EFFICIENT COMPRESSION AND ENCRYPTION SCHEME FOR SECURE TRANSMISSION OF IMAGES AND ITS RECONSTRUCTION

When it is desired to transmit redundant data over an insecure and bandwidth-constrained channel, it is customary to first compress the data and then encrypt it. In this paper, we investigate the efficiency of reversing the order of these steps, i.e., first encrypting and then compressing, without compromise for compression efficiency or the informationtheoretic security. A pseudorandom permutation and a linear encoding scheme is used to encrypt an original image, and the encrypted data are efficiently compressed by discarding the excessively rough and fine information of coefficients generated from orthogonal transform. After receiving the compressed data, based on spatial correlation, a receiver can reconstruct the principal content of the original image by iteratively updating the values of coefficients and the linear decoding procedure