JSON-LD vs JWT for VC

On 29/10/2018 06:53, Anders Rundgren wrote:
> On 2018-10-28 22:30, Pelle Braendgaard 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.
> 
> Yes, the bigger question seems to be if VCs should be expressed in
> JSON-LD or in plain JSON.

The specification is meant to allow for VCs to be encoded in as plain
JSON as possible, with the minimum of LD features. However, at the
W3C TPAC meeting this week, it became very clear that there is a lot of
implicit knowledge about JSON-LD that is hidden in the current spec, and
that is required in order to fully understand the examples in the
specification. For example, there is a JSON-LD "@graph" feature that is
implicit in the current examples, and it was only this week that this
was explicitly stated to participants, causing surprise to some.

So allowing for plain JSON is still a work in progress.

regards

David
> 
> If you settle for JSON-LD you still have the option to only sign the
> actual JSON bytes using JWT although that may not be entirely "kosher".
> 
> Anders
> 
>>
>> 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.
>>
>> 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 <mailto: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>
>> <mailto: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 <mailto:pelle.braendgaard@consensys.net>
>> 49 Bogart St, Suite 22, Brooklyn NY 11206
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> 
> 
>

Received on Monday, 29 October 2018 14:51:52 UTC