Re: JSON-LD vs JWT for VC

Hi Kim,

Oliver and I had lunch yesterday and basically discussed the process of
doing work in the VCWG.  Oliver joined yesterday's VCWG call and offered to
send in an initial PR of a rough draft of some spec additions to support
JWT-based VCs, just to get the conversation going.  We have a tight
schedule, but speaking with my VCWG chair hat on, I see no reason why the
WG can't arrange for some additional call time focused on this topic if
that will help it move along.

Thank you for the offer of airtime in the CCG.  If the work is ready to be
standardized it should happen in the VCWG.  If it turns out that it's not
ready the chairs of the CCG and VCWG can discuss options for how best to
progress the work.

-- dan

On Tue, Oct 30, 2018 at 4:51 PM Kim Hamilton Duffy <kim@learningmachine.com>
wrote:

> Thank you Dan and Oliver for doing this. I’m very encouraged by this
> iteration of JSON-LD/JWT email threads, and eagerly awaiting your results.
>
> I imagine the scope could be a bit beyond what you can take on for VCWG,
> so let us know if you’d like CCG airtime/involvement. We’ve already
> discussed taking on some tooling improvements (mentioned above), but that’s
> just part of the solution.
>
> On Tue, Oct 30, 2018 at 2:28 AM Daniel Burnett <
> daniel.burnett@consensys.net> wrote:
>
>> It turns out that Oliver and I are both in Prague this week, so we will
>> meet first in person to brainstorm practical options for how this work
>> might occur in relation to the VCWG's current specifications and timelines.
>>
>> -- dan
>>
>> On Tue, Oct 30, 2018 at 4:54 AM Oliver Terbu <oliver.terbu@consensys.net>
>> wrote:
>>
>>> Hi Dan,
>>>
>>> I have been following this thread for a while now. After last RWOT and
>>> especially after last IIW, I can clearly see that we should make progress
>>> in both directions: JWT and JSON-LD. As Pelle mentioned, it doesn’t make
>>> sense to refer to articles listing the pros and cons of one option over the
>>> other. We already are aware of those. It is time to make progress.
>>>
>>> @Dan: I am very interested and I am willing to contribute on a proposal
>>> for a JWT-based VC specification as suggested by Dan Burnett. Does it make
>>> sense to organise separate calls which are only JWT-specific until we have
>>> a first draft and then bring it to the W3C CC (VC) group? In this case, I
>>> am happy to arrange these calls for all people that are interested.
>>>
>>> If you believe separate calls do not make sense, please let me know what
>>> would be an appropriate approach.
>>>
>>> Thanks,
>>> Oliver
>>>
>>> On 29. Oct 2018, at 21:20, Daniel Burnett <daniel.burnett@consensys.net>
>>> wrote:
>>>
>>>
>>>
>>> On Sun, Oct 28, 2018 at 5:32 PM Pelle Braendgaard <
>>> pelle.braendgaard@consensys.net> wrote:
>>>
>>>> Just to clarify. I’m not a fan of canonicalization for the reasons
>>>> mentioned here, but it could work with proper tooling.
>>>>
>>>> My main problem is that it you have to be intimately  knowledgeable of
>>>> how json-ld,  canonicalization and even how did resolution works before you
>>>> can safely take a verifiable claim and verify it.
>>>>
>>>> It is even more complex due to the nested aspects of many parts of the
>>>> proposed VC standards.
>>>>
>>>> In many cases in its extreme flexibility it has the same very dangerous
>>>> aspects of xmlsig.
>>>>
>>>> For VC to actually be used it needs to have tooling that can safely be
>>>> used by regular bank or web devs to verify what is sent to them.
>>>>
>>>> Ideally it would be simple enough that we could get a plethora of
>>>> implementations as well, but it seems unlikely since it’s fans don’t seem
>>>> interested in fixing these aspects in the name of flexibility and
>>>> readability.
>>>>
>>>> This is why I propose a workable middleground. Those who believe
>>>> strongly in the power of JSONLD invest in useable tooling to make it
>>>> foolproof.
>>>>
>>>> At the same time those of us that are sceptical work to create better
>>>> proposals for VC based on JWT.
>>>>
>>>
>>> The Verifiable Claims Working Group, the standards-track group where
>>> this work is being finalized, takes this very seriously, having discussed
>>> this topic at every face-to-face meeting since inception and always
>>> reaching a conclusion of 'we would like more detailed proposals from those
>>> who prefer a JWT-based approach'. As a member of the VCWG yourself, you are
>>> no doubt aware that we have been seeking precisely such detailed proposals
>>> since the beginning of that group in March 2017.
>>>   As a co-chair of the VCWG, I would like to ask you to expedite that
>>> work.  Our group is chartered to complete in March of next year, with an
>>> expectation of feature / substantive content freeze on November 6th of this
>>> year (yes, in just a couple of weeks).  If your detailed proposals come in
>>> after that time we may need to consider adding them in a version 2.0
>>> when/if such additional work is chartered.  We look forward to receiving
>>> your (and others') proposals.
>>>
>>>
>>>> Currently the state of libraries for json ld signature validation means
>>>> that most of us working on real production apps will not support it.
>>>>
>>>> The problem is not solved by a back and forth sending links on the pros
