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did:nostr

Thought experiment around bringing dids to nostr.

Why?

I have no idea whether this will work, or if it's a good idea. What has me interested is:

  • Could provide a means for key rotation while using the same pubkey as identity
  • Could allow for interop between different protocols / systems
  • Could enable use of Verifiable Credentials
    • e.g. CashApp could issue cashtag Verifiable Credentials to DIDs. This would basically allow people to have a "blue checkmark" or, more generally speaking, some trusted way to say "this pubkey is linked to this cashtag".
    • e.g. could introduce stuff like payments on nostr via CashApp simply by having a pubkey present their cashtag VC to a CashApp api endpoint. VC can be used as a form of authentication, since the VC was issued by CashApp
  • Could allow for less reliance on DNS if desired

Brain Dump

DIDs

DIDs, like URLs are fully qualified URIs. Similar to a URL, DIDs can be resolved. resolving a URL like https://snort.social/ returns html. So what does resolving a DID return? A DID document

DID Documents

What is a DID document? it's a JSON object that contains information about the DID e.g.

  • how to contact this DID,
  • pubkeys this DID uses to sign messages,
  • asymmetric encryption keys that can be used to create shared keys and encrypt messages for the DID. Example:
{
  "@context": [
    "https://www.w3.org/ns/did/v1",
  ],
  "id": "did:nostr:e2bdaa90e96a4fafb9f1c36f9b378e4bbd6fea26e5d47063e7b30aa15de37d48",
  "verificationMethod": [
    {
      "id": "did:nostr:e2bdaa90e96a4fafb9f1c36f9b378e4bbd6fea26e5d47063e7b30aa15de37d48#nip06-0",
      "type": "SchnorrSecp256k1VerificationKey2019",
      "controller": "did:nostr:e2bdaa90e96a4fafb9f1c36f9b378e4bbd6fea26e5d47063e7b30aa15de37d48",
      "publicKeyHex": "e2bdaa90e96a4fafb9f1c36f9b378e4bbd6fea26e5d47063e7b30aa15de37d48"
    }
  ],
  "service": [
    {
      "id": "did:nostr:e2bdaa90e96a4fafb9f1c36f9b378e4bbd6fea26e5d47063e7b30aa15de37d48#nostr-relays",
      "type": "Relay",
      "serviceEndpoint": ["wss://relay.damus.io", "wss://relay.nostr.info"]
    },
    {
      "id": "did:nostr:e2bdaa90e96a4fafb9f1c36f9b378e4bbd6fea26e5d47063e7b30aa15de37d48#ln",
      "type": "LightningNode",
      "serviceEndpoint": "ip://024bfaf0cabe7f874fd33ebf7c6f4e5385971fc504ef3f492432e9e3ec77e1b5cf@52.1.72.207:9735"
    }
  ],
  "keyAgreement": [
    {
      "id": "did:nostr:e2bdaa90e96a4fafb9f1c36f9b378e4bbd6fea26e5d47063e7b30aa15de37d48#keyagreement",
      "type": "X25519KeyAgreement2023",
      "controller": "did:nostr:e2bdaa90e96a4fafb9f1c36f9b378e4bbd6fea26e5d47063e7b30aa15de37d48",
      "publicKeyHex": "75d92cea4ab8ef28a0a14acf103d6b8a2bb026120d62d1817fa5a4b11f534038"
    }
  ]
}

💡 TODO: think of more service examples

💡 TODO: figure out id property for keyAgreement

so what do the properties in the DID document mean?

property description notes
verificationMethod includes crypto keys that can be used for various purposes, such as to verify digital signatures the key shown in the example above happens to be the decoded nostr pubkey
service lists services that can be used to interact with a DID the example includes the nostr relays that this DID publishes to. Could also include any other service e.g. a lightning node
keyAgreement lists keys that can be used to generate shared keys for encryption/decryption purposes

