Abstract: A method of encoding a graphical message (220, 221) based on a key sequence as an encoded sequence of information units. For each pixel of the message, said pixel having a normalized intensity I, a total rotation ? which results in a liquid crystal display in a pixel with substantially the intensity I is determined. The key sequence contains arbitrary rotations. The difference between the total rotation a and a corresponding rotation in the key sequence is output as an element of the encoded sequence. A device (201) presents pixels with rotations indicated by the encoded sequence on a first display (701) and pixels with rotations indicated by the key sequence on a second display (211). Superimposing the two displays reveals the graphical message. The method can be repeated for red, green and blue intensities of color pixels, allowing colored graphical messages to be encoded and reconstructed.

Abstract: A method of visually encrypting a graphical message (100), in which a first share (110) is produced based on the graphic message (100) and a key sequence, the method comprising inserting a filler in a monochromatic area of the graphical message (100) before producing the first share (110). The filler may represent a regularly spaced grid, a pseudo-random pattern, a predetermined graphical image or, in case of a color message, a colorful background. Also a device (500) and a computer program product arranged for carrying out the method.