From: cman@caffeine.io.com (Douglas Barnes)
Date: Tue, 14 Dec 93 08:13:53 PST
To: wex@media.mit.edu (Alan)
Subject: Re: Signing pictures -- how hard, how long?
In-Reply-To: <9312141523.AA28906@media.mit.edu>
Message-ID: <199312141559.JAA07050@caffeine.caffeine.io.com>
MIME-Version: 1.0
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Actually, I was talking to someone the other day about this same
problem, and spun out approximately the same solution. The important
part would be a fast MD5 chip or equivalent (very fast algorithm) and
the camera would only periodicallly sign the result. 

The question in my mind is, "do you want to sign every N frames, or
only from the digital equivalent of a control track break to a control
track break."  (Obviously digital cameras don't have control track
breaks, but a certified one would need to create an equivalent.)

For use in legal matters, I'd assume you'd need to put seals on the
device, or something, that were periodically inspected, to make sure
the signal wasn't tampered with before hitting the signature module.
I'd imagine that you _could_ incorporate the cameraperson's key, but
more likely it would be some key issued by the certifying agency (a
very high-rep individual or organization) that inspected the camera
periodically, placed the seals, etc.

A problem I see: highly realistic projections might outpace camera
tech, so that you could just be projecting something and recording it.
Might be thwarted by inclusion of a GPS inside the sealed part of
the module.

I was reading David Brin's _Earth_, and one of the things he posits are
these legions of senior citizens with TruVue (or something) glasses
that are apparently certified for crime reporting.

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