Abstract: The adage “photos don't lie” is no longer reliable. The advent of digital editing tools makes it relatively easy to move, add, or delete features from photographs. Other digital content is similarly susceptible to alteration. This problem is at least partially overcome by providing a photograph with supplemental data. This supplemental data is below a threshold of human perception (e.g., is essentially invisible) yet can extend throughout the image. If a version of the image is thereafter encountered with the supplemental data missing or attenuated, the image is known to have been altered. By reference to such supplemental data, it is often possible to identify particular regions within the image that have been altered.