One reason that signing pictures could be useful is so that you could tell that a given picture came from, say, FoobarFoto Mark IV Camera Serial #32767, which lets you know that the photo was digitally retouched after it was taken. Yes, it's easy for someone to transform that into an unsigned picture, simply by twiddling a few bits (doing so at the end of the bitstream lets you minimize any corruption, btw), but you can at least be sure that a signed video or still picture was faked in real-space before digitizing it... and it's easier to detect those fakes, though reputable publications like the National Enquirer and the TV news programs showing exploding cars still have trouble on occasion :-) Bill # Bill Stewart NCR Corp, 6870 Koll Center Parkway, Pleasanton CA, 94566 # Voice/Beeper 510-224-7043, Phone 510-484-6204 # email bill.stewart@pleasantonca.ncr.com billstewart@attmail.com