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oauth-wg / oauth-selective-disclosure-jwt

https://datatracker.ietf.org/doc/draft-ietf-oauth-selective-disclosure-jwt/
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A new section about "End-User intrackability" should be added #516

Closed Denisthemalice closed 2 weeks ago

Denisthemalice commented 3 weeks ago

This text addition proposal results from the split of section 10.1:

10.2. End-User intrackability

Intrackability is a property whereby one or more Issuers are prevented to learn by which Verifier(s) a SD-JWT that they have issued has been consumed (or will be consumed).

The following types of intrackability are considered here:

  • End-User intrackability by one Issuer: incapability of an Issuer alone to learn to which Verifiers a SD-JWT that it has issued will be presented by a Holder.

  • End-User intrackability by both Issuers and Verifiers: incapability of one Issuer, with the help of one Verifier, to learn by which Verifier a SD-JWT that it has issued has been consumed.

    End-User intrackability by one Issuer is natively supported when using SD-JWTs since a SD-JWT does not contain an "aud" claim.

    End-User intrackability by both Issuers and Verifiers cannot be supported using SD-JWTs, as soon as a Verifier communicates the SD-JWT either to an authority upon its request that will then communicate it to the Issuer or deliberately communicates the SD-JWT to the Issuer.

    However, some mechanisms using zero-knowledge proofs (ZKP) may be able to support this property.

    Ii is important to notice, for example, that a national authority can require to get an access to the audit logs from both a Verifier and an Issuer to know whether a same SD-JWT has been logged in both files.

    Since the Issuer "needs to know its customer" (KYC), national authorities may be able to identify an End-User who made an access to a Verifier.

    Section 10.X (Storage of User Data) RECOMMENDS that after verification, Verifiers SHOULD NOT store the SD-JWT. Depending upon the context of use, this recommendation should or should not be followed since there exist cases where such property will be non- desirable in particular to fight against crime or money laundering.

paulbastian commented 3 weeks ago

The term unlinkability is established in literature and standards for this.