Signature without policy meaningless? (was Re: UI terminology for calculated validities)

[Nicholas Cole]

On Sat, May 3, 2014 at 8:54 AM, NdK <ndk.clanbo at gmail.com> wrote:
> Il 03/05/2014 01:10, Daniel Kahn Gillmor ha scritto:
>
>> Having such an assertion cryptographically bound to the OpenPGP
>> certificate in parseable form implies in some sense that you think a
>> mechanical process (e.g. WoT calculated validity) should be able to make
>> use of it.  But how would that work?
> Making WoT calculator avoid looking for keys signed by that user if
> reached throught my certification.
>
>>  It sounds like you'd want to ask
>> an OpenPGP to introduce an additional concept on top of the notions of
>> validity and ownertrust (which are already confusing):
> They work: I'm *really* confused. :)
>
>> some sort of meta-ownertrust: instead of ownertrust's question of:
>> "how much am i willing to rely on NdK's identity assertions",
> Well, if ownertrust answers that, it's what I need: a way to say "I am
> sure this key belongs to X, but I don't want it to be used to introduce
> more keys in the WoT".

But it doesn't work like that anyway.  Unless you are using Trust
signatures (and few people do) then a signature on a key does not
encourage a 3rd party to trust signatures made by that key.

Even if a key is recognised as authenticated/validated/certified for
association with a particular email address, the signatures made by
that key will not be trusted by anyone who has not made an active
decision to make a particular key a trusted introducer.

In fact, this is a reason (though one of many) why the web of trust
has never quite lived up to its promise.  No UI that I am aware of
sets even marginal trust by default on newly imported keys.  Most
users (I suspect) will only ever end up trusting keys that they
themselves have signed.  That is the default position.

It is interesting to speculate whether the WoT would have been more
effective if there had been a culture of marginally trusting new keys
by default, allowing users to make an active choice either to not
trust someone or to fully trust someone.  As it is, the inertia of the
system works against the idea of a web of trust.[*]

In any case - there is no need for what you are suggesting.  3rd
parties are not (by default) going to infer from your signature that
they should then trust the key you sign as an introducer.

N.



[*] I'm aware there are problems with "marginal trust" related the
fact that the requirement of three marginally trusted signatures to
confer validity may in fact be fairly weak. The three signatures may
not, in fact, be made independently of each other (consider three keys
owned by the same person which all introduce a third key, for example,
or multiple signatures made a single key-signing party).