W3C home > Mailing lists > Public > public-credentials@w3.org > January 2017

Re: U-Prove

From: Dave Longley <dlongley@digitalbazaar.com>
Date: Tue, 3 Jan 2017 13:53:35 -0500
To: Phil Archer <phila@w3.org>, Credentials Community Group <public-credentials@w3.org>
Message-ID: <1fd1d0d7-e0d6-f4ae-1b00-aedd0f36e5c7@digitalbazaar.com>
On 12/30/2016 05:42 AM, Phil Archer wrote:
> Dear all,
>
> Can I ask this group for a view on U-Prove [1] please? In particular,
> the privacy aspects that appear to be superior to the architecture
> proposed for the VCWG. The issue boils down to trackability.
>
> Thanks

The quick answer is that the VCWG data model/syntax is
signature/tokenization scheme agnostic. We've looked at U-Prove and
don't yet see a reason why it can't be compatible with the data model
and syntax work we've proposed. U-Prove attribute values must be
transmitted (in addition to U-Prove tokens) when selectively disclosing
and verifying and the format recommended by the VCWG could be used here.

Also, there's nothing in the proposed architecture that prohibits the
use of similar unlinkability/untrackability characteristics as in
U-Prove. For example, the proposed data model does not require
long-lived or cross-domain identifiers. They may be randomly generated,
blind-signed, or even non-existent in some cases. The model also does
not prohibit the use of one-per-credential/token, blind-signed public
keys. There has been significant discussion of privacy considerations in
this group (some documented here [1]) and during Rebooting Web of Trust
Workshops that representatives from this group have attended.

Furthermore, the use cases covered by the VCWG include but extend beyond
simple pseudonymity scenarios such as proof-of-age. There are other
cases where stronger identity is required and where U-Prove's additional
(cryptographic and otherwise) complexity may not provide sufficient
benefit to justify its use. We're not presently taking a strong stance
on signature mechanisms used to secure verifiable claims. There is an
expectation, however, per the charter, that some mechanisms will be
recommended by the WG after careful consideration of the available
technologies and use cases.

In short, we believe that the VCWG work is not competitive with U-Prove
but complimentary.


1. https://opencreds.github.io/vc-data-model/#privacy-considerations

-- 
Dave Longley
CTO
Digital Bazaar, Inc.
http://digitalbazaar.com
Received on Tuesday, 3 January 2017 18:54:03 UTC

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