This methods did:content has been registered with w3c did-methods.
https://w3c.github.io/did-spec-registries/#did-methods

Introduction

did:content is identifies content such as images, video, and music. The goal is to be able to comprehensively decentralized manage content and rights

Overview of did:content

Motivation

Recently, a wide variety of content uploaded on the Internet.　　
However, content identifiers depend on storage like a S3 / YouTube. As a result, if storage downs, access becomes difficult. Naturally, there are solutions such as Contents Delivery Network(CDN) like Cloudflare / Fastly, but it must be said that they are still managed in a centralized.
In this method, the goal is to support content resolution and improve availability by defining IDs that can resolve various types of storage, etc., centered on content.
In addition, we aim to increase the number of users by extending the authentication of rights holders to two types, anonymous and non-anonymous, by using cryptographic methods.

Status Of this document

This is a draft document

Syntax and Interpretation

# Content DID
did:content:<method-specific-id>

did-content:   "did:content:" + content-id
content-id:    Base58(RIPEMD160(sha3-256(DID Document without id)))

for examples:

did:content:3qrgME9eV7brjYsx3Ebbp9hubiQna1wcD1FdzuG4P1V6xmZwSdLXzCG

Its corresponding DID document is as follows:

{
  "@context": [
      "https://www.w3.org/ns/did/v1",
      "https://did.kataru.io/did/v1",
      "https://w3id.org/security/suites/secp256k1recovery-2020/v2"
  ],
  "id": "did:content:03Z5hdN7vxXyp5YW4WGqMYowMAB3SLG6tN2UjWb2DfAmkTHC1WYDfnjB",
  "controller": [
    "did:content:03Z5hdN7vxXyp5YW4WGqMYowMAB3SLG6tN2UjWb2DfAmkTHC1WYDfnjB#author",
    "did:content:03Z5hdN7vxXyp5YW4WGqMYowMAB3SLG6tN2UjWb2DfAmkTHC1WYDfnjB#rights-holder"
  ],
  "verificationMethod": [
     {
        "id": "did:key:3TL4YbgfwnJmJhyxKKDRpA81vB1QkWvvWRMioKQb6yv9HYwsZCpnVWB#controller",
        "type": "EcdsaSecp256k1RecoveryMethod2020", 
        "controller": "did:key:3TL4YbgfwnJmJhyxKKDRpA81vB1QkWvvWRMioKQb6yv9HYwsZCpnVWB"
     },
     {
        "id": "did:key:3qrgME9eV7brjYsx3Ebbp9hubiQna1wcD1FdzuG4P1V6xmZwSdLXzCG#delegate",
        "type": "EcdsaSecp256k1RecoveryMethod2020", 
        "controller": "did:key:3qrgME9eV7brjYsx3Ebbp9hubiQna1wcD1FdzuG4P1V6xmZwSdLXzCG"
     }
  ],
  "updation":["#controller", "#delegate"],
  "authentication": ["#controller", "#delegate"],
  "assertionMethod": ["#controller", "#delegate"],
  "royaltyRecipients": [
     {
        "recipient": "[email protected]",
        "ratio": 80
     }
  ],
  "service": [
    {
      "id": "#kataru",
      "type": "kataru",
      "serviceEndpoint": "https://kataru.io/content/mizuki"
    }
  ],
  "proof": {
    "type": "Secp256k1",
    "creator": "did:key:3qrgME9eV7brjYsx3Ebbp9hubiQna1wcD1FdzuG4P1V6xmZwSdLXzCG#key-1",
    "signatureValue": "0000fb29b515146a1633833c41c87fc902e3815394bf31d3d779172124fe653f100c07d99c1f485d34607765ec53c6c889b8c18dc477fa04e"
  }
}

Fragments

• #author if servive receive #author fragment, they should return authors of content
• #rights-holder if servive receive #rights-holder fragment, they should return rights-holder of content

Royalty Recipients

DID Resolver / Verifiable Data Registry　　

The DID Resolver creates a DID Document from arguments and generates a DID to be associated. 　　
In addition, it has a database that associates DIDs with DID Document storage locations. 　 　　

VerifiableDataRegistry

Currently, there are no specific provisions for where DID Documents should be stored.
but Verifiable Data Registry assumes use of common storage such as IPFS / S3.　　　
Therefore, we recommend that you choose a highly available storage location, such as an Instance or IPFS.

DID Resolver Functions

• GET /resolve?did=?
  1. Get location of did document from Database.
  2. Fetch the did document from Verifiable Data Registry.
  3. Return did document
• POST /create?contentType=&contentUrl=&signature= Store
  1. Generate a did document associated with arguments
  2. Generate new did
  3. Store a did document to Verifiable Data Registry like S3 / IPFS
  4. Insert a recode contains location and did.
  5. Return generated DID
• POST /update?did=&contentType=&contentUrl=&signature=
  1. Fetch the did document from Verifiable Data Registry.
  2. Update a did document
  3. Store new did document to Verifiable Data Registry like S3 / IPFS
  4. Update a recode
• POST /delete?did=
  1. Delete a recode

DID Operations

Create　(Register)

Creating DID and DID Document for Holders is done through the following steps:
　　　

The DID Document does not have a concrete property for content, and the DID and Content must be resolved on the External Service side.
The DID Document contains information about the controllers who can control the content and the users who can view it.
Note: key generate code

Resolve (Read)

Firstly, access the DID resolver, obtain a list of services in DID Document, access the external service that has the content, and obtain the contents.
The external service side checks the authorization based on the controller information in the DID document and executes the request.
(The Client may access the external service directly.)
The service determines authorization based on the DID Document.

Update (Replace)

　　

I expect updation is mainly used when
　　

• When updating a did document　　
• When changing the URL of Content　　　　
• When updating the Content delivery service 　 　　

Deactive (Delete)

　　　

Delete is only for deleting DID documents,　
If the VDR was S3, delete the Document in addition to the record.　　 If the VDR is IPFS, delete the record.　　 Deletion of the content itself is optional.
In other words, it only disables content resolution by DID.　
　　

Security and Privacy Considerations

Security

The following security considerations should be considered for the content DID method:
DID Resolver will check for authority with the signature of the Controller recorded in the correct DID document. It is cryptographically more secure than existing authenticate methods (like password).
In addition, the did:content DID Resolver is OSS and can be built by anyone, allowing service providers to manage server root privileges.

Privacy Considerations

The following privacy considerations should be considered for the content DID method:
In general, DID Docuement is for identifying an entity like content
DID content Resolver / DID document must not have Personally Identifiable Information (PII).

Update History

2023/07/28: release alpha version

Copyright

@MizukiSonoko