From: wcs@anchor.ho.att.com (bill.stewart@pleasantonca.ncr.com +1-510-484-6204)
Date: Wed, 15 Dec 93 00:40:32 PST
To: cypherpunks@toad.com
Subject: Re: signing pictures
Message-ID: <9312150840.AA19706@anchor.ho.att.com>
MIME-Version: 1.0
Content-Type: text/plain


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