Seals (was Re: Anyone know what became of the Gaim-E Project?)

[David Shaw]

On Mon, Nov 03, 2008 at 10:23:08PM +0100, David Pic?n ?lvarez wrote:
> From: "Ingo Kl?cker" <kloecker at kde.org>
> "There's a slight problem with the seal analogy. The seal has to be
> broken before one can read the letter and once the seal has been broken
> it does no longer prove anything."
>
> I was referring to seals as in http://en.wikipedia.org/wiki/Seal_(device) 
> and not in the sense of closing a letter with glue. The kind of seals you 
> stamp on the letter (or other documents like laws) itself. It's true that 
> these seals could also be used to impress over a closed envelope and 
> assure confidentiality, so that once opened they could not be used to 
> verify again. That would be the equivalent of opaque signing, where you 
> encrypt first and sign later.

Rather offtopic, but I read an interesting paper on seals a while back
(I'm afraid I don't recall where offhand).  Seals never really assured
confidentiality.  A person who wanted to open a letter would just make
a mold of the seal, melt it free, read the letter and then re-make the
seal using the mold.

The countermeasure was to use multiple colors in the seal so that
melting it free would mix up the colors so the new seal wouldn't look
right.  The catch was that you'd have to send a drawing of how the
first seal looked using a different communications channel so the
recipient could compare...

David