Copyright © 2021 W3C® (MIT, ERCIM, Keio, Beihang). W3C liability, trademark and permissive document license rules apply.
Decentralized identifiers (DIDs) are a new type of identifier that enables verifiable, decentralized digital identity. A DID refers to any subject (e.g., a person, organization, thing, data model, abstract entity, etc.) as determined by the controller of the DID. In contrast to typical, federated identifiers, DIDs have been designed so that they may be decoupled from centralized registries, identity providers, and certificate authorities. Specifically, while other parties might be used to help enable the discovery of information related to a DID, the design enables the controller of a DID to prove control over it without requiring permission from any other party. DIDs are URIs that associate a DID subject with a DID document allowing trustable interactions associated with that subject.
Each DID document can express cryptographic material, verification methods, or services, which provide a set of mechanisms enabling a DID controller to prove control of the DID. Services enable trusted interactions associated with the DID subject. A DID might provide the means to return the DID subject itself, if the DID subject is an information resource such as a data model.
This document specifies the DID syntax, a common data model, core properties, serialized representations, DID operations, and an explanation of the process of resolving DIDs to the resources that they represent.
This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.
The W3C Decentralized Identifier Working Group has published this document as a W3C Proposed Recommendation and is requesting that interested parties review this specification by August 26th, 2021.
At the time of publication, there existed 103 experimental DID Method specifications, 32 experimental DID Method driver implementations, a test suite that determines whether or not a given implementation is conformant with this specification and 46 implementations submitted to the conformance test suite. Readers are advised to heed the DID Core issues and DID Core Test Suite issues that each contain the latest list of concerns and proposed changes that might result in alterations to this specification. At the time of publication, no additional substantive issues, changes, or modifications are expected.
Comments regarding this document are welcome. Please file issues directly on GitHub, or send them to public-did-wg@w3.org ( subscribe, archives).
This document was published by the Decentralized Identifier Working Group as a Candidate Recommendation Draft. This document is intended to become a W3C Recommendation.
GitHub Issues are preferred for discussion of this specification. Alternatively, you can send comments to our mailing list. Please send them to public-did-wg@w3.org (subscribe, archives).
Publication as a Candidate Recommendation does not imply endorsement by the W3C Membership. A Candidate Recommendation Draft integrates changes from the previous Candidate Recommendation that the Working Group intends to include in a subsequent Candidate Recommendation Snapshot.
This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.
This document was produced by a group operating under the W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.
This document is governed by the 15 September 2020 W3C Process Document.
This section is non-normative.
As individuals and organizations, many of us use globally unique identifiers in a wide variety of contexts. They serve as communications addresses (telephone numbers, email addresses, usernames on social media), ID numbers (for passports, drivers licenses, tax IDs, health insurance), and product identifiers (serial numbers, barcodes, RFIDs). URIs (Uniform Resource Identifiers) are used for resources on the Web and each web page you view in a browser has a globally unique URL (Uniform Resource Locator).
The vast majority of these globally unique identifiers are not under our control. They are issued by external authorities that decide who or what they refer to and when they can be revoked. They are useful only in certain contexts and recognized only by certain bodies not of our choosing. They might disappear or cease to be valid with the failure of an organization. They might unnecessarily reveal personal information. In many cases, they can be fraudulently replicated and asserted by a malicious third-party, which is more commonly known as "identity theft".
The Decentralized Identifiers (DIDs) defined in this specification are a new type of globally unique identifier. They are designed to enable individuals and organizations to generate their own identifiers using systems they trust. These new identifiers enable entities to prove control over them by authenticating using cryptographic proofs such as digital signatures.
Since the generation and assertion of Decentralized Identifiers is entity-controlled, each entity can have as many DIDs as necessary to maintain their desired separation of identities, personas, and interactions. The use of these identifiers can be scoped appropriately to different contexts. They support interactions with other people, institutions, or systems that require entities to identify themselves, or things they control, while providing control over how much personal or private data should be revealed, all without depending on a central authority to guarantee the continued existence of the identifier. These ideas are explored in the DID Use Cases document [DID-USE-CASES].
This specification does not presuppose any particular technology or cryptography to underpin the generation, persistence, resolution, or interpretation of DIDs. For example, implementers can create Decentralized Identifiers based on identifiers registered in federated or centralized identity management systems. Indeed, almost all types of identifier systems can add support for DIDs. This creates an interoperability bridge between the worlds of centralized, federated, and decentralized identifiers. This also enables implementers to design specific types of DIDs to work with the computing infrastructure they trust, such as distributed ledgers, decentralized file systems, distributed databases, and peer-to-peer networks.
This specification is for:
In addition to this specification, readers might find the Use Cases and Requirements for Decentralized Identifiers [DID-USE-CASES] document useful.
This section is non-normative.
A DID is a simple text string consisting of three parts: 1) the
did
URI scheme identifier, 2) the identifier for the DID
method, and 3) the DID method-specific identifier.
The example DID above resolves to a DID document. A DID document contains information associated with the DID, such as ways to cryptographically authenticate a DID controller.
{
"@context": [
"https://www.w3.org/ns/did/v1",
"https://w3id.org/security/suites/ed25519-2020/v1"
]
"id": "did:example:123456789abcdefghi",
"authentication": [{
// used to authenticate as did:...fghi
"id": "did:example:123456789abcdefghi#keys-1",
"type": "Ed25519VerificationKey2020",
"controller": "did:example:123456789abcdefghi",
"publicKeyMultibase": "zH3C2AVvLMv6gmMNam3uVAjZpfkcJCwDwnZn6z3wXmqPV"
}]
}
This section is non-normative.
Decentralized Identifiers are a component of larger systems, such as the Verifiable Credentials ecosystem [VC-DATA-MODEL], which influenced the design goals for this specification. The design goals for Decentralized Identifiers are summarized here.
Goal | Description |
---|---|
Decentralization | Eliminate the requirement for centralized authorities or single point failure in identifier management, including the registration of globally unique identifiers, public verification keys, services, and other information. |
Control | Give entities, both human and non-human, the power to directly control their digital identifiers without the need to rely on external authorities. |
Privacy | Enable entities to control the privacy of their information, including minimal, selective, and progressive disclosure of attributes or other data. |
Security | Enable sufficient security for requesting parties to depend on DID documents for their required level of assurance. |
Proof-based | Enable DID controllers to provide cryptographic proof when interacting with other entities. |
Discoverability | Make it possible for entities to discover DIDs for other entities, to learn more about or interact with those entities. |
Interoperability | Use interoperable standards so DID infrastructure can make use of existing tools and software libraries designed for interoperability. |
Portability | Be system- and network-independent and enable entities to use their digital identifiers with any system that supports DIDs and DID methods. |
Simplicity | Favor a reduced set of simple features to make the technology easier to understand, implement, and deploy. |
Extensibility | Where possible, enable extensibility provided it does not greatly hinder interoperability, portability, or simplicity. |
This section is non-normative.
This section provides a basic overview of the major components of Decentralized Identifier architecture.
Six internally-labeled shapes appear in the diagram, with labeled arrows between them, as follows. In the center of the diagram is a rectangle labeled DID URL, containing small typewritten text "did:example:123/path/to/rsrc". At the center top of the diagram is a rectangle labeled, "DID", containing small typewritten text "did:example:123". At the top left of the diagram is an oval, labeled "DID Subject". At the bottom center of the diagram is a rectangle labeled, "DID document". At the bottom left is an oval, labeled, "DID Controller". On the center right of the diagram is a two-dimensional rendering of a cylinder, labeled, "Verifiable Data Registry".
