[cap-talk] Delegating Responsibility in Digital Systems: Horton's "Who Done It?"

Sandro Magi smagi at higherlogics.com
Thu Jun 7 12:31:19 EDT 2007

Jed Donnelley wrote:
> At 07:22 AM 6/7/2007, Pierre THIERRY wrote:
>> Wasn't providing undeniable authentication a motivation of the
>> discussion that led to the design of the Horton protocol?
>> Curiously,
>> Pierre
> I'd also like to see an answer to the above, partly in the hope that
> it might help to clear up the other high level issues that I'm
> struggling with.
> What meaning does 'responsibility' have if it is deniable?
> For example, going back to something that James Donald wrote
> (that I've now of course read many times):
> "Let us suppose we manage to get in place an email system
> where all email is authenticated by a public key, but
> not signed by a public key - that is to say, the
> recipient knows what key it came from but cannot prove
> this to others.  We assume entities are ultimately
> identified by their key, not by a "true name" that is
> somehow bound to the key."
> Can somebody (other than James I guess, since he's
> frustrated by trying) explain to me what the above means?
> As I understand things, nothing can be "signed by a
> public key", only by a private key.

I take the above to mean: the e-mail was sent over a channel encrypted 
by the public/private keys (so the recipient knows who it came from), 
but the message itself is not digitally signed by those keys (so the 
recipient cannot prove who it came from to anyone else). The encryption 
is only involved during message transmission.


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