From: jdblair@nextsrv.cas.muohio.EDU
Date: Tue, 14 Dec 93 19:55:42 PST
To: pmetzger@lehman.com
Subject: Re: picture signatures
In-Reply-To: <199312150253.VAA25863@snark>
Message-ID: <9312150421.AA15749@ nextsrv.cas.muohio.EDU >
MIME-Version: 1.0
Content-Type: text/plain


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>
> Could someone please tell me why I would possibly want to sign a
> picture? All it proves is that I had it in my possession -- it says
> nothing at all about if its been hacked (and indeed, it can be hacked
> regardless of what one does). A digital signature on a picture is no
> better than a court oath saying "yes, I took this picture". The only
> time you might ever want ANYTHING digitally signed is if you have
> doubts as to its origin or if someone might deny having signed it. It
> doesn't do you any good vis a vis verifying origin of a thing.
>
> .pm
>

Why does anyone ever sign anything?  Why did I sign this?  The 
signature attaches the reputation associated w/ a particular key to
this particular block of data.  I can be certain that you will either
get exactly what I wrote, or no if what you recieved isn't.

You know this already.  The point is, attaching a signature to a
picture guarentees that a picture I create hasn't been modified w/o
people knowing that its changed since it left my hands.  My pictures
could have reputations attached to them without the use of
digital signatures.  This reputation could be used against me if a
picture is modified, and my name is still attached to it, but with no
verifiable digital signature similarly attached.

- -john
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------------------------------------------------------------------------------
John Blair <jdblair@nextsrv.cas.muohio.edu>              phone: (513) 529-4879
    Insert cool signature file that makes a trendy, yet bold and original
   statement about my cyberspace proficiency, then mentions that I'll send
   you my PGP public key if you want it, and you trust that I'm actually me.