From the top of the "DID URL" rectangle, an arrow, labeled "contains", extends upwards, pointing to the "DID" rectangle. From the bottom of the "DID URL" rectangle, an arrow, labeled "refers, and dereferences, to", extends downward, pointing to the "DID document" rectangle. An arrow from the "DID" rectangle, labeled "resolves to", points down to the "DID document" rectangle. An arrow from the "DID" rectangle, labeled "refers to", points left to the "DID subject" oval. An arrow from the "DID controller" oval, labeled "controls", points right to the "DID document" rectangle. An arrow from the "DID" rectangle, labeled "recorded on", points downards to the right, to the "Verifiable Data Registry" cylinder. An arrow from the "DID document" rectangle, labeled "recorded on", points upwards to the right to the "Verifiable Data Registry" cylinder.
did:
, a method identifier, and a unique,
method-specific identifier specified by the DID method. DIDs are
resolvable to DID documents. A DID URL extends the syntax of a
basic DID to incorporate other standard URI components such as
path, query, and fragment in order to locate a particular
resource—for example, a cryptographic public key inside a DID
document, or a resource external to the DID document.
These concepts are elaborated upon in § 3.1 DID Syntax and § 3.2 DID URL Syntax.
As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.
The key words MAY, MUST, MUST NOT, OPTIONAL, RECOMMENDED, REQUIRED, SHOULD, and SHOULD NOT in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.
This document contains examples that contain JSON and JSON-LD content.
Some of these examples contain characters that are invalid, such as inline
comments (//
) and the use of ellipsis (...
) to denote
information that adds little value to the example. Implementers are cautioned to
remove this content if they desire to use the information as valid JSON
or JSON-LD.
Some examples contain terms, both property names and values, that are not
defined in this specification. These are indicated with a comment (//
external (property name|value)
). Such terms, when used in a DID
document, are expected to be registered in the DID Specification Registries
[DID-SPEC-REGISTRIES] with links to both a formal definition and a JSON-LD
context.
Interoperability of implementations for DIDs and DID documents is tested by evaluating an implementation's ability to create and parse DIDs and DID documents that conform to this specification. Interoperability for producers and consumers of DIDs and DID documents is provided by ensuring the DIDs and DID documents conform. Interoperability for DID method specifications is provided by the details in each DID method specification. It is understood that, in the same way that a web browser is not required to implement all known URI schemes, conformant software that works with DIDs is not required to implement all known DID methods. However, all implementations of a given DID method are expected to be interoperable for that method.
A conforming DID is any concrete expression of the rules specified in § 3. Identifier which complies with relevant normative statements in that section.
A conforming DID document is any concrete expression of the data model described in this specification which complies with the relevant normative statements in § 4. Data Model and § 5. Core Properties. A serialization format for the conforming document is deterministic, bi-directional, and lossless, as described in § 6. Representations.
A conforming producer is any algorithm realized as software and/or hardware that generates conforming DIDs or conforming DID Documents and complies with the relevant normative statements in § 6. Representations.
A conforming consumer is any algorithm realized as software and/or hardware that consumes conforming DIDs or conforming DID documents and complies with the relevant normative statements in § 6. Representations.
A conforming DID resolver is any algorithm realized as software and/or hardware that complies with the relevant normative statements in § 7.1 DID Resolution.
A conforming DID URL dereferencer is any algorithm realized as software and/or hardware that complies with the relevant normative statements in § 7.2 DID URL Dereferencing.
A conforming DID method is any specification that complies with the relevant normative statements in § 8. Methods.
This section is non-normative.
This section defines the terms used in this specification and throughout decentralized identifier infrastructure. A link to these terms is included whenever they appear in this specification.
controller
property at the top level of the
DID document. Note that a DID controller might be the DID
subject.
#
). DID fragment syntax is identical to URI fragment syntax.
/
) character and ends with either a question mark
(?
) character, a fragment hash sign (#
) character,
or the end of the DID URL. DID path syntax is identical to URI path syntax.
See § Path.
?
). DID query syntax is identical to URI query
syntax. See § Query.
did:
as defined in § 3.1 DID Syntax. Each DID method specification defines a specific
DID method scheme that works with that specific DID method. In a specific DID
method scheme, the DID method name follows the first colon and terminates with
the second colon, e.g., did:example:
/
character), optional DID query
(with its leading ?
character), and optional DID fragment
(with its leading #
character).
A set of parameters that can be used together with a process to independently verify a proof. For example, a cryptographic public key can be used as a verification method with respect to a digital signature; in such usage, it verifies that the signer possessed the associated cryptographic private key.
"Verification" and "proof" in this definition are intended to apply broadly. For example, a cryptographic public key might be used during Diffie-Hellman key exchange to negotiate a shared symmetric key for encryption. This guarantees the integrity of the key agreement process. It is thus another type of verification method, even though descriptions of the process might not use the words "verification" or "proof."
An expression of the relationship between the DID subject and a verification method. An example of a verification relationship is § 5.3.1 Authentication.
In addition to the terminology above, this specification also uses terminology from the [INFRA] specification to formally define the data model. When [INFRA] terminology is used, such as string, set, and map, it is linked directly to that specification.
This section describes the formal syntax for DIDs and DID URLs. The term "generic" is used to differentiate the syntax defined here from syntax defined by specific DID methods in their respective specifications. The creation processes, and their timing, for DIDs and DID URLs are described in § 8.2 Method Operations and § B.2 Creation of a DID.
The generic DID scheme is a URI scheme conformant with
[RFC3986]. The ABNF definition can be found below, which uses the syntax in
[RFC5234] and the corresponding definitions for ALPHA
and
DIGIT
. All other rule names not defined in the ABNF below are
defined in [RFC3986]. All DIDs MUST conform to the
DID Syntax ABNF Rules.
The DID Syntax ABNF Rules |
---|
did = "did:" method-name ":" method-specific-id method-name = 1*method-char method-char = %x61-7A / DIGIT method-specific-id = *( *idchar ":" ) 1*idchar idchar = ALPHA / DIGIT / "." / "-" / "_" / pct-encoded pct-encoded = "%" HEXDIG HEXDIG |
For requirements on DID methods relating to the DID syntax, see Section § 8.1 Method Syntax.
A DID URL is a network location identifier for a specific resource. It can be used to retrieve things like representations of DID subjects, verification methods, services, specific parts of a DID document, or other resources.
The following is the ABNF definition using the syntax in [RFC5234]. It builds
on the did
scheme defined in § 3.1 DID Syntax. The path-abempty
, query
, and fragment
components are
defined in [RFC3986]. All DID URLs MUST conform to the
DID URL Syntax ABNF Rules. DID methods can further restrict these
rules, as described in § 8.1 Method Syntax.
The DID URL Syntax ABNF Rules |
---|
did-url = did path-abempty [ "?" query ] [ "#" fragment ] |
Although the semicolon (;
) character can be used according to the
rules of the DID URL syntax, future versions of this specification may
use it as a sub-delimiter for parameters as described in [MATRIX-URIS]. To
avoid future conflicts, developers ought to refrain from using it.
