[Freedombox-discuss] Relationship driven privacy

Daniel Kahn Gillmor dkg at fifthhorseman.net
Thu Jul 7 20:26:49 UTC 2011


On 07/07/2011 02:36 PM, The Doctor wrote:
> You can sign a pseudanonymous key and publish it.  What you have to be
> cognizant of, however, is the trust level of the pseudanonymous key (set
> when the public key is signed), which ranges from 0 (no trust at all) to
> 5 (trust fully).

Urgh, this is not the case.  Normal OpenPGP certifications do *not*
contain any indication of trust.  GPG stores *private* ownertrust levels
for each public key in its keyring.  The user in control of the keyring
gets to decide which keyholders to rely on for identity certification,
and can change those decisions at will.

> That metric goes into the list of signatures a public
> key has picked up,

Again, standard public OpenPGP certifications do *not* contain any
indication of trust.  Private decisions about ownertrust are factored
against publicly-(or privately-)stated certifications of identity.  But
the identity certifications do *not* contain trust information.

> ("I know that key really belongs to J. Random Activist because the
> following six dozen people I have some trust in know that the keypair
> belongs to a fellow activist.") 

This is exactly right; in this scenario, the "trust" is a privately-held
piece of information ("people i have some trust in"), and the
certifications simply say "i know that this key belongs to the person
identified by the User ID".

> ("Not many people trust that this public key really belongs to J. Random
> Activist; maybe it belongs to an impostor.  I won't trust that key or
> use it to contact that person.")

This is subtly mistaken, i think.  it's not "not many people trust that
this public key belongs to...", but rather "no one *who i trust* has
stated that this key belongs to..."

That is, the certifiers are stating knowledge of identity and key
ownership, not trust.

The *evaluators* of the OpenPGP certificates get to decide which
certifiers they're willing to rely on (or "trust").  But the evaluators
make these trust decisions privately, and independently of doing any
certifications themselves.

hope this helps clarify things,

	--dkg

PS there is such a thing as a "trust signature" in the OpenPGP spec, but
it is extremely rare in practice, and should probably remain so.
Separating identification from trust has many nice properties that we
shouldn't throw away.

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