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Identifiers

Decentralized Identifier or DID is a critical component of verifiable data. A DID is a new type of unique identifier which can be created independent of a central authority. The subject that the DID refers to can prove control over the DID using cryptographic proofs. In a verifiable data context, a DID can be used to verify the provenance and ownership of the data by linking to the verification method for the attached proof.

Decentralized Identifier​

Different flavors of DIDs exist today. The flavor of a DID or more accurately the DID Method defines how C.R.U.D. operations for that DID type are executed. Each DID Method has different tradeoffs in specific use cases. For example, a did:web can be created without a Blockchain but DID Methods exist that have a dependency on a Blockchain. All of them are valid DIDs but have different guarantees.

The example below shows how a did:web for veramo.dev might look like.

did:web:veramo.dev

DID Creation​

When a DID is created, it is typically associated with a private and public key pair. The public key will be visible in the DID Document. This allows the controller/subject of the DID to generate proofs that are verifiable by anyone that has the corresponding DID Document for that DID. The process of retrieving the DID Document from a DID is called DID Resolution.

DID Resolution​

A DID Resolver can take DID as input and resolve the DID Document. This is an important concept in how data flows in verifiable data systems.

DID Document​

Every DID has a DID Document that describes the DID subject. In the case of did:web the DID Document is hosted on the website in the following format. It contains essential cryptographic information and also services that the DID has available. This is the foundation of how DIDs can start to communicate with each other.

// 20201110152830
// https://veramo.dev/.well-known/did.json

{
  "@context": "https://w3id.org/did/v1",
  "id": "did:web:veramo.dev",
  "publicKey": [
    {
      "id": "did:web:veramo.dev#0405aa19bb98a5fd29c15a730cb5064ca128dea19247b896b1a7bdad0b4bccccda9b47366cd1359e740d938e5a47d7bed0501150e8a1623805ac47c489421b1506",
      "type": "Secp256k1VerificationKey2018",
      "controller": "did:web:veramo.dev",
      "publicKeyHex": "0405aa19bb98a5fd29c15a730cb5064ca128dea19247b896b1a7bdad0b4bccccda9b47366cd1359e740d938e5a47d7bed0501150e8a1623805ac47c489421b1506"
    }
  ],
  "authentication": [
    {
      "type": "Secp256k1SignatureAuthentication2018",
      "publicKey": "did:web:veramo.dev#0405aa19bb98a5fd29c15a730cb5064ca128dea19247b896b1a7bdad0b4bccccda9b47366cd1359e740d938e5a47d7bed0501150e8a1623805ac47c489421b1506"
    }
  ],
  "service": [
    {
      "id": "did:web:veramo.dev#msg",
      "type": "Messaging",
      "serviceEndpoint": "https://veramo.dev/messaging",
      "description": "Handles incoming POST messages"
    }
  ]
}

DID Methods​

Explainer on what a DID method is and links to supported DID Methods page