A DID path is identical to a generic URI path and conforms to the
path-abempty
ABNF rule in RFC 3986, section 3.3. As with
URIs, path semantics can be specified by DID Methods, which in
turn might enable DID controllers to further specialize those semantics.
did:example:123456/path
A DID query is identical to a generic URI query and conforms to
the query
ABNF rule in RFC 3986, section 3.4. This syntax
feature is elaborated upon in § 3.2.1 DID Parameters.
did:example:123456?versionId=1
DID fragment syntax and semantics are identical to a generic URI
fragment and conforms to the fragment
ABNF rule in RFC 3986, section 3.5.
A DID fragment is used as a method-independent reference into a DID document or external resource. Some examples of DID fragment identifiers are shown below.
did:example:123#public-key-0
did:example:123#agent
did:example:123?service=agent&relativeRef=/credentials#degree
In order to maximize interoperability, implementers are urged to ensure that DID fragments are interpreted in the same way across representations (see § 6. Representations). For example, while JSON Pointer [RFC6901] can be used in a DID fragment, it will not be interpreted in the same way across non-JSON representations.
Additional semantics for fragment identifiers, which are compatible with and layered upon the semantics in this section, are described for JSON-LD representations in § E.2 application/did+ld+json. For information about how to dereference a DID fragment, see § 7.2 DID URL Dereferencing.
The DID URL syntax supports a simple format for parameters based on the
query
component described in § Query. Adding a DID
parameter to a DID URL means that the parameter becomes part of the
identifier for a resource.
did:example:123?versionTime=2021-05-10T17:00:00Z
did:example:123?service=files&relativeRef=/resume.pdf
Some DID parameters are completely independent of of any specific DID method and function the same way for all DIDs. Other DID parameters are not supported by all DID methods. Where optional parameters are supported, they are expected to operate uniformly across the DID methods that do support them. The following table provides common DID parameters that function the same way across all DID methods. Support for all DID Parameters is OPTIONAL.
It is generally expected that DID URL dereferencer implementations will reference [DID-RESOLUTION] for additional implementation details. The scope of this specification only defines the contract of the most common query parameters.
Parameter Name | Description |
---|---|
service
|
Identifies a service from the DID document by service ID. If present, the associated value MUST be an ASCII string. |
relativeRef
|
A relative URI reference according to RFC3986 Section 4.2 that identifies a
resource at a service endpoint, which is selected from a DID
document by using the service parameter.
If present, the associated value MUST be an ASCII string and MUST use percent-encoding for
certain characters as specified in RFC3986
Section 2.1.
|
versionId
|
Identifies a specific version of a DID document to be resolved (the version ID could be sequential, or a UUID, or method-specific). If present, the associated value MUST be an ASCII string. |
versionTime
|
Identifies a certain version timestamp of a DID document to be resolved.
That is, the DID document that was valid for a DID at a certain
time. If present, the associated value
MUST be an ASCII string which is a valid XML
datetime value, as defined in section 3.3.7 of W3C XML Schema Definition Language
(XSD) 1.1 Part 2: Datatypes [XMLSCHEMA11-2]. This datetime value MUST be
normalized to UTC 00:00:00 and without sub-second decimal precision.
For example: 2020-12-20T19:17:47Z .
|
hl
|
A resource hash of the DID document to add integrity protection, as specified in [HASHLINK]. This parameter is non-normative. If present, the associated value MUST be an ASCII string. |
Implementers as well as DID method specification authors might use additional DID parameters that are not listed here. For maximum interoperability, it is RECOMMENDED that DID parameters use the DID Specification Registries mechanism [DID-SPEC-REGISTRIES], to avoid collision with other uses of the same DID parameter with different semantics.
DID parameters might be used if there is a clear use case where the parameter needs to be part of a URL that references a resource with more precision than using the DID alone. It is expected that DID parameters are not used if the same functionality can be expressed by passing input metadata to a DID resolver. Additional considerations for processing these parameters are discussed in [DID-RESOLUTION].
The DID resolution and the DID URL dereferencing functions can be influenced by passing input metadata to a DID resolver that are not part of the DID URL (see § 7.1.1 DID Resolution Options). This is comparable to HTTP, where certain parameters could either be included in an HTTP URL, or alternatively passed as HTTP headers during the dereferencing process. The important distinction is that DID parameters that are part of the DID URL should be used to specify what resource is being identified, whereas input metadata that is not part of the DID URL should be use to control how that resource is resolved or dereferenced.
A relative DID URL is any URL value in a DID document that does
not start with did:<method-name>:<method-specific-id>
. More
specifically, it is any URL value that does not start with the ABNF defined in
§ 3.1 DID Syntax. The URL is expected to reference
a resource in the same DID document. Relative DID URLs MAY
contain relative path components, query parameters, and fragment identifiers.
When resolving a relative DID URL reference, the algorithm specified in
RFC3986 Section 5: Reference Resolution
MUST be used. The base URI value is the DID that is
associated with the DID subject, see § 5.1.1 DID Subject. The
scheme is did
. The authority is a
combination of <method-name>:<method-specific-id>
, and the
path, query, and fragment
values are those defined in § Path, § Query, and § Fragment, respectively.
Relative DID URLs are often used to reference verification methods and services in a DID Document without having to use absolute URLs. DID methods where storage size is a consideration might use relative URLs to reduce the storage size of DID documents.
{ "@context": [ "https://www.w3.org/ns/did/v1", "https://w3id.org/security/suites/ed25519-2020/v1" ] "id": "did:example:123456789abcdefghi", "verificationMethod": [{ "id": "did:example:123456789abcdefghi#key-1", "type": "Ed25519VerificationKey2020", // external (property value) "controller": "did:example:123456789abcdefghi", "publicKeyMultibase": "zH3C2AVvLMv6gmMNam3uVAjZpfkcJCwDwnZn6z3wXmqPV" }, ...], "authentication": [ // a relative DID URL used to reference a verification method above "#key-1" ] }
In the example above, the relative DID URL value will be transformed to
an absolute DID URL value of
did:example:123456789abcdefghi#key-1
.
This specification defines a data model that can be used to express DID documents and DID document data structures, which can then be serialized into multiple concrete representations. This section provides a high-level description of the data model, descriptions of the ways different types of properties are expressed in the data model, and instructions for extending the data model.
A DID document consists of a map of entries, where each entry consists of a key/value pair. The DID document data model contains at least two different classes of entries. The first class of entries is called properties, and is specified in section § 5. Core Properties. The second class is made up of representation-specific entries, and is specified in section § 6. Representations.
All entry keys in the DID document data model are strings. All entry values are expressed using one of the abstract data types in the table below, and each representation specifies the concrete serialization format of each data type.
Data Type | Considerations |
---|---|
map | A finite ordered sequence of key/value pairs, with no key appearing twice as specified in [INFRA]. A map is sometimes referred to as an ordered map in [INFRA]. |
list | A finite ordered sequence of items as specified in [INFRA]. |
set | A finite ordered sequence of items that does not contain the same item twice as specified in [INFRA]. A set is sometimes referred to as an ordered set in [INFRA]. |
datetime |
A date and time value that is capable of losslessly expressing all values
expressible by a dateTime as specified in
[XMLSCHEMA11-2].
|
string | A sequence of code units often used to represent human readable language as specified in [INFRA]. |
integer | A real number without a fractional component as specified in [XMLSCHEMA11-2]. To maximize interoperability, implementers are urged to heed the advice regarding integers in RFC8259, Section 6: Numbers. |
double | A value that is often used to approximate arbitrary real numbers as specified in [XMLSCHEMA11-2]. To maximize interoperability, implementers are urged to heed the advice regarding doubles in RFC8259, Section 6: Numbers. |
boolean | A value that is either true or false as defined in [INFRA]. |
null | A value that is used to indicate the lack of a value as defined in [INFRA]. |
As a result of the data model being defined using terminology from [INFRA], property values which can contain more than one item, such as lists, maps and sets, are explicitly ordered. All list-like value structures in [INFRA] are ordered, whether or not that order is significant. For the purposes of this specification, unless otherwise stated, map and set ordering is not important and implementations are not expected to produce or consume deterministically ordered values.
