ethr-did

Ethr-DID Library

DID Specification | ERC-1056 | Getting Started

This library conforms to ERC-1056 and is intended to use Ethereum addresses as fully self-managed Decentralized Identifiers (DIDs), it allows you to easily create and manage keys for these identifiers. It also lets you sign standards compliant JSON Web Tokens (JWT) that can be consumed using the DID-JWT library.

This library can be used to create a new ethr-did identifier. It allows ethr-did identifiers to be represented as an object that can perform actions such as updating its DID document, signing messages, and verifying messages from other DIDs.

Use this if you are looking for the easiest way to start using ethr-did identifiers, and want high-level abstractions to access its entire range of capabilities. It encapsulates all the functionality of ethr-did-resolver and ethr-did-registry.

A DID is an Identifier that allows you to lookup a DID document that can be used to authenticate you and messages created by you.

Ethr-DID provides a scalable identity method for public keys and Ethereum addresses that gives them the ability to collect on-chain and off-chain data. Because Ethr-DID allows any Ethereum key pair to become a DID, it is more scalable and privacy-preserving than smart contract based identity methods, like our previous Proxy Contract.

This particular DID method relies on the Ethr-Did-Registry. The Ethr-DID-Registry is a smart contract that facilitates public key resolution for off-chain (and on-chain) authentication. It also facilitates key rotation, delegate assignment and revocation to allow 3rd party signers on a key's behalf, as well as setting and revoking off-chain attribute data. These interactions and events are used in aggregate to form a DID's DID document using the Ethr-Did-Resolver .

An example of a DID document resolved using the ethr-did-resolver:

{
  '@context': [
    'https://www.w3.org/ns/did/v1',
    'https://w3id.org/security/suites/secp256k1recovery-2020/v2'
  ],
  id: 'did:ethr:0xb9c5714089478a327f09197987f16f9e5d936e8a',
  verificationMethod: [
    {
      id: 'did:ethr:0xb9c5714089478a327f09197987f16f9e5d936e8a#controller',
      type: 'EcdsaSecp256k1RecoveryMethod2020',
      controller: 'did:ethr:0xb9c5714089478a327f09197987f16f9e5d936e8a',
      blockchainAccountId: 'eip155:1:0xb9c5714089478a327f09197987f16f9e5d936e8a'
    }
  ],
  assertionMethod: [
    'did:ethr:0xb9c5714089478a327f09197987f16f9e5d936e8a#controller'
  ],
  authentication: [
    'did:ethr:0xb9c5714089478a327f09197987f16f9e5d936e8a#controller'
  ]
}

On-chain refers to something that queried or modified with a transaction on a blockchain, while off-chain can refer to anything from temporary payment channels to IPFS and regular web services.

It supports the proposed Decentralized Identifiers spec from the W3C Credentials Community Group.

DID Method

A "DID method" is a specific implementation of a DID scheme that is identified by a method name. In this case, the method name is ethr, and the method identifier is an Ethereum address or a secp256k1 publicKey.

To encode a DID for an Ethereum address, simply prepend did:ethr:

For example:

• DID based on an ethereum address: did:ethr:0xf3beac30c498d9e26865f34fcaa57dbb935b0d74
• DID based on a key: did:ethr:0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798

Configuration

import { EthrDID } from 'ethr-did'

const chainNameOrId = 1 // mainnet
const provider = InfuraProvider("<infura project ID>", chainNameOrId)
const ethrDid = new EthrDID({ identifier: '0x...', privateKey: '...', provider, chainNameOrId })

key	description	required
identifier	Ethereum address, public key or a full did:ethr representing Identity	yes
chainNameOrId	The name or chainId of the ethereum network (defaults to 'mainnet')	no, but recommended
registry	registry address (defaults to 0xdca7ef03e98e0dc2b855be647c39abe984fcf21b)	no
provider	web3 provider	either provider or web3 or rpcUrl
web3	preconfigured web3 object	either provider or web3 or rpcUrl
rpcUrl	JSON-RPC endpoint url	either provider or web3 or rpcUrl
signer	JWS Signing function	either signer or privateKey
txSigner	Ethers.js Signer	either txSigner or privateKey
privateKey	Hex encoded private key	yes*

Important notes on keys and signers

If privateKey is specified, then signer and txSigner don't need to be used. Otherwise, a txSigner is required to perform CRUD operations on the DID document, and a signer is required to sign JWTs. To generate valid JWT, the signer must use one of the keys listed in the DID document. To be able to perform CRUD operations, the txSigner must be backed by the key that governs the owner property. See https://github.com/uport-project/ethr-did-registry#looking-up-identity-ownership

Notes

Readonly ethr-did

An instance created using only an address or publicKey (without access to a privateKey or to signers) can only be used to encapsulate an external ethr-did . This instance will not have the ability to sign anything, but it can be used for a subset of actions:

• provide its own address (ethrDid.address)
• provide the full DID string (ethrDid.did)
• lookup its owner await ethrDid.lookupOwner()
• verify a JWT await ethrDid.verifyJwt(jwt)

Multiple ethereum networks

EthrDid can be configured to control a DID on any ethereum network. To do this, you mush specify the chainNameOrId during construction. Example:

console.log(new EthrDID({ identifier: '0xb9c5714089478a327f09197987f16f9e5d936e8a', chainNameOrId: 'goerli' }).did)
// did:ethr:goerli:0xB9C5714089478a327F09197987f16f9E5d936E8a

If this property is not specified, then the library will attempt to infer it from the provider configuration or from the identifier if it is specified as a DID. But, be warned that it may lead to inconsistencies since the inference is not perfect. It is highly recommended that you use a chainNameOrId property to match the provider.

More

See the guide to get a better idea about the capabilities of this lib. And, of course, make sure to familiarize yourself with the did:ethr spec