WHO SMART Trust
1.5.0 - release

WHO SMART Trust, published by WHO. This guide is not an authorized publication; it is the continuous build for version 1.5.0 built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of https://github.com/WorldHealthOrganization/smart-trust/tree/v1.5.0-release-candidate and changes regularly. See the Directory of published versions

## DID Trustlist v1 (deprecated)

#### DID Document v1.0 (deprecated)

The unified format is based on the Decentralized Identifiers (DIDs) v1.0 specification. DIDs are globally unique identifier in the form of URIs. The URI scheme includes a method name which corresponds to a standard method by which a DID Document can be resolved. This DID Document is a structured JSON-LD which captures each existing public key (regardless of X.509 or JWK format used) by the members of a trust network in a common format. It allows additional metadata (such as intended purpose and key identifiers) to be added to existing keys with changing the underlying keys themselves​. It provides means to publish and cryptographically sign a master lists of keys recognized used by a trust network.

The unified format DID method selected is did:web, a method to retrieve DID Documents via existing web (https) infrastructure​. ​The did:web identifiers have the form `<DOMAIN NAME>:<PATH COMPONENT 1>:...: <PATH COMPONENT N>`​. Resolution is accomplished by https GET against the URL which is formed from this identifier by​ `https://​DOMAIN NAME/PATH COMPONENT 1/.../PATH COMPONENT N/did.json`. For example did:web:example.com:my:path would resolve a DID Document from the URL `https://example.com/my/path/did.json`​. Additional did methods may be supported in the future.

The DID Document itself should have:​

- an ‘id’ field which is the DID itself and represents the DID Subject, in this case the trust list
- a list of public keys within the ‘verificationMethod’ field​
- an optional signature via a ‘proof’ field​

The verificationMethod array represents the individual signing keys associated with issuers within the entity represented by the DID Subject, an includes:

- an `id` field which is a DID URL composed of the DID for this DID Document and key ID as ​DID#key
- controller of the public key, which can be current document (in case of publishing a key by a trust network member) or the source of the public key in case of an aggregator
- the public key JWK, including the key's x509 and chain of trust to Root Certificate Authority​

The DID Document itself can be signed with addition of a ‘proof’ block containing signature details and key used for verification.

For more information regarding the DID Document format for a Trust List specification, see WHO DDCC Trust List Specification documentation. For an example of a signed DID Document, see Appendix A of the documentation.