Re: Cryptographically Enforceable Issuer Policies (forked

It's only bad in the sense that much of the SSI protocol work is predicated
on never "calling home" as a privacy and self-sovereignty feature. For
example, a common feature such as revocation would be trivial if the
Verifier could call home to check but instead we have some much more
complex schemes that involve things like dead-drops to do that job.

As a privacy advocate, I would say the data subjects should have maximum
control over their credentials and the Issuer should have as little control
as possible. If the subject decides it's ok to have the verifier call home,
then the subject can run an authorization or presentation server and avoid
creating unnecessary copies and running a personal data store. In other
cases, when the subject really mistrusts the Issuer, they would insist on
having a copy of the credential and using only protocols that do not "call
home". The choice to trust the Issuer should be the Subject's alone and
Issuer protocols should be agnostic to the Subject's choice.

Here's some detail about this:
https://github.com/w3c-ccg/vc-http-api/issues/186

- Adrian

On Fri, May 21, 2021 at 8:45 PM <steve.e.magennis@gmail.com> wrote:

> r.e. they might as well be calling home to the Issuer.
>
>
>
> That sounds bad. Is it bad or am I not understanding how these
> interactions should work
>
>
>
> *From:* Adrian Gropper <agropper@healthurl.com>
> *Sent:* Friday, May 21, 2021 5:39 PM
> *To:* Steve Magennis <steve.e.magennis@gmail.com>
> *Cc:* Joosten, H.J.M. (Rieks) <rieks.joosten@tno.nl>; public-credentials <
> public-credentials@w3.org>; Naveenaa <n.a.karthikeyan@student.utwente.nl>
> *Subject:* Re: Cryptographically Enforceable Issuer Policies (forked
>
>
>
> In most cases, the Issuer and Key Smitty are controlled by the same
> entity. That's evidenced by the transfer of policies in 1. When the
> Verifier contacts Key Smitty in 9., they might as well be calling home to
> the Issuer.
>
>
>
> - Adrian
>
>
>
> On Fri, May 21, 2021 at 8:25 PM <steve.e.magennis@gmail.com> wrote:
>
> At a high level, does this mol represent the primary envisioned
> interactions between Issuer, Keysmith, Holder and Verifier?
>
>
>
>
>
> 1: Issuer submits a policy to the KeySmith
>
> 2: KeySmith records the policy and
>
> 3: Gens key pair(s) according to CP-APB
>
> 4: Issuer stores key
>
> 5: Issuer encrypts credential with key
>
> 6: Issuer delivers encrypted credential to Holder
>
> 7: Verifier wants to verify credential (presentation definition)
>
> 8: Holder delivers encrypted credential to Verifier (presentation
> submission)
>
> 9: Holder requests decryption key from KeySmith
>
> 10: KeySmith sends a presentation definition to Verifier based on the
> policy that needs to be satisfied. Verifier temporarily shifts role to
> being a Holder
>
> 11: Verifier (as holder) submits credential to KeySmith in the hope of
> being able to satisfy the requisite policy conditions
>
> 12: KeySmith confirms the policy conditions are met and provides the
> Verifier with the decryption key
>
> 13: Verifier decrypts the credential and proceeds with any additional
> verification or processing
>
>
>
> *From:* Joosten, H.J.M. (Rieks) <rieks.joosten@tno.nl>
> *Sent:* Thursday, May 20, 2021 10:15 PM
> *To:* steve.e.magennis@gmail.com
> *Cc:* 'public-credentials' <public-credentials@w3.org>; Naveenaa <
> n.a.karthikeyan@student.utwente.nl>
> *Subject:* RE: Cryptographically Enforceable Issuer Policies (forked
>
>
>
> Hi Steve,
>
>
>
> Before answering your question, let me tell you this is still stuff we are
> coming to grips with – it is the subject of a masters thesis that Naveena
> Anaigoundanpudur Karthikeyan is working on with TNO. So what I write below
> are ideas that I still need to see verified.
>
>
>
> We introduce a new role, which we call `KeySmith`, that generates all keys
> involved. Specifically:
>
>    - It publishes the public key (and some other stuff) that issuers can
>    use to encrypt credentials under their policy, and
>    - It provides a Decryption-Key Provisioning Service (DKPS) that other
>    parties can supply attributes to and then obtain a decryption key that
>    enables them to decrypt any credential that was encrypted under a policy
>    that is satisfied by the attributes that the party supplied.
>
>
>
> Determining whether or not a verifier (or a holder for that matter) can
> decrypt a credential relies on:
>
>    - The crypto-magic that is called Ciphertext Policy Attribute Based
>    Encryption (CP-ABE);
>    - The rigor with which the KeySmith validates the attributes that
>    parties supply as they request a decryption key.
>
>
>
> Consequently, parties that issue credentials under such a policy must (be
> able to) determine
>
>    - That he attributes that a KeySmith uses to generate decryption keys
>    are sufficient for expressing its policy
>    - That the process that the KeySmith uses to validate the attributes
>    that parties provide as they request a decryption key, provides sufficient
>    assurance that the (cryptograhpic) evaluation of the policy is also valid.
>    And I think this is the trickiest part.
>
>
>
> Rieks
>
>
>
> *From:* steve.e.magennis@gmail.com <steve.e.magennis@gmail.com>
> *Sent:* donderdag 20 mei 2021 16:17
> *To:* Joosten, H.J.M. (Rieks) <rieks.joosten@tno.nl>; 'Luca Boldrin' <
> luca.boldrin@infocert.it>; 'Michael Herman (Trusted Digital Web)' <
> mwherman@parallelspace.net>
> *Cc:* 'public-credentials' <public-credentials@w3.org>; Kruijssen, A.
> (Age) <age.kruijssen@tno.nl>; Stornebrink, M.H.M. (Michiel) <
> michiel.stornebrink@tno.nl>
> *Subject:* RE: One subject, 2 VCs, 2 duplicate properties
>
>
>
> … forking the conversation r.e. Cryptographically Enforceable Issuer
> Policies
>
> @Joosten, H.J.M. (Rieks) <rieks.joosten@tno.nl>, how would it be
> determined if a Verifier satisfies policy conditions? Really interesting
> idea.
>
>
>
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