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Re: on the nature of trust

Phillip M. Hallam-Baker wrote:
> >On Thu, 12 Feb 1998, Tony Bartoletti wrote:
> >
> >-> Ed,
> >->
> >-> I do believe that your definition of Trust (in the sense analogous to
> >-> Information Theory) is the most elegant and useful one, to repeat:
> >->
> >-> > Trust: "Trust is that which is essential to a communication channel
> but
> >-> >         which cannot be transferred from a source to a destination
> using
> >-> >         that channel"
> This definition would apply equally well to my modem.


> Also consider the following thought experiment. I establish an email
> correspondence with a person who I have never met before. Over the
> course of ten years my only means of communication with this person
> is through email. Is is possible to establish a property that corresponds
> to our term trust as a result?
>             Phill

There's no clear answer to that question, as it depends on the context in
which the trust is being applied.  Do you need some externally transferred
trust to believe that a given message comes from the same person you've been
dealing with for a decade?  Probably not, but you don't need much to make that
kind of a decision.

For example, Ed has a rather distinct style of writing and I'd probably be
able to recognize one of his messages even without the headers or the .sig.
But I can't be sure that someone isn't masquerading as Ed.

Without some externally transmitted trust, what we have is a kind of Turing
test for trust -- is it really Ed, or just an incredible simulation?  This
might be an easy question to answer in a trivial context, but I think that an
external trust channel would be needed in a situation of any significance.


 Marc Branchaud                                       \/
 Chief PKI Architect                                  /\CERT SOFTWARE INC.
 marcnarc@xcert.com        PKI References page:              www.xcert.com
 604-640-6210x227      www.xcert.com/~marcnarc/PKI/

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