METHOD AND DEVICE FOR COMPRESSING AND EXPANDING IMAGE INTENDED FOR ENCRYPTED COMMUNICATION, PROGRAM, AND STORAGE MEDIUM

摘要

The present invention addresses the problem of providing a method and device that solve the problem of the inability to compress and transmit a digital image without a loss while encrypting the image, to expand the image on the reception side, and to restore the digital image in an artifact-free state. The present invention also addresses the problem of providing a program and a storage medium therefor. An image or video is encrypted by subjecting an encryption key image to discrete convolution, thereby obscuring the image or video beyond recognition. The image or video is further entropy-encoded and losslessly compressed for transmission over the Internet. After being expanded on the reception side, the pre-encryption image is decrypted by performing iterative calculation on the basis of the Bayes probability formula using the separately delivered encryption key image.