The data model supports two types of extensibility.
It is always possible for two specific implementations to agree out-of-band to use a mutually understood extension or representation that is not recorded in the DID Specification Registries [DID-SPEC-REGISTRIES]; interoperability between such implementations and the larger ecosystem will be less reliable.
A DID is associated with a DID document. DID documents are expressed using the data model and can be serialized into a representation. The following sections define the properties in a DID document, including whether these properties are required or optional. These properties describe relationships between the DID subject and the value of the property.
The following tables contain informative references for the core properties defined by this specification, with expected values, and whether or not they are required. The property names in the tables are linked to the normative definitions and more detailed descriptions of each property.
The property names id
, type
, and
controller
can be present in maps of different types
with possible differences in constraints.
Property | Required? | Value constraints |
---|---|---|
id |
yes | A string that conforms to the rules in § 3.1 DID Syntax. |
alsoKnownAs |
no | A set of strings that conform to the rules of [RFC3986] for URIs. |
controller |
no | A string or a set of strings that conform to the rules in § 3.1 DID Syntax. |
verificationMethod |
no | A set of Verification Method maps that conform to the rules in § Verification Method properties. |
authentication |
no | A set of either Verification Method maps that conform to the rules in § Verification Method properties) or strings that conform to the rules in § 3.2 DID URL Syntax. |
assertionMethod |
no | |
keyAgreement |
no | |
capabilityInvocation |
no | |
capabilityDelegation |
no | |
service |
no | A set of Service Endpoint maps that conform to the rules in § Service properties. |
Property | Required? | Value constraints |
---|---|---|
id |
yes | A string that conforms to the rules in § 3.2 DID URL Syntax. |
controller |
yes | A string that conforms to the rules in § 3.1 DID Syntax. |
type |
yes | A string. |
publicKeyJwk |
no | A map representing a JSON Web Key that conforms to [RFC7517]. See definition of publicKeyJwk for additional constraints. |
publicKeyMultibase |
no | A string that conforms to a [MULTIBASE] encoded public key. |
Property | Required? | Value constraints |
---|---|---|
id |
yes | A string that conforms to the rules of [RFC3986] for URIs. |
type |
yes | A string or a set of strings. |
serviceEndpoint |
yes | A string that conforms to the rules of [RFC3986] for URIs, a map, or a set composed of a one or more strings that conform to the rules of [RFC3986] for URIs and/or maps. |
This section describes the mechanisms by which DID documents include identifiers for DID subjects and DID controllers.
The DID for a particular DID subject is expressed using the
id
property in the DID document.
id
MUST be a string that conforms to the rules in § 3.1 DID Syntax and MUST exist in the root map of the data
model for the DID document.
{ "id": "did:example:123456789abcdefghijk" }
The id
property only denotes the DID of the
DID subject when it is present in the topmost
map of the DID document.
DID method specifications can create intermediate representations of a
DID document that do not contain the id
property,
such as when a DID resolver is performing DID resolution.
However, the fully resolved DID document always contains a valid
id
property.
A DID controller is an entity that is authorized to make changes to a DID document. The process of authorizing a DID controller is defined by the DID method.
controller
property is OPTIONAL. If present, the value MUST
be a string or a set of strings that conform to the rules in § 3.1 DID Syntax. The corresponding DID document(s) SHOULD
contain verification relationships that explicitly permit the use of
certain verification methods for specific purposes.
When a controller
property is present in a DID
document, its value expresses one or more DIDs. Any verification
methods contained in the DID documents for those DIDs SHOULD
be accepted as authoritative, such that proofs that satisfy those
verification methods are to be considered equivalent to proofs provided
by the DID subject.
{ "@context": "https://www.w3.org/ns/did/v1", "id": "did:example:123456789abcdefghi", "controller": "did:example:bcehfew7h32f32h7af3", }
Note that authorization provided by the value of controller
is
separate from authentication as described in § 5.3.1 Authentication.
This is particularly important for key recovery in the case of cryptographic key
loss, where the DID subject no longer has access to their keys, or key
compromise, where the DID controller's trusted third parties need to
override malicious activity by an attacker. See § 9. Security Considerations for information related to threat models
and attack vectors.
A DID subject can have multiple identifiers for different purposes, or
at different times. The assertion that two or more DIDs (or other types
of URI) refer to the same DID subject can be made using the
alsoKnownAs
property.
alsoKnownAs
property is OPTIONAL. If present, the value MUST
be a set where each item in the
set is a URI conforming to [RFC3986].
Applications might choose to consider two identifiers related by
alsoKnownAs
to be equivalent if the
alsoKnownAs
relationship is reciprocated in the reverse
direction. It is best practice not to consider them equivalent in the
absence of this inverse relationship. In other words, the presence of an
alsoKnownAs
assertion does not prove that this assertion
is true. Therefore, it is strongly advised that a requesting party obtain
independent verification of an alsoKnownAs
assertion.
Given that the DID subject might use different identifiers for different purposes, an expectation of strong equivalence between the two identifiers, or merging the information of the two corresponding DID documents, is not necessarily appropriate, even with a reciprocal relationship.
A DID document can express verification methods, such as cryptographic public keys, which can be used to authenticate or authorize interactions with the DID subject or associated parties. For example, a cryptographic public key can be used as a verification method with respect to a digital signature; in such usage, it verifies that the signer could use the associated cryptographic private key. Verification methods might take many parameters. An example of this is a set of five cryptographic keys from which any three are required to contribute to a cryptographic threshold signature.
The verificationMethod
property is OPTIONAL. If present, the value
MUST be a set of verification
methods, where each verification method is expressed using a map. The verification method map MUST include the id
,
type
, controller
, and specific verification material
properties that are determined by the value of type
and are defined
in § 5.2.1 Verification Material. A verification method MAY
include additional properties. Verification methods SHOULD be registered
in the DID Specification Registries [DID-SPEC-REGISTRIES].
The value of the id
property for a verification
method MUST be a string that conforms to the
rules in Section § 3.2 DID URL Syntax.
type
property MUST be a string that references exactly one verification
method type. In order to maximize global interoperability, the
verification method type SHOULD be registered in the DID Specification
Registries [DID-SPEC-REGISTRIES].
controller
property MUST be a string that conforms to the rules in § 3.1 DID Syntax.
{
"@context": [
"https://www.w3.org/ns/did/v1",
"https://w3id.org/security/suites/jws-2020/v1"
"https://w3id.org/security/suites/ed25519-2020/v1"
]
"id": "did:example:123456789abcdefghi",
...
"verificationMethod": [{
"id": ...,
"type": ...,
"controller": ...,
"publicKeyJwk": ...
}, {
"id": ...,
"type": ...,
"controller": ...,
"publicKeyMultibase": ...
