[foaf-protocols] Multiple URIs in SAN extension

Melvin Carvalho melvincarvalho at gmail.com
Sat Aug 14 17:22:42 CEST 2010

On 5 August 2010 18:55, Stéphane Corlosquet <scorlosquet at gmail.com> wrote:

> Hi,
> The WebID spec does not currently cover the case where there are more than
> one SAN URI entry in the same certificate. Do we have scenario where this
> would be useful?
> In a typical WebID authentication workflow, if your WebID provider is down
> for some reason, then you cannot authenticate with your WebID (leaving aside
> the particular cases of caching and trusted data sources). If your
> certificate contained another WebID URI, the Verification Agent could then
> dereference this other WebID URI to attempt authentication (provided the
> same public key was published at the second WebID Profile Document as well).
> The problem though is to know what your WebID URI is once you've
> authenticated via an alternate WebID URI. Should the Verification Agent
> trust that you are WebID URI #1 when the authentication sequence via WebID
> URI #1 didn't work and only WebID URI #2 worked? Clearly no, unless you can
> prove that you also own WebID URI #1 by having logged in via this URI in the
> past (in which case the Verification Agent would merge the two identities).
> Is this a good use case to justify the use of multiple WebID URIs in the
> same certificate? It would be equivalent to having to separate certificates,
> but the great advantage is that from user point of view you just have to
> choose one identity, however many WebID URIs you have associated with this
> identity (and you're pretty much sure at least one of your providers/servers
> will be up).
> <side-note>This raises a related issue. If we expect WebID to take off and
> to be easy to publish your own WebID, there ought to be ways to work around
> the fact the servers go down, that's one reason why there are so few OpenID
> providers and they are all big players providing decent QoS. In the case of
> WebID, even if you choose the best software implementation you can find on
> the market, you're still dependent on your hosting provider. WebID
> provisioning should work on cheap hosting to be truly decentralized avoid
> the same centralization OpenID has.</side-node>
> Do we have other scenario where it is useful to have multiple URIs? There
> might be cases where a URI entry of the SAN extension is not meant to be a
> WebID (think other protocols sticking a URI in a certificate like we do).
> This might be fine and play nicely with the above scenario as long as the
> Verification Agent tries the authentication sequence with each URI entry
> until it finds a matching public key in whatever document each URI
> dereferences to.
> I believe the jabber folks were thinking about adding an entry for JID.
email+webfinger seems to be gaining some traction, tho im not sure if that's
yet able to store a public key, and you may not wish to disclose your email

> thoughts? controversial opinions?
> Steph.
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