AMO is a platform on which various parties including corporations and individual drivers can trade automotive data. AMO blockchain is a blockchain technology supporting AMO platform and AMO ecosystem, specialized on uploading and trading data parcels or access rights on the data. AMO DID method is a subset of AMO blockchain feature set, which provides a concrete specification for AMO-specific DID and appropriate operations. AMO DID method is valid for AMO blockchain mainnet only. Thus it is necessary to set up a separate DID resolution method to use any AMO blockchain testnet.

ABNF notation for DID used in AMO DID Method is as follows:

amo-did = "did" ":" "amo" ":" address
address = 40addrchar
addrchar = DIGIT / "A" / "B" / "C" / "D" / "E" / "F"

Method name for AMO DID Method is amo. address part corresponds to an account address in AMO blockchain, which is written in 40 uppercase hexadecimal digits.

Since AMO blockchain is based on its own account system, AMO DID method is intended to use the same account system. However, as far as the DID format is valid, it is possible to generate any DID address without considering actual AMO blockchain account. Hence, in its extreme case, it is possible to generate a random 160-bit binary stream and convert it to an uppercase hexadecimal representation with 40 characters.

When generating a new DID based on an AMO blockchain account, one would execute either of the following procedures:

1. Generate a new AMO blockchain address according to Account address described in AMO blockchain protocol. Grab the account address address and form a DID as a concatenation of did:amo: and address.
2. Obtain an account address address from existing AMO blockchain account. Form a DID as a concatenation of did:amo: and address.

The followings are valid AMO DIDs:

did:amo:70EAD5B53B11DFE78EC8CF131D7960F097D48D70
did:amo:0000000000000000000000000000000000000000

The followings are not valid AMO DIDs:

did:amo:70ead5b53b11dfe78ec8cf131d7960f097d48d70 (lower case)
did:amo:70EAD5B53B11DFE78EC8CF131D7960F097D48D (length error)

In AMO DID method, a DID document is represented in the JSON-LD format. When represented in JSON-LD format, @context property must have the following entry:

"@context": "https://www.w3.org/ns/did/v1"

An AMO DID document must have the following top-level properties:

• id
• verificationMethod
• authentication

There can be following optional top-level properties.

• controller
• assertionMethod

Identifier, i.e. DID, which references to this DID document is represented by a id property, which is described in AMO DID Scheme.

Verification method is represented by a verificationMethod property. Since an AMO blockchain account has a pair of private and public keys, verificationMethod property must have at least one entry as the first one. id of the first verification method must be a concatenation of id of the DID subject and #keys-1. As described in AMO blockchain protocol, AMO blockchain uses ECDSA over NIST P256 curve. A corresponding public key is described publicKeyJwk property. Properties of publicKeyJwk is as described in JSON Web Key 2020. controller property must be the same as the DID subject.

"verificationMethod": [{
  "id": "did:amo:addressinhex#keys-1",
  "type": "JsonWebKey2020",
  "controller": "did:amo:addressinhex",
  "publicKeyJwk": {
    "kty": "EC",
    "crv": "P-256",
    "x": ...,
    "y": ...
  }
}]

In AMO blockchain protocol, the public key of an account is represented by an uncompressed form with 04 prefix. x and y properties of publicKeyJwk are extracted from this uncompressed form as follows:

• x = base64(pubkey[1:33])
• y = base64(pubkey[33:65])

NOTE: This property may be changed to an optional property.

NOTE: Currently, there is no mechanism for key rotating and revocation.

Authentication relation of a verification method is represented by an authentication property. authentication property must have a reference to the first verification method as described in Verification Method. For example, did:amo:addressinhex#keys-1.

NOTE: This property may be changed to an optional property.

Assertion relation of a verification method is represented by an assertionMethod property. assertionMethod property must have a reference to the first verification method as described in Verification Method. For example, did:amo:addressinhex#keys-1.

NOTE: This property may be changed to an optional property.

controller property is optional.

