“there is simply no equivalent of the permanently archived, physically unique photographic negative. Image files are ephemeral, can be copied and transmitted virtually instantly and cannot be examined (as photographic negatives can) for physical evidence of tampering. The only difference between an original file and a copy is the tag recording time and date of creation – and that can easily be changed. Image files therefore leave no trail, and it is often impossible to establish with certainty the provenance of a digital image.”
– William J. Mitchell (The Reconfigured Eye, 1992)