}]
}
The semantics of the controller
property are the same when the
subject of the relationship is the DID document as when the subject of
the relationship is a verification method, such as a cryptographic public
key. Since a key can't control itself, and the key controller cannot be inferred
from the DID document, it is necessary to explicitly express the identity
of the controller of the key. The difference is that the value of
controller
for a verification method is not
necessarily a DID controller. DID controllers are expressed
using the controller
property at the highest level of the
DID document (the topmost map in the
data model); see § 5.1.2 DID Controller.
Verification material is any information that is used by a process that applies
a verification method. The type
of a verification
method is expected to be used to determine its compatibility with such
processes. Examples of verification material properties are
publicKeyJwk
or publicKeyMultibase
. A
cryptographic suite specification is responsible for specifying the
verification method type
and its associated verification
material. For example, see
JSON
Web Signature 2020 and Ed25519 Signature 2020.
For all registered verification method types and associated verification
material available for DIDs, please see the DID Specification Registries
[DID-SPEC-REGISTRIES].
To increase the likelihood of interoperable implementations, this specification limits the number of formats for expressing verification material in a DID document. The fewer formats that implementers have to implement, the more likely it will be that they will support all of them. This approach attempts to strike a delicate balance between ease of implementation and supporting formats that have historically had broad deployment. Two supported verification material properties are listed below:
The publicKeyJwk
property is OPTIONAL. If present, the value MUST
be a map representing a JSON Web Key that
conforms to [RFC7517]. The map MUST NOT
contain "d", or any other members of the private information class as described
in Registration
Template. It is RECOMMENDED that verification methods that use JWKs
[RFC7517] to represent their public keys use the value of kid
as
their fragment identifier. It is RECOMMENDED that JWK
kid
values are set to the public key fingerprint [RFC7638]. See
the first key in Example 13 for
an example of a public key with a compound key identifier.
The publicKeyMultibase
property is OPTIONAL. This feature is
non-normative. If present, the value MUST be a string representation of a [MULTIBASE] encoded
public key.
Note that the [MULTIBASE] specification is not yet a standard and is
subject to change. There might be some use cases for this data format
where publicKeyMultibase
is defined, to allow for
expression of public keys, but privateKeyMultibase
is not defined, to protect against accidental leakage of secret keys.
A verification method MUST NOT contain multiple verification material
properties for the same material. For example, expressing key material in a
verification method using both publicKeyJwk
and
publicKeyMultibase
at the same time is prohibited.
An example of a DID document containing verification methods using both properties above is shown below.
{ "@context": [ "https://www.w3.org/ns/did/v1", "https://w3id.org/security/suites/jws-2020/v1", "https://w3id.org/security/suites/ed25519-2020/v1" ] "id": "did:example:123456789abcdefghi", ... "verificationMethod": [{ "id": "did:example:123#_Qq0UL2Fq651Q0Fjd6TvnYE-faHiOpRlPVQcY_-tA4A", "type": "JsonWebKey2020", // external (property value) "controller": "did:example:123", "publicKeyJwk": { "crv": "Ed25519", // external (property name) "x": "VCpo2LMLhn6iWku8MKvSLg2ZAoC-nlOyPVQaO3FxVeQ", // external (property name) "kty": "OKP", // external (property name) "kid": "_Qq0UL2Fq651Q0Fjd6TvnYE-faHiOpRlPVQcY_-tA4A" // external (property name) } }, { "id": "did:example:123456789abcdefghi#keys-1", "type": "Ed25519VerificationKey2020", // external (property value) "controller": "did:example:pqrstuvwxyz0987654321", "publicKeyMultibase": "zH3C2AVvLMv6gmMNam3uVAjZpfkcJCwDwnZn6z3wXmqPV" }], ... }
Verification methods can be embedded in or referenced from properties associated with various verification relationships as described in § 5.3 Verification Relationships. Referencing verification methods allows them to be used by more than one verification relationship.
If the value of a verification method property is a map, the verification method has been
embedded and its properties can be accessed directly. However, if the value is a
URL string, the verification method has
been included by reference and its properties will need to be retrieved from
elsewhere in the DID document or from another DID document. This
is done by dereferencing the URL and searching the resulting resource for a
verification method map with an
id
property whose value matches the URL.
{ ... "authentication": [ // this key is referenced and might be used by // more than one verification relationship "did:example:123456789abcdefghi#keys-1", // this key is embedded and may *only* be used for authentication { "id": "did:example:123456789abcdefghi#keys-2", "type": "Ed25519VerificationKey2020", // external (property value) "controller": "did:example:123456789abcdefghi", "publicKeyMultibase": "zH3C2AVvLMv6gmMNam3uVAjZpfkcJCwDwnZn6z3wXmqPV" } ], ... }
A verification relationship expresses the relationship between the DID subject and a verification method.
Different verification relationships enable the associated verification methods to be used for different purposes. It is up to a verifier to ascertain the validity of a verification attempt by checking that the verification method used is contained in the appropriate verification relationship property of the DID Document.
The verification relationship between the DID subject and the
verification method is explicit in the DID document.
Verification methods that are not associated with a particular
verification relationship cannot be used for that verification
relationship. For example, a verification method in the value of
the authentication
property cannot be used to engage in
key agreement protocols with the DID subject—the value of the
keyAgreement
property needs to be used for that.
The DID document does not express revoked keys using a verification relationship. If a referenced verification method is not in the latest DID Document used to dereference it, then that verification method is considered invalid or revoked. Each DID method specification is expected to detail how revocation is performed and tracked.
The following sections define several useful verification relationships. A DID document MAY include any of these, or other properties, to express a specific verification relationship. In order to maximize global interoperability, any such properties used SHOULD be registered in the DID Specification Registries [DID-SPEC-REGISTRIES].
The authentication
verification relationship is used to
specify how the DID subject is expected to be authenticated, for
purposes such as logging into a website or engaging in any sort of
challenge-response protocol.
authentication
property is OPTIONAL. If present, the associated
value MUST be a set of one or more
verification methods. Each verification method MAY be embedded or
referenced.
{ "@context": [ "https://www.w3.org/ns/did/v1", "https://w3id.org/security/suites/ed25519-2020/v1" ], "id": "did:example:123456789abcdefghi", ... "authentication": [ // this method can be used to authenticate as did:...fghi "did:example:123456789abcdefghi#keys-1", // this method is *only* approved for authentication, it may not // be used for any other proof purpose, so its full description is // embedded here rather than using only a reference { "id": "did:example:123456789abcdefghi#keys-2", "type": "Ed25519VerificationKey2020", "controller": "did:example:123456789abcdefghi", "publicKeyMultibase": "zH3C2AVvLMv6gmMNam3uVAjZpfkcJCwDwnZn6z3wXmqPV" } ], ... }
If authentication is established, it is up to the DID method or other application to decide what to do with that information. A particular DID method could decide that authenticating as a DID controller is sufficient to, for example, update or delete the DID document. Another DID method could require different keys, or a different verification method entirely, to be presented in order to update or delete the DID document than that used to authenticate. In other words, what is done after the authentication check is out of scope for the data model; DID methods and applications are expected to define this themselves.
This is useful to any authentication verifier that needs to check to
see if an entity that is attempting to authenticate is, in fact,
presenting a valid proof of authentication. When a verifier receives
some data (in some protocol-specific format) that contains a proof that was made
for the purpose of "authentication", and that says that an entity is identified
by the DID, then that verifier checks to ensure that the proof
can be verified using a verification method (e.g., public key) listed
under authentication
in the DID Document.
Note that the verification method indicated by the
authentication
property of a DID document can only be
used to authenticate the DID subject. To authenticate a
different DID controller, the entity associated with the value of
controller
, as defined in § 5.1.2 DID Controller, needs to
authenticate with its own DID document and associated
authentication
verification relationship.
