§ BTCO DID Method

Specification Status: EDITORS DRAFT

Specification Version: v0.2.0 (see Changelog)

Source of Latest Draft: https://github.com/decentralized-identity/labs-ordinals-plus

Information Site: https://ordinals.plus/

Editors:
Brian Richter
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§ Abstract

The BTCO DID Method specification defines a decentralized identifier method that leverages Bitcoin (BTC) Ordinal Theory and Inscriptions to create, resolve, update and deactivate Decentralized Identifiers (DIDs). This method provides a robust foundation for digital identity management directly on the Bitcoin blockchain by using ordinal numbers to uniquely identify satoshis. The specification details the syntax, operations, and security considerations for implementing BTCO DIDs, enabling organizations and individuals to establish verifiable digital identities that are as decentralized, durable, and secure as Bitcoin itself.

§ Overview

The BTCO DID Method provides decentralized identifiers using Bitcoin’s blockchain and ordinal theory. It leverages Bitcoin’s security and network effects while maintaining full compliance with the W3C DID Core Specification.

§ How It Works

The method assigns DIDs to specific satoshis using their ordinal numbers. The DID Document and related data are stored as inscriptions on these satoshis, enabling:

  1. Creation: Register a DID by inscribing it on an unused satoshi
  2. Resolution: Retrieve the DID Document by reading the inscription
  3. Updates: Modify the DID Document through reinscriptions
  4. Deactivation: Mark a DID as inactive using a special reinscription

§ Key Features

§ Purpose

The primary purpose of this method is to:

§ Specification

This section defines the technical specifications for creating, resolving, updating and deactivating BTCO DIDs using Inscriptions.

§ Method Syntax and Structure

The syntax for the BTCO DID method follows the generic DID scheme with the satoshi ordinal number as the method specific identifier:

did:btco:<sat-number>

Where:

Example:

did:btco:1066296127976657
NOTE

Previous versions of this specification described support for name-based and decimal identifiers. Numerical ordinal format is now the only supported format for better interoperability with the Ordinals protocol.

§ DID Document Format

The DID Document MUST be a valid JSON-LD document following this structure:

{
  "@context": [
    "https://www.w3.org/ns/did/v1",
    "https://w3id.org/security/multikey/v1"
  ],
  "id": "did:btco:1066296127976657",
  "verificationMethod": [
    {
      "id": "did:btco:1066296127976657#0",
      "type": "Multikey",
      "controller": "did:btco:1066296127976657",
      "publicKeyMultibase": "z6MkhaXgBZDvotDkL5257faiztiGiC2QtKLGpbnnEGta2doK"
    }
  ],
  "authentication": ["did:btco:1066296127976657#0"],
  "assertionMethod": ["did:btco:1066296127976657#0"]
}

This example shows a basic DID Document. Additional properties defined in the DID Core specification MAY be included, such as:

Key components of this example:

NOTE

Since the DID Document is stored as metadata in the inscription, it can be accessed as a DID Linked Resource using the /meta suffix. For example: did:btco:1066296127976657/0/meta will return the DID Document for the first inscription on the satoshi. See the DID Linked Resources specification for more details about accessing inscription content and metadata.

NOTE

The Multikey context (https://w3id.org/security/multikey/v1) provides a modern verification method type that supports multiple key formats through multibase encoding. This allows for flexible key representation while maintaining compatibility with different cryptographic algorithms.

§ DID Operations

§ Create (Register)

To create a BTCO DID:

  1. Select a satoshi by its ordinal number (e.g., 1066296127976657)
    • MUST be a positive integer
    • MUST be less than or equal to 2099999997689999 (total number of satoshis)
    • MUST NOT already have a valid DID inscription
  2. Generate cryptographic key pair(s)
  3. Create a DID Document following the specified format
  4. Create an inscription with any valid content
  5. Include the DID Document as metadata in CBOR format
  6. Register the inscription on the Bitcoin network

§ Read (Resolve)

Resolution process:

  1. Parse the DID components
    • MUST be a valid BTCO DID format
    • MUST contain a valid satoshi number
  2. Locate the inscription on the specified satoshi using ord
    • Query the satoshi’s inscription history
    • Find the most recent inscription with metadata
  3. Decode and validate the CBOR metadata
    • MUST contain a valid DID Document
    • Document id MUST match the requested DID
  4. Return the resolved DID Document

Possible errors:

Success response format:

{
  "didDocument": {
    // The resolved DID Document
  },
  "metadata": {
    "created": "<timestamp>",
    "updated": "<timestamp>",
    "deactivated": false,
    "nextVersionId": "<DID Linked Resource Identifier>",
    "versionId": "<DID Linked Resource Identifier>",
    "equivalentId": ["<alternative DID URLs>"]
  }
}
NOTE

The versionId and nextVersionId fields use DID Linked Resource identifiers (e.g., did:btco:1066296127976657/0) to reference specific versions of the DID Document. This format allows direct access to historical DID Document versions through the DID Linked Resources specification.