💡 there are several other properties that can exist on DID documents. more info on that here

NIP-9325

⚠️ WIP ⚠️

This NIP proposes the following:

  • how to generate a nostr did
  • a new event kind 9325 for publishing, patching, and recovering a DID.
  • how to resolve a nostr DID

DID generation

did:nostr:<nostr_hex_pubkey>

  1. generate a new (or use an existing) nostr pubkey according to BIP340 as mentioned in nip01. nostr_hex_pubkey is represented as 32-bytes lowercase hex-encoded public key
  2. prefix the nostr_hex_pubkey with did:nostr:

Example

did:nostr:41e791de6a6f6f0b3c820c2db179c0679e2c228ae6ecb9583cb48b3e1ff354b6

💡 reference implementation

💡 if desired nostr dids can be displayed using the bech32 encoded npub format described in nip19 e.g. did:nostr:npub1u2.... As stated in nip19: The bech32 encodings should not be used to represent a did in nostr events.

Deriving base DID Document

the base DID document can be derived without sending a publish message to a relay. It's not all that useful in and of itself, but forms the foundation of DID resolution.

💡 reference implementation

💡 TODO: write out steps to derive base DID Document by reading reference implementation

// from example.ts in reference implementation
const did = pubKeyToDid(kp.public);
console.log(deriveDidDoc(did));

Output

{
  "id": "did:nostr:41e791de6a6f6f0b3c820c2db179c0679e2c228ae6ecb9583cb48b3e1ff354b6",
  "verificationMethod": [
    {
      "id": "did:nostr:41e791de6a6f6f0b3c820c2db179c0679e2c228ae6ecb9583cb48b3e1ff354b6#nip06-0",
      "type": "SchnorrSecp256k1VerificationKey2019",
      "controller": "did:nostr:41e791de6a6f6f0b3c820c2db179c0679e2c228ae6ecb9583cb48b3e1ff354b6",
      "publicKeyHex": "41e791de6a6f6f0b3c820c2db179c0679e2c228ae6ecb9583cb48b3e1ff354b6"
    }
  ]
}

💡 the verificationMethod in the example above is a schnorr pubkey. SchnorrSecp256k1VerificationKey2019 is used to describe the type of verification method. Honestly not entirely sure what the motiviation is behind including the year (aka 2019).

DID Event

image

This event can be used to publish, patch, and recover a DID. every 9325 message should contain the o (e.g op) and d (e.g. did) tags

{
  "kind": 9325,
  "tags": [
    ["o", "publish | patch | recover"],
    ["d", "did:nostr:e2bdaa90e96a4fafb9f1c36f9b378e4bbd6fea26e5d47063e7b30aa15de37d48"]
  ]
}

publish

Event

{
  "kind": 9325,
  "pubkey": "e3932a8cd4ec81e1e9a41467470ec9db817accf21e1e8b939525e84da6786d9a",
  "created_at": 1676957260,
  "tags": [
    ["d","did:nostr:e3932a8cd4ec81e1e9a41467470ec9db817accf21e1e8b939525e84da6786d9a"],
    ["o","publish"]
  ],
  "content": "{\"r\":\"683c867bf3dc5e7993fdd0715771d36eb6f00b8a8645795c332246ea5f19c7d5\",\"patches\":[{\"op\":\"add\",\"path\":\"/service\",\"value\":[{\"id\":\"did:nostr:e3932a8cd4ec81e1e9a41467470ec9db817accf21e1e8b939525e84da6786d9a#nostr-relays\",\"type\":\"NostrRelay\",\"serviceEndpoint\":[\"wss://relay.damus.io\"]}]}]}",
  "sig": "b1bae7a64d84ce63e40dfa24d299892116694ae71215f357ddad0a0091455e0b985b45ccca6f9354223dc3f0243a9eabcb6d874ff85fac7051493fee8aab2ef9"
}
  • should only ever be 1 publish event for a given DID
  • should be the first event of kind 9325 for a given DID
  • the o tag should have a value of publish
  • the d tag should be present and contain the relevant DID
  • content is a stringified json object that contains the following properties:
Property Description
r double hashed (sha256) encoded recovery pubkey
patches an array of JSON patch ops that are applied on top of the base DID Document

