Re: What real users think [was: Re: pgp signing in van]

[Dave Crocker <[e-mail]>]

On 9/9/2013 1:27 PM, Steve Crocker wrote:
> Actually, I interpret the chemistry professor's comment in a
> different light.  It would be possible to design a system where:
>
> o the standard end user software doesn't facilitate editing the other
> person's text, and
>
> o each piece of text is signed.
>
> The result would be a system where a recipient would know whether the
> person who is alleged to have written a piece of the message actually
> did so, and the normal mode of use would be to leave things
> untouched.  Or, if you edit someone else's text, it immediately
> becomes your text.


The professor's comment was on function, not method. My comment was on
the limitations to methods available at the time.

In a controlled environment, with good resources, quite a bit is
possible. Indeed, server-based "department-level" email products in the
1980s did enforce such restrictions. The single-administration servers
had complete control over the message.

Distribution with independent administrative authorities makes this a
very different game. Enforcement by fiat is impossible.

That's where signing comes in, of course. Modify the content and the
signature fails. Besides the computational overhead -- which was
relatively onerous back when the infrastructure was being established --
this requires that the receiver know and demand that the signature be
present; this requirement has its own adoption barriers.

Starting with a blank sheet and today's technologies, the requirement is
possibly feasible to satisfy -- if we ignore the continuing human
factors barriers to large scale email authentication. However given the
resources at the time the operational service was developed, I think it
wasn't.


d/
-- 
Dave Crocker
Brandenburg InternetWorking
bbiw.net