cipher equations can reveal the secret. To overcome these drawbacks, a new scheme based on linear equation is proposed in this paper. Experimental results demonstrate that the method is effective and secure.