Re: On JSON-LD with DIDs and VCs

That's an excellent question. I've been ignoring it because Sovrin-style
presentations use JSON-LD only very modestly thus far--whereas we have
every intention of using JSON-LD's extensibility heavily on the credential
side. Perhaps I will catch up to your thinking eventually...

On Tue, Jan 7, 2020 at 3:26 PM Oliver Terbu <oliver.terbu@consensys.net>
wrote:

> My apologies for conflating VC and VP in my previous email. While I agree
> that this separation exists, I don't see that this can mitigate the
> described issue in all cases as the VP can still include the VC and the
> potentially malicious context.
>
> In that case, enforcing the validity checks at the verifier would cause
> verifiers to fail if the issuer had malicious intent. If there is enough
> pressure or incentive on verifiers to support these VCs, the system would
> need a fallback to support plain JSON to preserve the user's privacy. Then,
> the question is why should that not be the default case as it is also much
> simpler?
>
> Oliver
>
> On Tue, Jan 7, 2020 at 10:21 PM Daniel Hardman <daniel.hardman@evernym.com>
> wrote:
>
>> I think one of the reasons why the community has agreed to think of a
>> presentation and a credential as two different (though highly related)
>> types of data is that making the distinction allows us to make different
>> extensibility vs. security/privacy tradeoffs in credentials versus
>> presentations, per circumstances. Extensibility of *credentials* need
>> not trigger sacrifices in security/privacy of *presentations*, if we
>> don't conflate the two. But as long as we conflate the two, we create
>> unnecessary baggage in either direction.
>>
>> On Tue, Jan 7, 2020 at 2:01 PM Oliver Terbu <oliver.terbu@consensys.net>
>> wrote:
>>
>>> See my comments below ...
>>>
>>> On Tue, Jan 7, 2020 at 8:08 PM Manu Sporny <msporny@digitalbazaar.com>
>>> wrote:
>>>
>>>> On 1/7/20 1:22 PM, Oliver Terbu wrote:
>>>> > Note, that JSON-only processors won't have that issue and you can
>>>> > replace "government" with any type of issuers that have an interest
>>>> > in the online behavior of the user.
>>>>
>>>> JSON-only processors that don't have an extensibility mechanism will
>>>> fail to enable diverse industries to create their own credential types
>>>> and will fail in the market. What am I missing?
>>>>
>>>
>>> That is not related to the issue. However, I don't see that necessarily
>>> to happen without having JSON-LD but I recognized that this is a discussion
>>> where we will likely not come to a shared conclusion (see the most recent
>>> W3C DID WG discussion).
>>>
>>>
>>>>
>>>> This isn't purely a JSON vs. JSON-LD issue -- it's a more specific
>>>> version of the phone home problem and there are mechanisms (as Orie
>>>> deftly outlined in the previous email) that can prevent phone home if a
>>>> URL is going to be used to retrieve external information as a part of
>>>> the verification process. Note that the spec talks about this very
>>>> attack:
>>>>
>>>> https://www.w3.org/TR/vc-data-model/#validity-checks
>>>>
>>>> There are also multiple solutions to this specific concern (among the
>>>> ones that Orie has already mentioned), but the easiest ones at a higher
>>>> level are:
>>>>
>>>> * Wallets should mark VCs as potentially being used to track them if the
>>>>   JSON-LD Contexts are not well known.
>>>>
>>>> * Verifiers should reject VCs containing contexts that are not well
>>>>   known and/or loaded from a cache.
>>>>
>>>
>>> Companies that are large enough could exert enough pressure to dilute
>>> these checks. Furthermore, many of these checks are prone to errors as the
>>> complexity is quite considerable.
>>>
>>>
>>>>
>>>> ... and in the very worst case:
>>>>
>>>> * Industry launches a mix-net caching proxy for JSON-LD contexts if this
>>>>   really becomes an issue.
>>>>
>>>>
>>> I guess that could work :)
>>>
>>>
>>>
>>>> Does that answer your question, Oliver?
>>>>
>>>
>>> Partially, yes.
>>>
>>> Note, that does not mean that we won't support processing of JSON-LD in
>>> VCs.
>>>
>>> Still, I don't see any good reason why we should prioritise
>>> extensibility over security and privacy at theses layers.
>>>
>>> Oliver
>>>
>>>
>>>>
>>>> -- manu
>>>>
>>>> --
>>>> Manu Sporny (skype: msporny, twitter: manusporny)
>>>> Founder/CEO - Digital Bazaar, Inc.
>>>> blog: Veres One Decentralized Identifier Blockchain Launches
>>>> https://tinyurl.com/veres-one-launches
>>>>
>>>>