Abstract: A digital image is "watermarked", that is, authenticated by an embedded pattern. The pattern is created by hashing the image and adding a signature element. Manipulating this result by the seed for a random number generator leads to an initial two dimensional random black-and-white pattern. This pattern is manipulated by a cellular automaton and smoothed before being added to the original image. To determine whether the image is authentic, one retrieves the watermark by subtracting the watermarked image from the original to obtain the difference. The value of the correlation between the difference thus obtained and the smoothed pattern determines the presence or absence of the watermark.

Abstract: A method of encryption features the steps of first encrypting a message and then hiding (embedding) it within a digital image carrier. This is accomplished by only slightly changing the gray levels of the image carrier. The changes are imperceptible to the human eye, because they appear as random thermal noise that is commonly present in digitized images.

Abstract: The present invention features a method for encrypting and decrypting large amounts of data such as images. A simple two-dimensional map is first generalized by the introduction of parameters. The generalized map is then discretized so that it maps a rectangular matrix of points (pixels in the case of image data) in a bijective manner. Finally, the map is extended to three dimensions to modify the gray levels. The parameters of the map then serve as a ciphering key. The encryption consists of several iterative applications of the map to a block of a plain text message such as an image. The encryption is such that the resultant image is uncorrelated and appears as static on a TV monitor in the absence of a signal. The resultant histogram of the enciphered image becomes essentially uniform. The enciphered data is deciphered by applying an inverse map an identical number of iterations. The inventive method provides both superior speed and improved security over previously used methods of encryption.