Re: ERC-721 Non-Fungible Token Standard on Ethereum vs. VCs on Hyperledger Indy

Last year we published this paper in NDSS DISS workshop

https://arxiv.org/pdf/2001.10461.pdf

We used OAuth2.0 to produce ERC-721 tokens which then were used as access tokens. So related to this discussion may be it will be more relevant to consider ERC-721 for storing zcap tokens (https://w3c-ccg.github.io/zcap-ld/). ZCAPs support delegation by design (https://w3c-ccg.github.io/zcap-ld/#delegation).

Best,
Nikos
--
Nikos Fotiou - http://pages.cs.aueb.gr/~fotiou
Researcher - Mobile Multimedia Laboratory
Athens University of Economics and Business
https://mm.aueb.gr

> On 12 Feb 2021, at 2:53 PM, Michael Herman (Trusted Digital Web) <mwherman@parallelspace.net> wrote:
> 
> Thank you Carlos and Will,
>  
> The user scenario is one of those classic “art on the blockchain” kinds of scenarios …so transferability is important.
>  
> I believe the ability to revoke a VC for the old owner of a piece of artwork and to re-issue a new VC for the new owner of the artwork should be sufficient for this scenario.  Thoughts?
>  
> The existence of existing ECR-721 market places is an important Ethereum advantage: e.g. https://opensea.io/
>  
> Thank you both,
> Michael
>  
>  
> From: Carlos Bruguera <cbruguera@gmail.com> 
> Sent: February 12, 2021 4:10 AM
> To: Will Abramson <wip.abramson@gmail.com>
> Cc: Michael Herman (Trusted Digital Web) <mwherman@parallelspace.net>; Credentials Community Group <public-credentials@w3.org>
> Subject: Re: ERC-721 Non-Fungible Token Standard on Ethereum vs. VCs on Hyperledger Indy
>  
> Just a quick comment, ERC-721 defines an interface the token contracts should implement to comply with it, but it doesn't enforce any particular behavior, therefore it's possible to write a non-transferable ERC-721, still complying with the interface as long as the `transfer` function is provided, it would either revert or not do anything.
>  
> On Fri, Feb 12, 2021 at 5:51 PM Will Abramson <wip.abramson@gmail.com> wrote:
> An immediate difference is that ERC-721 or I believe any token on Ethereum is transferable. I can send it to you, you could sell it to someone else using a platform like OpenSea, etc.
>  
> This is not obviously possible using the Indy stack today without some hack involving the issuer of the credential revoking and re-issuing it. I believe there is some work in Ursa around the crypto for transferrable credentials but not sure what status and priority this has.
>  
> Also, the ERC-721 keeps track of tokens and token holder addresses available to anyone who queries the contract.
>  
> They are a couple that come to mind,
>  
> Will
>  
> On Thu, Feb 11, 2021 at 11:05 PM Michael Herman (Trusted Digital Web) <mwherman@parallelspace.net> wrote:
> I hope this isn’t stretching the favorable use of the CCG mailing list…
>  
> When are Hyperledger Indy/Sovrin VCs better than Ethereum smart contracts for NFEs/NFTs (non-fungible entities/tokens)?
>  
> It seems obvious but I don't have a detailed/worked out answer.  One project I'm associated with wants to use the ERC-721 Non-Fungible Token Standard on Ethereum but I believe VCs are a better route to take. Part of the desire to stay on Ethereum is there is quite a vibrant NFT community on Ethereum and lots of different EC-721 tokens. 
>  
> https://eips.ethereum.org/EIPS/eip-721
>  
> What are the considerations/decision points/knock-offs?
>  
> Best regards,
> Michael Herman
> Sovrin Foundation Self-Sovereignist
>  
> Self-Sovereign Blockchain Architect
> Trusted Digital Web
> Hyperonomy Digital Identity Lab
> Parallelspace Corporation
>  
> <image001.jpg>