Error response format:

{
  "error": "<error code>",
  "message": "<human readable message>",
  "details": {
    // Additional error context
  }
}

§ Update

To update a BTCO DID:

  1. Create new DID Document
  2. Sign the update using an authorized verification method
  3. Create an inscription with any valid content
  4. Include updated DID Document as CBOR metadata
  5. Register as a reinscription on the target satoshi

§ Deactivate

To deactivate a BTCO DID:

  1. Create a minimal DID Document containing:
{
  "@context": [
    "https://www.w3.org/ns/did/v1",
    "https://w3id.org/did-resolution/v1"
  ],
  "id": "did:btco:1066296127976657",
  "deactivated": true
}
  1. Include this document as CBOR metadata in the inscription
  2. Register as a reinscription on the target satoshi
  3. The inscription content can be any valid data
NOTE

The deactivated state is defined in the DID Resolution specification and will be recognized by standard DID resolvers.

§ Cryptographic Operations

§ Control and Key Management

The BTCO DID method ties DID control directly to Bitcoin UTXO ownership:

The DID Document itself can contain multiple verification methods as defined in the DID Core specification. These keys:

NOTE

While Bitcoin UTXO recovery mechanisms are outside the scope of this specification, DID Document keys can be recovered through a DID Document update by the UTXO owner.

§ Supported Algorithms

The method supports multiple cryptographic suites through the Multikey verification method type:

The Data Integrity proof suite MUST be used for all cryptographic operations. This provides:

§ Key Management

Implementations MUST:

§ Security Considerations

Additional security requirements:

§ Privacy Considerations

Enhanced privacy measures:

§ Inscription Content

BTCO DID inscriptions can contain any valid data in their content. The DID operations (create, update, deactivate) are controlled through the inscription metadata, while the content remains unrestricted for application-specific uses.

§ Inscription Requirements

This DID method relies on the Ordinals protocol and the ord client for inscription handling:

NOTE

All inscription creation, validation, and ordering follows the Ordinals protocol as implemented by the reference ord client. This specification does not modify or extend the underlying inscription mechanisms.

§ DID Document Storage

§ Inscription Order

When resolving a DID:

For detailed information about inscription mechanics, refer to the Ordinals protocol documentation.

§ Terminology

Bitcoin (BTC):
The original and most widely adopted blockchain network, known for its decentralized and immutable nature.
Decentralized Identifiers (DIDs):
A type of globally unique identifier that enables verifiable, decentralized digital identity, as defined by the W3C DID Core specification.
DID Document:
A document containing information related to a DID, such as verification methods and service endpoints.
Inscription:
Arbitrary content added to BTC satoshis (sats) to create BTC-native digital artifacts.
Ordinal Number:
A unique integer between 0 and 2099999997689999 that identifies a specific satoshi based on the order in which it was mined.
Ordinal Theory:
A numbering scheme for satoshis that allows for individual satoshis to be tracked and inscribed with data.
Verification Method:
A mechanism that can be used to verify a proof, such as a digital signature or encryption.
Service Endpoint:
A network address at which services can be accessed using a DID.
Controller:
The entity that has the capability to make changes to a DID Document.

§ Version Changelog

§ v0.2.0 (Current)

§ Breaking Changes

  1. Identifier Format: The method-specific identifier now only accepts ordinal numbers. Name-based identifiers (e.g., “bwtowpglzpd”) and decimal formats (e.g., “53585.3880634312”) are no longer supported. This change ensures consistent identifier resolution and improved interoperability.

  2. Migration: DIDs created using name-based or decimal identifiers in v0.1.0 should be migrated to numerical ordinal format. The migration process involves:

    • Creating a new DID using the ordinal number format
    • Transferring control to the new DID
    • Deactivating the old DID

  3. Deactivation Method: Changed from using inscription content (“🔥”) to using metadata for deactivation status. This provides better consistency with other operations and allows inscription content to be used for application-specific purposes.

§ v0.1.0

§ Test Vectors

§ Valid DIDs

did:btco:0
did:btco:2099999997689999
did:btco:1066296127976657

§ Invalid DIDs

did:btco:bwtowpglzpd              # Invalid: Uses name format (v0.1.0)
did:btco:53585.3880634312         # Invalid: Uses decimal format (v0.1.0)
did:btco:-1                       # Invalid: Negative number
did:btco:2099999997690000        # Invalid: Exceeds maximum satoshi number
did:btco:1.5                     # Invalid: Not an integer
did:btco:abc123                  # Invalid: Not a number

§ Example DID Document

{
  "@context": [
    "https://www.w3.org/ns/did/v1",
    "https://w3id.org/security/data-integrity/v2"
  ],
  "id": "did:btco:1066296127976657",
  "verificationMethod": [
    {
      "id": "did:btco:1066296127976657#0",
      "type": "Multikey",
      "controller": "did:btco:1066296127976657",
      "publicKeyMultibase": "z6MkhaXgBZDvotDkL5257faiztiGiC2QtKLGpbnnEGta2doK"
    }
  ],
  "authentication": ["did:btco:1066296127976657#0"],
  "assertionMethod": ["did:btco:1066296127976657#0"]
}
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