An image encryption method that includes receiving image data based on an image, wherein the image data comprises a plurality of pixel values, and permuting a plurality of, and preferably all of, the pixel values using at least a secret key to create permuted image data. Also, an image decryption method that includes scanning a printed image to create scanned image data. The printed image is generated from permuted image data that is generated by permuting a plurality of first pixel values of first image data using at least a secret key, obtaining a plurality of second pixel values from the scanned image data, and reverse-permuting a plurality of the second pixel values using at least the secret key to create reverse-permuted scanned image data.