# `x/did`

The Decentralized Identity module is responsible for managing native Sonr Accounts, their derived wallets, and associated user identification information. This module now incorporates UCAN (User Controlled Authorization Networks) for enhanced authorization and access control.

## State

The DID module maintains several key state structures:

### Controller State

The Controller state represents a Sonr DWN Vault. It includes:
- Unique identifier (number)
- DID
- Sonr address
- Ethereum address
- Bitcoin address
- Public key
- Keyshares pointer
- Claimed block
- Creation block

### Assertion State

The Assertion state includes:
- DID
- Controller
- Subject
- Public key
- Assertion type
- Accumulator (metadata)
- Creation block

### Authentication State

The Authentication state includes:
- DID
- Controller
- Subject
- Public key
- Credential ID
- Metadata
- Creation block

### Verification State

The Verification state includes:
- DID
- Controller
- DID method
- Issuer
- Subject
- Public key
- Verification type
- Metadata
- Creation block

## State Transitions

State transitions are triggered by the following messages:
- LinkAssertion
- LinkAuthentication
- UnlinkAssertion
- UnlinkAuthentication
- ExecuteTx
- UpdateParams

## Messages

The DID module defines the following messages:

1. MsgLinkAuthentication
2. MsgLinkAssertion
3. MsgExecuteTx
4. MsgUnlinkAssertion
5. MsgUnlinkAuthentication
6. MsgUpdateParams

Each message triggers specific state machine behaviors related to managing DIDs, authentications, assertions, and module parameters. These messages now also involve UCAN authorization checks where applicable.

## Query

The DID module provides the following query endpoints:

1. Params: Query all parameters of the module, including UCAN-related parameters.
2. Resolve: Query the DID document by its ID
3. Sign: Sign a message with the DID document
4. Verify: Verify a message with the DID document

## Params

The module parameters include:
- Allowed public keys (map of KeyInfo)
- Conveyance preference
- Attestation formats
- UCAN Authorization Parameters:
  - `UcanPermissions`: Specifies the required UCAN permissions for various actions within the module.

## Client

The module provides gRPC and REST endpoints for all defined messages and queries.

## UCAN Authorization

This module utilizes UCAN (User Controlled Authorization Networks) to provide a decentralized and user-centric authorization mechanism. UCANs are self-contained authorization tokens that allow users to delegate specific capabilities to other entities without relying on a central authority.

### UCAN Integration

- The module parameters include a `UcanPermissions` field that defines the default UCAN permissions required for actions within the module.
- Message handlers in the `MsgServer` perform UCAN authorization checks by:
  - Retrieving the UCAN permissions from the context (injected by a middleware).
  - Retrieving the required UCAN permissions from the module parameters.
  - Verifying that the provided UCAN permissions satisfy the required permissions.
- A dedicated middleware is responsible for:
  - Parsing incoming requests for UCAN tokens.
  - Verifying UCAN token signatures and validity.
  - Extracting UCAN permissions.
  - Injecting UCAN permissions into the context.
- UCAN verification logic involves:
  - Checking UCAN token signatures against the issuer's public key (resolved via the `x/did` module).
  - Validating token expiration and other constraints.
  - Parsing token capabilities and extracting relevant permissions.

## Future Improvements

Potential future improvements could include:
1. Enhanced privacy features for DID operations, potentially leveraging UCAN capabilities for privacy-preserving authorization.
2. Integration with more blockchain networks
3. Support for additional key types and cryptographic algorithms
4. Improved revocation mechanisms for credentials, assertions, and UCAN tokens.

## Tests

Acceptance tests should cover all major functionality, including:
- Creating and managing DIDs
- Linking and unlinking assertions and authentications
- Executing transactions with DIDs
- Querying and resolving DIDs
- Parameter updates

## Appendix

### Account

An Account represents a user's identity within the Sonr ecosystem. It includes information such as the user's public key, associated wallets, and other identification details.

### Decentralized Identifier (DID)

A Decentralized Identifier (DID) is a unique identifier that is created, owned, and controlled by the user. It is used to establish a secure and verifiable digital identity.

### Verifiable Credential (VC)

A Verifiable Credential (VC) is a digital statement that can be cryptographically verified. It contains claims about a subject (e.g., a user) and is issued by a trusted authority.

### Key Types

The module supports various key types, including:
- Role
- Algorithm (e.g., ES256, EdDSA, ES256K)
- Encoding (e.g., hex, base64, multibase)
- Curve (e.g., P256, P384, P521, X25519, X448, Ed25519, Ed448, secp256k1)

### JSON Web Key (JWK)

The module supports JSON Web Keys (JWK) for representing cryptographic keys, including properties such as key type (kty), curve (crv), and coordinates (x, y) for EC and OKP keys, as well as modulus (n) and exponent (e) for RSA keys.
