Re: [VoT] VoT Identity Proofing and individual claims

Justin Richer <jricher@mit.edu> Wed, 13 September 2017 17:57 UTC

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From: Justin Richer <jricher@mit.edu>
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Date: Wed, 13 Sep 2017 13:57:48 -0400
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To: Phil Hunt <phil.hunt@oracle.com>
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Subject: Re: [VoT] VoT Identity Proofing and individual claims
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It applies to the IdP’s judgement across the entire assertion. How that’s calculated when the trust in different attributes differs will vary depending on the IdP, and probably defined by rules within the trust framework that defines the vector values themselves. NIST 800-63-3 volume A, for example, is very clear about how to handle all the attributes collected at different levels. If you were using NIST’s encoding of VoT, specified in the upcoming volume D of that document, then you’d be bound by those rules as an IdP. A university group, like you’re talking about below, might have different rules under its own trust framework and vector component definitions.

It looks like you might be asking if this is about per-attribute metadata. If you read the introduction, we explicitly state that we’re not trying to solve per-attribute metadata. If you’d like that kind of data, you’re looking for a different kind of solution, of which there have been numerous attempts over the years. Generally speaking, attribute metadata systems look great on paper but are incredibly complicated for RP’s to implement. When we wrote VoT, we directly decided to take a different approach, something between the granularity of attributes and the single-scale of LOA. 

This level of granularity is very, very useful in the real world, otherwise we wouldn’t have dozens of international trust frameworks based around the concept of proofing an individual and tying that account to a set of proofed attributes. There isn’t an easy way to express something complex as “We’re sure this is Justin but aren’t sure about his medical degree” in any VoT implementation that I’ve seen to date, and especially not in the example values given in the spec itself. But if you really wanted to, you could have something like:

 - P3: High level of confidence in individual’s name, address, phone, eye color, and shoe size
 - Pm: In person verification of a medical degree by making the claimant perform surgery on the verifier.

So if you wanted to express that, you could say “P3.Pm” or just “P3” if you weren’t so sure about that medical degree. However, like I described above, I don’t think this is a good solution for that as you’d need to get really specific with each attribute. If you really need that level of expressiveness, you’ll want a different solution and VoT doesn’t work for you. However, just because it doesn’t solve this use case doesn’t mean it’s not useful in many others. VoT is a tool fit for a purpose that we tried to express in the intro text, it fits in between attribute metadata and single scalar measurements. And in fact, you could use it side by side in the same system, and I see no conflict in this.

Don’t deny the world a hammer just because you think you need a screwdriver.

 — Justin

> On Sep 13, 2017, at 1:01 PM, Phil Hunt <phil.hunt@oracle.com>; wrote:
> 
> Section 3.1
> 
> Does 3.1 apply to the identifier issued, to the whole assertion? 
> 
> An Identity is usually an identifier and a set of claims.
> 
> So what about claims?   Some claims may be issued by a provider (and thus are P3) while others may be provided as self asserted by the subject.  Some, as in banking may have involved a physical documents or other mechanism and thus all claims are not equal.
> 
> I have trouble determining the affect of P0-P3 and worry that privilege escalation will occur since not all claims are equal.  There isn’t really a way to say “We’re confident this is Justin, we’re just not so sure about his medical degree”.
> 
> Consider a university knows student numbers and degrees and courses completed. Is it authoritative over nationality, residence, addresses?  Maybe. Maybe not.
> 
> Consider a social network. In many cases they can be considered authoritative over the social network identity (P3) but know nothing about most users.
> 
> I’m just not sure identity proofing as expressed is actually useful.
> 
> Phil
> 
> Oracle Corporation, Identity Cloud Services Architect
> @independentid
> www.independentid.com <http://www.independentid.com/>phil.hunt@oracle.com <mailto:phil.hunt@oracle.com>
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