Multicasting Secret Images using a Knapsack-like Cipher System

摘要

In this paper, we have proposed a method to deliver images in a multicast system. In our scheme, a pre-generated codebook was used to encode the hidden image, before delivery and broadcasting within a network system. After the encoded message associated with the hidden codebook has been received, only the intended recipients can recover the original message, according to the codebook recovery procedure. This image encoding uses vector quantilization, where all pixel blocks of an image's vector representation are encoded with corresponding indices; each index is associated with the closest codeword in the pre-generated codebook. Rather than delivering the original image, this set of image indices are transmitted to the network. The original image can only be obtained if the hidden codebook is revealed. In this scheme, this crucial codebook is encrypted, using a knapsack-like cipher system, and can only be decrypted by the intended recipient based on a combination of the public-system and a secret sharing scheme. Security considerations are based on both the intractable cryptanalysis of Shamir's (t, n)-threshold scheme and a discrete logarithm over GF(p). Thus, it is secure and efficient in broadcasting multimedia, and requires less space, when being transmitted to a group of intended receivers in a network system.