The assertionMethod
verification relationship is used to
specify how the DID subject is expected to express claims, such as for
the purposes of issuing a Verifiable Credential [VC-DATA-MODEL].
assertionMethod
property is OPTIONAL. If present, the
associated value MUST be a set of
one or more verification methods. Each verification method MAY be
embedded or referenced.
This property is useful, for example, during the processing of a verifiable
credential by a verifier. During verification, a verifier checks to see if a
verifiable credential contains a proof created by the DID subject
by checking that the verification method used to assert the proof is
associated with the assertionMethod
property in the
corresponding DID document.
{ "@context": [ "https://www.w3.org/ns/did/v1", "https://w3id.org/security/suites/ed25519-2020/v1" ], "id": "did:example:123456789abcdefghi", ... "assertionMethod": [ // this method can be used to assert statements as did:...fghi "did:example:123456789abcdefghi#keys-1", // this method is *only* approved for assertion of statements, it is not // used for any other verification relationship, so its full description is // embedded here rather than using a reference { "id": "did:example:123456789abcdefghi#keys-2", "type": "Ed25519VerificationKey2020", // external (property value) "controller": "did:example:123456789abcdefghi", "publicKeyMultibase": "zH3C2AVvLMv6gmMNam3uVAjZpfkcJCwDwnZn6z3wXmqPV" } ], ... }
The keyAgreement
verification relationship is used to
specify how an entity can generate encryption material in order to transmit
confidential information intended for the DID subject, such as for
the purposes of establishing a secure communication channel with the recipient.
keyAgreement
property is OPTIONAL. If present, the associated
value MUST be a set of one or more
verification methods. Each verification method MAY be embedded or
referenced.
An example of when this property is useful is when encrypting a message intended for the DID subject. In this case, the counterparty uses the cryptographic public key information in the verification method to wrap a decryption key for the recipient.
{ "@context": "https://www.w3.org/ns/did/v1", "id": "did:example:123456789abcdefghi", ... "keyAgreement": [ // this method can be used to perform key agreement as did:...fghi "did:example:123456789abcdefghi#keys-1", // this method is *only* approved for key agreement usage, it will not // be used for any other verification relationship, so its full description is // embedded here rather than using only a reference { "id": "did:example:123#zC9ByQ8aJs8vrNXyDhPHHNNMSHPcaSgNpjjsBYpMMjsTdS", "type": "X25519KeyAgreementKey2019", // external (property value) "controller": "did:example:123", "publicKeyMultibase": "z9hFgmPVfmBZwRvFEyniQDBkz9LmV7gDEqytWyGZLmDXE" } ], ... }
The capabilityInvocation
verification relationship is used
to specify a verification method that might be used by the DID
subject to invoke a cryptographic capability, such as the authorization to
update the DID Document.
capabilityInvocation
property is OPTIONAL. If present, the
associated value MUST be a set of
one or more verification methods. Each verification method MAY be
embedded or referenced.
An example of when this property is useful is when a DID subject needs to access a protected HTTP API that requires authorization in order to use it. In order to authorize when using the HTTP API, the DID subject uses a capability that is associated with a particular URL that is exposed via the HTTP API. The invocation of the capability could be expressed in a number of ways, e.g., as a digitally signed message that is placed into the HTTP Headers.
The server providing the HTTP API is the verifier of the capability and
it would need to verify that the verification method referred to by the
invoked capability exists in the capabilityInvocation
property of the DID document. The verifier would also check to make sure
that the action being performed is valid and the capability is appropriate for
the resource being accessed. If the verification is successful, the server has
cryptographically determined that the invoker is authorized to access the
protected resource.
{ "@context": [ "https://www.w3.org/ns/did/v1", "https://w3id.org/security/suites/ed25519-2020/v1" ], "id": "did:example:123456789abcdefghi", ... "capabilityInvocation": [ // this method can be used to invoke capabilities as did:...fghi "did:example:123456789abcdefghi#keys-1", // this method is *only* approved for capability invocation usage, it will not // be used for any other verification relationship, so its full description is // embedded here rather than using only a reference { "id": "did:example:123456789abcdefghi#keys-2", "type": "Ed25519VerificationKey2020", // external (property value) "controller": "did:example:123456789abcdefghi", "publicKeyMultibase": "zH3C2AVvLMv6gmMNam3uVAjZpfkcJCwDwnZn6z3wXmqPV" } ], ... }
The capabilityDelegation
verification relationship is used
to specify a mechanism that might be used by the DID subject to delegate
a cryptographic capability to another party, such as delegating the authority
to access a specific HTTP API to a subordinate.
capabilityDelegation
property is OPTIONAL. If present, the
associated value MUST be a set of
one or more verification methods. Each verification method MAY be
embedded or referenced.
An example of when this property is useful is when a DID controller
chooses to delegate their capability to access a protected HTTP API to a party
other than themselves. In order to delegate the capability, the DID
subject would use a verification method associated with the
capabilityDelegation
verification relationship to
cryptographically sign the capability over to another DID subject. The
delegate would then use the capability in a manner that is similar to the
example described in § 5.3.4 Capability Invocation.
{ "@context": [ "https://www.w3.org/ns/did/v1", "https://w3id.org/security/suites/ed25519-2020/v1" ], "id": "did:example:123456789abcdefghi", ... "capabilityDelegation": [ // this method can be used to perform capability delegation as did:...fghi "did:example:123456789abcdefghi#keys-1", // this method is *only* approved for granting capabilities; it will not // be used for any other verification relationship, so its full description is // embedded here rather than using only a reference { "id": "did:example:123456789abcdefghi#keys-2", "type": "Ed25519VerificationKey2020", // external (property value) "controller": "did:example:123456789abcdefghi", "publicKeyMultibase": "zH3C2AVvLMv6gmMNam3uVAjZpfkcJCwDwnZn6z3wXmqPV" } ], ... }
Services are used in DID documents to express ways of communicating with the DID subject or associated entities. A service can be any type of service the DID subject wants to advertise, including decentralized identity management services for further discovery, authentication, authorization, or interaction.
Due to privacy concerns, revealing public information through services, such as social media accounts, personal websites, and email addresses, is discouraged. Further exploration of privacy concerns can be found in § 10.1 Keep Personal Data Private and § 10.6 Service Privacy. The information associated with services is often service specific. For example, the information associated with an encrypted messaging service can express how to initiate the encrypted link before messaging begins.
Services are expressed using the service
property,
which is described below:
The service
property is OPTIONAL. If present, the associated value
MUST be a set of services,
where each service is described by a map.
Each service map MUST contain
id
, type
, and
serviceEndpoint
properties. Each service extension MAY
include additional properties and MAY further restrict the properties associated
with the extension.
id
property MUST be a URI conforming to
[RFC3986]. A conforming producer MUST NOT produce
multiple service
entries with the same id
.
A conforming consumer MUST produce an error if it detects
multiple service
entries with the same id
.
type
property MUST be a string or a set of strings. In order to maximize interoperability,
the service type and its associated properties SHOULD be
registered in the DID Specification Registries [DID-SPEC-REGISTRIES].
serviceEndpoint
property MUST be a string, a map, or
a set composed of one or more strings and/or maps. All string
values MUST be valid URIs conforming to [RFC3986] and normalized
according to the Normalization and Comparison
rules in RFC3986 and to any normalization rules in its applicable URI
scheme specification.
