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Re: Surveying names for trust states above and below a single VC or DID.

From: David Chadwick <D.W.Chadwick@kent.ac.uk>
Date: Tue, 15 Sep 2020 08:49:49 +0100
To: public-credentials@w3.org
Message-ID: <1441c938-e6cb-54b3-0091-75ca58c62020@kent.ac.uk>
Hi Orie

Please let me correct you

On 15/09/2020 01:48, Orie Steele wrote:
> I've already said a good deal on the github thread, but I will restate 
> my perspective here, maybe it will come across cleaner.
>
> There are 2 concepts we are trying to standardize / improve the 
> standardization of....
>
> 1. Establishing an Identity ( DID / id_token )

Establishing an Identifier, not an identity

kind regards

David

> 2. Establishing attributes or capabilities of an Identity. ( VC / 
> Z-Caps / access_token )
>
> In the OIDC world, we rely on a trusted issuer to provide id_token and 
> access_token to entities, and holding them grants access to systems.
>
> When we use OIDC we are trusting:
>
> 1. The OpenID Provider (OP)... Google / Okta / Microsoft ... These 
> guys have private keys they use to sign the tokens... if they are 
> compromised, we are impersonated...
>
> https://news.ycombinator.com/item?id=23362149 
> <https://news.ycombinator.com/item?id=23362149>
>
> "I found I could request JWTs for any Email ID from Apple and when the 
> signature of these tokens was verified using Apple’s public key, they 
> showed as valid. This means an attacker could forge a JWT by linking 
> any Email ID to it and gaining access to the victim’s account."
>
> 2. We are trusting OIDC as well, in a way this is like trusting a DID 
> Method... we are trusting a standardized way of establishing 
> identity... in the case above... that's what happens when you don't 
> implement the standard correctly.... I am not trying to hate on Apple 
> or OIDF... there are standards and there are implementations... we 
> need to be able to trust both.
>
> 3. We are trusting the relying party (RP), here are some of the things 
> we are trusting the RP to do... 
> https://infosec.mozilla.org/guidelines/iam/openid_connect.html#session-handling 
>
>
> When using DIDs and VCs we are making some similar trust assumptions.
>
> 1. Instead of trusting the OP, we are trusting the DID Controller to 
> have good opsec.
> 2. Instead of trusting OIDC and TLS, we are trusting the DID Method 
> and any ledger / crypto associated with it.
> 3. We still trust Relying or Requesting parties to handle our data 
> correctly.
>
> Regarding material on either side of the VC / id_token...
>
> There is material collected by an issuer that is used to cross check 
> credential data / support authentication....
>
> There is material collected by a verifier that is used to cross check 
> the credential data / support authentication...
>
> When someone gets a passport issued, they may be required to present 
> multiple documents, papers... This DIF spec defines a format for 
> making a presentation of material... 
> https://identity.foundation/presentation-exchange/ ... this might be 
> the first step in obtaining a credential... in other words... 
> authenticating and providing / presenting documents and credentials is 
> a thing that comes before receiving a credential.
>
> I'm not actually sure how the no fly list works, but I assume it's a 
> list that is checked regardless of if the traveler has a valid drivers 
> license... so this is information a verifier uses to decide if the 
> credentials provided  are sufficient for a holder to proceed..... 
> Another example is tainted bitcoins, which may have at one time been 
> held by a dark market.... when the DOJ auctions them off, they sell 
> for less, in part because every time you use them, you will trigger 
> the flags associated with suspicious activity (if the vendor uses 
> Chainalysis or similar...).. you can read more about this topic here: 
> https://www.bitcoininsider.org/article/81896/theres-no-such-thing-tainted-bitcoins
>
> The bitcoin will transfer (if the signature is valid). The digital 
> passport will verify (if the proof is valid)... but what the verifier 
> does in the way of additional processing beyond that, is up to them... 
> There are a lot of cases where asking for additional checks makes a 
> lot of sense.... like when you are first interacting with a party, or 
> if you have not seen them in a long time...
>
> I personally don't like the words "Verifiable Credential" :) mostly 
> because "verify" is used to describe all these scenarios in at least 3 
> representations:
>
> 1. The data is in the expected format ( validation )
> 2. The data contains all the required fields ( validation )
> 3. The data contains no unexpected fields ( sanitization / validation )
> 4. The data contains a signature, and a key identifier (the data was 
> signed)
> 5. The signature is verifiable (the key identifier can be 
> dereferenced to public key bytes)
> 6. The signature is verified (the data was signed by the key produced 
> by 5)
> 7. The signing key is "active" / "not revoked" (the key is "current" / 
> not in a key revocation list of a PGP server)
> 8. The data issuance date is in the past (the credential is not 
> forward dated)
> 9. The data expiration date is not passed (the credential has not expired)
> 10. The credential subject is not in some deny-list (untrusted 
> subject.... like suspected terrorist)
> 11. The credential issuer is not in some deny-list ( untrusted 
> issuer.... like a suspected compromised issuer... like apple before 