Integrity Checks

  • event.pubkey should match the id of the DID found in the d tag.
  • standard nostr sig verification

recover

Event

{
  "content": "{\"r\":\"0df32bb15f48f60c5d7e035bdfbc67507a8576109a422dd860ad1a7b4935b3e6\"}",
  "created_at": 1676957711,
  "kind": 9325,
  "pubkey": "b424a3e0ea03a1450feef4cdba3dd74892c3e18726f079f89db42d597dfceb4c",
  "tags": [
    ["d","did:nostr:89abca8adb7d5db8a4b4e90b0c0eb97dc6f3a957fc219a83bf925fb9c7bd4331"],
    ["o", "recover"],
    ["e", "bd513634c49754383d9d4110ebeaa1433467c5b70da7ae2d2873cabcd5445451", "wss://relay.damus.io", "reply"]
  ],
  "sig": "1f3fdaf79dcf9fb7ab51834c80b28abc5e6a3850f0185bb5b616f4a5e133f188dc609be10462e551ea984fe403a32a4b0b8b492d0c9c45f63d4fdd4d38d8c46d",
}
  • the o tag should have a value of recover
  • the d tag should be present and contain the relevant DID
  • should contain a nip10 marked e tag pointing to the most recent event of kind 9325 for the relevant DID
    • 💡 If more than one e tag is allowed, it may be helpful to include an additional marked root e tag that points back to the initial publish event
    • 💡 If more than one e tag is allowed, it may be helpful to include an additional marked mention e tag that points back to the most recent recover event for the relevant DID
  • content is a stringified json object that contains the following properties:
Property Description
r new double hashed (sha256) recovery key

💡 Note: any r should not be used more than once. Recovering should always include a new r that can be used for subsequent recoveries

Integrity Checks

  • sha256(sha256(event.pubkey)) should match JSON.parse(previousEvent.content).r of the most recent recover event if one exists or the initial publish event if no other recover events exist

patch

Event

{
  "kind": 9325,
  "tags": [
    ["d", "did:nostr:e2bdaa90e96a4fafb9f1c36f9b378e4bbd6fea26e5d47063e7b30aa15de37d48"]
    ["e", "event id of most recent 9325 event for did"]
    ["o", "patch"],
  ],
  "content": "{\"patches\":[{\"op\":\"add\",\"path\":\"/service\",\"value\":[{\"id\":\"did:nostr:e2bdaa90e96a4fafb9f1c36f9b378e4bbd6fea26e5d47063e7b30aa15de37d48#nostr-relays\",\"type\":\"NostrRelay\",\"serviceEndpoint\":[\"wss://relay.damus.io\"]}]}]}"
}
  • content is a stringified json object that contains the following properties:
Property Description
patches an array of JSON patch ops

Resolving

💡 WIP reference implementation

Given a DID (e.g. did:nostr:e2bdaa90e96a4fafb9f1c36f9b378e4bbd6fea26e5d47063e7b30aa15de37d48):

  • Derive the base DID document by following these steps
  • fetch all events of kind 9325 for the DID being resolved
  • order the events using created_at
  • ensure that first event is a publish. perform integrity checks listed here
  • for each event thereafter:
    • ensure that the id provided in the marked event tag matches the id of the previous event
    • if patch: apply patches to DID doc
    • if recover: perform integrity checks listed here
      • optional: include revealed pubkey as verificationMethod in DID doc

Considerations

  • clients or relays making use of the #d tag should perform necessary integrity checks before trusting that the event came from the listed DID
  • if possible, relays should perform integrity checks on a 9325 event prior to storing it