For more information regarding privacy and security considerations related to services see § 10.6 Service Privacy, § 10.1 Keep Personal Data Private, § 10.3 DID Document Correlation Risks, and § 9.3 Authentication Service Endpoints.
{
"service": [{
"id":"did:example:123#linked-domain",
"type": "LinkedDomains", // external (property value)
"serviceEndpoint": "https://bar.example.com"
}]
}
A concrete serialization of a DID document in this specification is called a representation. A representation is created by serializing the data model through a process called production. A representation is transformed into the data model through a process called consumption. The production and consumption processes enable the conversion of information from one representation to another. This specification defines representations for JSON and JSON-LD, and developers can use any other representation, such as XML or YAML, that is capable of expressing the data model. The following sections define the general rules for production and consumption, as well as the JSON and JSON-LD representations.
In addition to the representations defined in this specification, implementers can use other representations, providing each such representation is properly specified (including rules for interoperable handling of properties not listed in the DID Specification Registries [DID-SPEC-REGISTRIES]). See § 4.1 Extensibility for more information.
The requirements for all representations are as follows:
dateTime
lexical serialization to represent
datetimes. A representation MAY choose to serialize the data model data types using a different lexical
serializations as long as the consumption process back into the data model is lossless. For example, some CBOR-based
representations express datetime values using integers to
represent the number of seconds since the Unix epoch.
The requirements for all conforming producers are as follows:
The requirements for all conforming consumers are as follows:
The upper left quadrant of the diagram contains a rectangle with dashed grey outline, containing two blue-outlined rectangles, one above the other. The upper, larger rectangle is labeled, in blue, "Core Properties", and contains the following INFRA notation:
«[
"id" → "example:123",
"verificationMethod" → « «[
"id": "did:example:123#keys-1",
"controller": "did:example:123",
"type": "Ed25519VerificationKey2018",
"publicKeyBase58": "H3C2AVvLMv6gmMNam3uVA"
]» »,
"authentication" → «
"did:example:123#keys-1"
»
]»
The lower, smaller rectangle is labeled, in blue, "Core Representation-specific
Entries (JSON-LD)", and contains the following monospaced INFRA notation:
«[ "@context" → "https://www.w3.org/ns/did/v1" ]»
From the grey-outlined rectangle, three pairs of arrows extend to three different black-outlined rectangles, one on the upper right of the diagram, one in the lower right, and one in the lower left. Each pair of arrows consists of one blue arrow pointing from the grey-outlined rectangle to the respective black-outlined rectangle, labeled "produce", and one red arrow pointing in the reverse direction, labeled "consume". The black-outlined rectangle in the upper right is labeled "application/did+cbor", and contains hexadecimal data. The rectangle in the lower right is labeled "application/did+json", and contains the following JSON data:
{
"id": "did:example:123",
"verificationMethod": [{
"id": "did:example:123#keys-1",
"controller": "did:example:123",
"type": "Ed25519VerificationKey2018",
"publicKeyBase58": "H3C2AVvLMv6gmMNam3uVA"
}],
"authentication": [
"did:example:123#keys-1"
]
}
The rectangle in the lower left is labeled "application/did+ld+json", and contains the following JSON-LD data:
{
"@context": ["https://www.w3.org/ns/did/v1"],
"id": "did:example:123",
"verificationMethod": [{
"id": "did:example:123#keys-1",
"controller": "did:example:123",
"type": "Ed25519VerificationKey2018",
"publicKeyBase58": "H3C2AVvLMv6gmMNam3uVA"
}],
"authentication": [
"did:example:123#keys-1"
]
}
An implementation is expected to convert between representations by using the consumption rules on the source representation resulting in the data model and then using the production rules to serialize data model to the target representation, or any other mechanism that results in the same target representation.
This section defines the production and consumption rules for the JSON representation.
The DID document, DID document data structures, and representation-specific entries map MUST be serialized to the JSON representation according to the following production rules:
Data Type | JSON Representation Type |
---|---|
map | A JSON Object, where each entry is serialized as a member of the JSON Object with the entry key as a JSON String member name and the entry value according to its type, as defined in this table. |
list | A JSON Array, where each element of the list is serialized, in order, as a value of the array according to its type, as defined in this table. |
set | A JSON Array, where each element of the set is added, in order, as a value of the array according to its type, as defined in this table. |
datetime |
A JSON String serialized as an
XML Datetime normalized to
UTC 00:00:00 and without sub-second decimal precision. For example:
2020-12-20T19:17:47Z .
|
string | A JSON String. |
integer | A JSON Number without a decimal or fractional component. |
double | A JSON Number with a decimal and fractional component. |
boolean | A JSON Boolean. |
null | A JSON null literal. |
All implementers creating conforming producers that produce JSON representations are advised to ensure that their algorithms are aligned with the JSON serialization rules in the [INFRA] specification and the precision advisements regarding Numbers in the JSON [RFC8259] specification.
All entries of a DID document MUST be included in the root JSON Object. Entries MAY contain additional
data substructures subject to the value representation rules in the list above.
When serializing a DID document, a conforming producer MUST
specify a media type of application/did+json
to downstream
applications such as described in § 7.1.2 DID Resolution Metadata.
{ "id": "did:example:123456789abcdefghi", "authentication": [{ "id": "did:example:123456789abcdefghi#keys-1", "type": "Ed25519VerificationKey2018", "controller": "did:example:123456789abcdefghi", "publicKeyBase58": "H3C2AVvLMv6gmMNam3uVAjZpfkcJCwDwnZn6z3wXmqPV" }] }
The DID document and DID document data structures JSON representation MUST be deserialized into the data model according to the following consumption rules:
JSON Representation Type | Data Type |
---|---|
JSON Object | A map, where each member of the JSON Object is added as an entry to the map. Each entry key is set as the JSON Object member name. Each entry value is set by converting the JSON Object member value according to the JSON representation type as defined in this table. Since order is not specified by JSON Objects, no insertion order is guaranteed. |
JSON Array where the data model entry value is a list or unknown | A list, where each value of the JSON Array is added to the list in order, converted based on the JSON representation type of the array value, as defined in this table. |
JSON Array where the data model entry value is a set | A set, where each value of the JSON Array is added to the set in order, converted based on the JSON representation type of the array value, as defined in this table. |
JSON String where data model entry value is a datetime | A datetime. |
JSON String, where the data model entry value type is string or unknown | A string. |
JSON Number without a decimal or fractional component | An integer. |
JSON Number with a decimal and fractional component, or when entry value is a double regardless of inclusion of fractional component | A double. |
JSON Boolean | A boolean. |
JSON null literal | A null value. |
All implementers creating conforming consumers that produce JSON representations are advised to ensure that their algorithms are aligned with the JSON conversion rules in the [INFRA] specification and the precision advisements regarding Numbers in the JSON [RFC8259] specification.
If media type information is available to a conforming consumer and the
media type value is application/did+json
, then the data structure
being consumed is a DID document, and the root element MUST be a JSON Object where all members of the object
are entries of the DID document. A conforming consumer for a JSON
representation that is consuming a DID document with a root
element that is not a JSON Object MUST
report an error.
JSON-LD [JSON-LD11] is a JSON-based format used to serialize Linked Data. This section defines the production and consumption rules for the JSON-LD representation.
The JSON-LD representation defines the following representation-specific entries:
The DID document, DID document data structures, and representation-specific entries map MUST be serialized to the JSON-LD representation according to the JSON representation production rules as defined in § 6.2 JSON.