> they patched the 0 day above ; )
>
> The VC Spec really focused on 1-9... It correctly left 10 and 11 to 
> the verifiers to decide... however not all VC representations chose to 
> define 1-9 fully... so what "verify" means... turned out to not really 
> be as helpful as we might have hoped....especially when applied to the 
> general concept of a "VC" as opposed to "Ed25519Signature2018 Linked 
> Data Proof" or "EdSA VC JWT", or a Hyper Ledger Indy CL Signature 
> Proof....
>
> The VC Data Model didn't have OIDC to define key lookups... and it 
> didn't have a single representation, so data sanitization is handled 
> differently for each representation (or not handled)... it didn't rely 
> on a single cipher suite, like IANA JOSE... so all the crypto is 
> represented differently.... and because it didn't have the did spec or 
> OIDC.... the concept of "revoked" was really tough to define... 
> because there were no DID Documents or well known JWKs.... there were 
> no key servers (PGP was strangely not supported formally)....
>
> These issues, coupled with 2 semi well defined representations (JWT 
> and JSON-LD) and a pseudo defined ZKP / LD representation... make it 
> very hard to understand what "verify a vc" actually means.
>
> But IMO this is what it means:
>
> 1. The VC matches the format described in the VC Spec
> 2. The VC has a proof.
> 3. The VC Proof can be checked now, and maybe for points in the past 
> as well. ( depends on your VC and on your issuer / subject identifier 
> choices ).
> 4. The VC has date material for issuance and expiration, and even if 
> the signature is valid, if the dates are wrong the VC does not verify.
>
> I prefer to separate the concept of data model conformance and 
> cryptographic checks from business logic / credential processing logic...
>
> This is probably a good time for me to stop rambling and say.... 
> despite all its issues, the VC Spec accomplished a lot and the DID 
> Spec will cover many of the obvious gaps in the VC spec, 
> particularly around the revocation of keys and thereby the revocation 
> of credentials.
>
> OS
>
>
>
> On Mon, Sep 14, 2020 at 4:25 PM Christopher Allen 
> <ChristopherA@lifewithalacrity.com 
> <mailto:ChristopherA@lifewithalacrity.com>> wrote:
>
>     On Mon, Sep 14, 2020 at 12:56 PM Orie Steele wrote on a github
>     DID-WG issue "Re: [w3c/did-core] need to clarify revocation vs.
>     rotation (#386)
>     <https://github.com/w3c/did-core/issues/386#issuecomment-692279254>":
>
>          1. "verification" is not just does the signatures match....
>             its what is the trust context for this... how old is this,
>             how good is the opsec of the issuer, etc....
>
>     This raises a problem for me which is that we don't have good
>     language for DIDs and VCs in their intermediate states, above and
>     below, and in particular between conforming to the data model and
>     "verifiable" and then continuing onward toward satisfying a
>     complex trust context.
>
>     * Clearly one desirable state is "Verifiable" — but doesn't that
>     mean it is not verified yet? Clearly in VCs that is true if
>     nothing more than that the spec has no required trust model. So
>     lets set that as the middle —"Verifiable" is some level of
>     conformity where you have sufficient data and proofs such that you
>     can say the VC (or DID) can be verified later.
>
>     * What are states below this level, including both error states
>     (invalid, revoked, missing information), but also intermediate
>     states which include that the data is valid but you don't
>     understand the proof (or one of the proofs)?  Or things like
>     understanding or not understanding all the context, but you have
>     enough to know you have what you need? What are these
>     "pre-verifiable" states called?
>
>     * What are states above the "verifiable" level, including needed
>     other DIDs or VCs referred to that also need to be fetched before
>     the DID or VC can be fully passed to a trust model for final
>     approval? What is actually called when you've confirmed everything
>     (all the linked data outside of the DID VC) is verified, but
>     you've not checked things like out-of-band revocation? What is it
>     called when you've not passed it through a trust model? What is
>     the ultimate result called, when you've done all the work, and the
>     trust model at the end says "Ok"?
>
>     I'd really like to see some clarity here, as when I'm working with
>     others who don't have 5+ years of socializing on VC and DID issues
>     get very confused because our current major platforms use
>     different language for these states. And the insiders that do have
>     that socialization are making assumptions about similar words of
>     others that may not be correct.
>
>     For now, can we start with a survey? Please share what YOU call
>     these intermediate states above and below a "Verifiable Claim"
>     specifically, and also if they are different from the same states
>     above and below a DID?
>
>     In particular, I'd love Sam to say what they are for KERI, someone
>     from Sovrin, someone from DIF, and someone from Digital Bazarr.
>
>     Thanks!
>
>     — Christopher Allen
>
>
>
>
> -- 
> *ORIE STEELE*
> Chief Technical Officer
> www.transmute.industries
>
> <https://www.transmute.industries>
Received on Tuesday, 15 September 2020 07:50:08 UTC

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