{
  "@context": "https://www.w3.org/ns/did/v1",
  "id": "did:amo:70EAD5B53B11DFE78EC8CF131D7960F097D48D70",
  "controller": "did:amo:0687D766FF0563B86BFF078B7F560AFC070C81AD",
  "verificationMethod": [{
    "id": "did:amo:70EAD5B53B11DFE78EC8CF131D7960F097D48D70#keys-1",
    "type": "JsonWebKey2020",
    "controller": "did:amo:70EAD5B53B11DFE78EC8CF131D7960F097D48D70",
    "publicKeyJwk": {
      "kty": "EC",
      "crv": "P-256",
      "x": ...,
      "y": ...
    }
  }],
  "authentication": [
    "did:amo:70EAD5B53B11DFE78EC8CF131D7960F097D48D70#keys-1"
  ],
  "assertionMethod": [
    "did:amo:70EAD5B53B11DFE78EC8CF131D7960F097D48D70#keys-1"
  ]
}

Transmit a did.claim tx to the AMO blockchain mainnet. Form a tx body as follows:

{
  "target": _amo_did_,
  "document": _amo_did_document_
}

_amo_did_ is a DID for a newly created DID document _amo_did_document_.

See did.claim tx for more detail.

See Transmitting tx for information about sending a signed tx to AMO blockchain.

Perform ABCI query for did store to the AMO blockchain mainnet. Form a query message as follows:

{
  "path": "/did",
  "data": _query_data_
}

_query_data_ is formed as follows:

1. construct a double-quoted string containing an AMO DID
   "did:amo:70EAD5B53B11DFE78EC8CF131D7960F097D48D70" for did:amo:70EAD5B53B11DFE78EC8CF131D7960F097D48D70
2. convert the result of step 1 using hex conversion
   226469643A616D6F3A0A3730454144354235334231314446453738454338434631333144373936304630393744343844373022

See ABCI query for information about sending an ABCI query to AMO blockchain.

Transmit a did.claim tx to the AMO blockchain mainnet. Form a tx body as follows:

{
  "target": _amo_did_,
  "document": _amo_did_document_
}

_amo_did_ is a DID for an existing DID document, which is replaced by a new document _amo_did_document_.

See did.claim tx for more detail.

See Transmitting tx for information about sending a signed tx to AMO blockchain.

Transmit a did.dismiss tx to the AMO blockchain mainnet. Form a tx body as follows:

{
  "target": _amo_did_
}

_amo_did_ is a DID for an existing DID document to be deactivated.

See did.dismiss tx for more detail.

See Transmitting tx for information about sending a signed tx to AMO blockchain.

In order to interact with AMO blockchain, one needs to find a RPC node of the chain, and form an appropriate RPC message and send it to the node. One could set up its own AMO blockchain node with the RPC feature on. However, there is a public RPC node open to anybody in the world: https://rpc.amolabs.io.

NOTE: rpc.amolabs.io serves on 443 (https) port instead of default 26657 port of tendermint.

The chain ID for AMO blockchain mainnet is amo-cherryblossom-01.

Send signed tx to one of AMO blockchain RPC nodes. See AMO blockchain protocol for more detail.

Send ABCI query message to one of AMO blockchain RPC nodes. See AMO client RPC spec for more detail.

Instead of querying a AMO DID document to an AMO blockchain RPC node, it is possible to query it via AMO blockchain explorer. For example, in order to get DID document for a DID did:amo:70EAD5B53B11DFE78EC8CF131D7960F097D48D70, send an HTTP request to the following URL.

https://api.explorer.amolabs.io/chain/amo-cherryblossom-01/dids/70EAD5B53B11DFE78EC8CF131D7960F097D48D70

Since the public AMO blockchain explorer server has a persistent DNS name, it is also possible to use the above URL as an alias for the DID did:amo:70EAD5B53B11DFE78EC8CF131D7960F097D48D70. In this case, DID resolution is a simple HTTP request and the response is the DID document for the requested DID.

An attacker must solve a computationally hard problem to forge a private key of the corresponding account in order to register a DID document for an arbitrary DID.

An attacker must solve a computationally hard problem to forge a private key of the corresponding account in order to update or deactivate a DID document not controlled by the attacker.

An attacker must subverts a Replay Preventer of AMO blockchain in order to replay any tx previously sent to the blockchain by a legitimate user.

It is inherent that an AMO blockchain account has a fixed address for a lifetime of the account. It is inevitable to expose the account address while interacting with AMO blockchain (or many other blockchains). Thus, this should not be considered to be an additional privacy problem raised by this DID method.

Since there is no published information about the real-world owner of an AMO blockchain account, a user's real world identity remains safe even if the account address is exposed.

Anyone who can read a public AMO blockchain data can track activies of an AMO blockchain account. Thus all activies can be linkable to a specific AMO blockchain account. However, this is an inherent property of AMO blockchain (or many other blockchains). Thus, this should not be considered to be an additional privacy problem raised by this DID method.