Re: Signing pictures -- how hard, how long?

I think signing photographs and movie images is a difficult problem. Why? Because one flipped bit will completely screw up the hash function. Errors on these tapes happen rarely, but most video manufacturers aren't really going to bother worrying about occasional bit errors because they're usually invisible to the eye. Why waste all that extra effort on error correction if it's not worth the trouble. So signed photographs will also need to contain all of the error correction necessary and that will make them more expensive. This isn't any real cost on a general purpose machine, but it matters in some places.