>>>> and cons. I think we’re all aware of them and are past that.
>>>>
>>>> Thanks. Hopefully we can make progress.
>>>>
>>>> Pelle
>>>>
>>>> On Sun, Oct 28, 2018 at 17:04 Anders Rundgren <
>>>> anders.rundgren.net@gmail.com> wrote:
>>>>
>>>>> On 2018-10-28 19:37, Dean Kevin Poulsen wrote:
>>>>> > Anders,
>>>>> >
>>>>> > Maybe canonicalization can be eliminated, because the need for
>>>>> canonicalization stems from the core issue, which is:
>>>>> >   —  The requirement that signed content be modified after being
>>>>> signed.
>>>>>
>>>>> Kevin,
>>>>> It is rather the wish using standard JSON tools which (typically) do
>>>>> not respect property order that calls for canonicalization.
>>>>>
>>>>> In the case of JSON-LD it is even worse since the requirement is to
>>>>> verify that both sides use the same graph expansion scheme.
>>>>>
>>>>> I started with building unique JSON tools which preserved property
>>>>> order and textual representation of elements.  This worked flawlessly but I
>>>>> had to give it up anyway since nobody wanted to change their parser :-( The
>>>>> recent draft has a potentially very interesting quality: It can (with ease)
>>>>> be implemented as a option in a JSON serializer.  Sorting is a one-liner
>>>>> and number serializing is well defined and open sourced.  I use the
>>>>> canonicalization scheme for multiple purposes in my applications.  Example:
>>>>> https://cyberphone.github.io/doc/saturn/bank2bank-payment.html#userauthz
>>>>> (requestHash).
>>>>>
>>>>> Enveloping and detached signature schemes do not require explicit
>>>>> modification of signed data but I stick to enveloped signatures because
>>>>> they preserve the structure of the data.
>>>>>
>>>>> Related discussion in the IETF:
>>>>> https://www.ietf.org/mail-archive/web/jose/current/msg05752.html
>>>>>
>>>>> Regards,
>>>>> Anders
>>>>>
>>>>>
>>>>> Then, the receiver is required to recreate the signed content through
>>>>> prescribed manipulations.
>>>>> >
>>>>> > “Seasoned XML developers recalling difficulties getting signatures to
>>>>> >     validate (usually due to different interpretations of the quite
>>>>> >     intricate XML canonicalization rules as well as of the equally
>>>>> >     extensive Web Services security standards)…”
>>>>> > — From the introduction to:
>>>>> https://tools.ietf.org/html/draft-rundgren-json-canonicalization-scheme-01
>>>>> >
>>>>> >
>>>>> > ------
>>>>> > My opinion:  SIGNED CONTENT SHOULD NOT BE MODIFIED AFTER IT IS
>>>>> SIGNED.
>>>>> >
>>>>> > To simplify the proposal, here's a signed JSON-LD in the existing
>>>>> standard and the same signed JSON-LD revised per my proposal:
>>>>> >
>>>>> >
>>>>> > My proposal does two things:
>>>>> >
>>>>> > 1.  It splits the “proof” array into two arrays:  “proofMetadata”
>>>>> and “proofValue”.
>>>>> > 2.  It puts the signed content into a “signedContent” array.  The
>>>>> “proofValue” immediately follows the “signedContent”
>>>>> >
>>>>> > This pulls the “proofValue” out of the signed content, eliminating
>>>>> the need to modify the signed content after it has been signed (except in
>>>>> the case of signature sets, where minimal modification is suggested for
>>>>> convenience).
>>>>> >
>>>>> >
>>>>> > —
>>>>> > You mentioned that one form of canonicalization doesn’t require the
>>>>> signature to be included.  I can’t find that option in the links that you
>>>>> sent.  Can you point me in the right direction?
>>>>> >
>>>>> > Thanks,
>>>>> > Kevin
>>>>> > [“Dean” is a title, not my name.  :) ]
>>>>> >
>>>>> >
>>>>> >
>>>>> >
>>>>> >> On Oct 27, 2018, at 11:27 PM, Anders Rundgren <
>>>>> anders.rundgren.net@gmail.com <mailto:anders.rundgren.net@gmail.com>>
>>>>> wrote:
>>>>> >>
>>>>> >> Hi Dean,
>>>>> >>
>>>>> >> I don't completely follow your proposal.  Does it actually remove
>>>>> the need for RDF/LD canonicalization?
>>>>> >>
>>>>> >> Anyway, there are subtle differences between formats and one is if
>>>>> the signature parameters should be included or not.  Including them
>>>>> requires that the data is modified by the signature and verify process.
>>>>> >>
>>>>> >> FWIW, this is how my Java verifier code deals with this particular
>>>>> topic for JSON Clear text Signatures:
>>>>> >>
>>>>> >>    // 1. Make a shallow copy of the signature object
>>>>> >>    LinkedHashMap<String, JSONValue> savedProperties =
>>>>> >>        new LinkedHashMap<String,
>>>>> JSONValue>(innerSignatureObject.root.properties);
>>>>> >>    // 2. Hide the signature value property for the serializer...
>>>>> >>
>>>>>    innerSignatureObject.root.properties.remove(JSONCryptoHelper.VALUE_JSON);
>>>>> >>    // 3. Serialize ("JSON.stringify()")
>>>>> >>    normalizedData =
>>>>> signedData.serializeToBytes(JSONOutputFormats.CANONICALIZED);
>>>>> >>    // 4. Restore the signature object
>>>>> >>    innerSignatureObject.root.properties = savedProperties;
>>>>> >>
>>>>> >> Regards,
>>>>> >> Anders
>>>>> >
>>>>>
>>>>> --
>>>> *Pelle Brændgaard // uPort Engineering Lead*
>>>> pelle.braendgaard@consensys.net
>>>> 49 Bogart St, Suite 22, Brooklyn NY 11206
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>>>>
>>>
>>> --
> Kim Hamilton Duffy
> CTO & Principal Architect Learning Machine
> Co-chair W3C Credentials Community Group
>
> kim@learningmachine.com
>