In addition to using the JSON representation production rules,
JSON-LD production MUST include the representation-specific
@context
entry. The serialized value of
@context
MUST be the JSON
String https://www.w3.org/ns/did/v1
, or a JSON Array where the first item is the JSON String
https://www.w3.org/ns/did/v1
and the subsequent items are
serialized according to the JSON representation production
rules.
{
"@context": "https://www.w3.org/ns/did/v1",
...
}
{
"@context": [
"https://www.w3.org/ns/did/v1",
"https://did-method-extension.example/v1"
],
...
}
All implementers creating conforming producers that produce JSON-LD representations are advised to ensure that their algorithms produce valid JSON-LD [JSON-LD11] documents. Invalid JSON-LD documents will cause JSON-LD processors to halt and report errors.
In order to achieve interoperability across different representations, all JSON-LD Contexts and their terms SHOULD be registered in the DID Specification Registries [DID-SPEC-REGISTRIES].
A conforming producer that generates a JSON-LD representation
SHOULD NOT produce a DID document that contains terms not defined via the
@context
as conforming consumers are expected to remove
unknown terms. When serializing a JSON-LD representation of a DID
document, a conforming producer MUST specify a media type of
application/did+ld+json
to downstream applications such as
described in § 7.1.2 DID Resolution Metadata.
The DID document and any DID document data structures expressed by a JSON-LD representation MUST be deserialized into the data model according to the JSON representation consumption rules as defined in § 6.2 JSON.
All implementers creating conforming consumers that consume JSON-LD representations are advised to ensure that their algorithms only accept valid JSON-LD [JSON-LD11] documents. Invalid JSON-LD documents will cause JSON-LD processors to halt and report errors.
Conforming consumers that process a JSON-LD representation SHOULD
drop all terms from a DID document that are not defined via the
@context
.
This section defines the inputs and outputs of DID resolution and DID URL dereferencing. Their exact implementation is out of scope for this specification, but some considerations for implementers are discussed in [DID-RESOLUTION].
All conformant DID resolvers MUST implement the DID resolution functions for at least one DID method and MUST be able to return a DID document in at least one conformant representation.
The DID resolution functions resolve a DID into a DID document by using the "Read" operation of the applicable DID method as described in § 8.2 Method Operations. The details of how this process is accomplished are outside the scope of this specification, but all conforming DID resolvers implement the functions below, which have the following abstract forms:
resolve(did, resolutionOptions) →
« didResolutionMetadata, didDocument, didDocumentMetadata »
resolveRepresentation(did, resolutionOptions) →
« didResolutionMetadata, didDocumentStream, didDocumentMetadata »
The resolve
function returns the DID document in its
abstract form (a map). The
resolveRepresentation
function returns a byte stream of the DID
Document formatted in the corresponding representation.
The upper middle part of the diagram contains a rectangle with dashed grey outline, containing two blue-outlined rectangles, one above the other. The upper, larger rectangle is labeled, in blue, "Core Properties", and contains the following INFRA notation:
«[
"id" → "example:123",
"verificationMethod" → « «[
"id": "did:example:123#keys-1",
"controller": "did:example:123",
"type": "Ed25519VerificationKey2018",
"publicKeyBase58": "H3C2AVvLMv6gmMNam3uVA"
]» »,
"authentication" → «
"did:example:123#keys-1"
»
]»
The lower, smaller rectangle is labeled, in blue, "Core Representation-specific Entries (JSON-LD)", and contains the following monospaced INFRA notation:
«[ "@context" → "https://www.w3.org/ns/did/v1" ]»
From the grey-outlined rectangle, three pairs of arrows extend to three different black-outlined rectangles, aligned in a horizontal row side-by-side, in the bottom half of the diagram. Each pair of arrows consists of one blue arrow pointing from the grey-outlined rectangle to the respective black-outlined rectangle, labeled "produce", and one red arrow pointing in the reverse direction, labeled "consume". The first black-outlined rectangle in the row is labeled "application/did+ld+json", and contains the following JSON-LD data:
{
"@context": ["https://www.w3.org/ns/did/v1"],
"id": "did:example:123",
"verificationMethod": [{
"id": "did:example:123#keys-1",
"controller": "did:example:123",
"type": "Ed25519VerificationKey2018",
"publicKeyBase58": "H3C2AVvLMv6gmMNam3uVA"
}],
"authentication": [
"did:example:123#keys-1"
]
}
The second rectangle in the row is labeled "application/did+json" and contains the following JSON data:
{
"id": "did:example:123",
"verificationMethod": [{
"id": "did:example:123#keys-1",
"controller": "did:example:123",
"type": "Ed25519VerificationKey2018",
"publicKeyBase58": "H3C2AVvLMv6gmMNam3uVA"
}],
"authentication": [
"did:example:123#keys-1"
]
}
The third rectangle in the row is labeled "application/did+cbor", and contains hexadecimal data.
In the left part of the diagram, in the middle, there is a box, with black outline and light gray background. This box is labeled "VERIFIABLE DATA REGISTRY" and contains a symbol representing a graph with nodes and arcs. From this box, one arrow, labeled "resolve()", extends upwards and points to the top half of the diagram where the grey-outlined rectangle is located. Another arrow, labeled "resolveRepresentation()", extends downwards and points to the bottom half of the diagram, where the row of three black-outlined rectangles is located.
The input variables
of the resolve
and resolveRepresentation
functions are
as follows:
These functions each return multiple values, and no limitations
are placed on how these values are returned together.
The return values of resolve
are
didResolutionMetadata, didDocument, and
didDocumentMetadata. The return values of
resolveRepresentation
are
didResolutionMetadata, didDocumentStream, and
didDocumentMetadata. These values are described below:
resolve
and
resolveRepresentation
functions, as it represents data about the
resolution process itself. This structure is REQUIRED, and in the case of an
error in the resolution process, this MUST NOT be empty. This metadata is
defined by § 7.1.2 DID Resolution Metadata. If
resolveRepresentation
was called, this structure MUST contain a
contentType
property containing the Media Type of the
representation found in the didDocumentStream
. If the resolution is
not successful, this structure MUST contain an error
property
describing the error.
resolve
function was
called, this MUST be a DID document abstract data model (a map) as described in § 4. Data Model that
is capable of being transformed into a conforming DID Document
(representation), using the production rules specified by the representation.
The value of id
in the resolved DID document MUST
match the DID that was resolved. If the resolution is unsuccessful, this
value MUST be empty.
resolveRepresentation
function was called, this MUST be a byte stream of the resolved DID
document in one of the conformant
representations. The byte stream might then be
parsed by the caller of the resolveRepresentation
function into a
data model, which can in turn be validated and
processed. If the resolution is unsuccessful, this value MUST be an empty
stream.
didDocument
property. This metadata typically does not change between invocations of the
resolve
and resolveRepresentation
functions unless the
DID document changes, as it represents metadata about the DID
document. If the resolution is unsuccessful, this output MUST be an empty metadata structure. Properties defined by this
specification are in § 7.1.3 DID Document Metadata.
Conforming DID resolver implementations do not alter the signature of
these functions in any way. DID resolver implementations might map the
resolve
and resolveRepresentation
functions to a
method-specific internal function to perform the actual DID resolution
process. DID resolver implementations might implement and expose
additional functions with different signatures in addition to the
resolve
and resolveRepresentation
functions specified
here.
The possible properties within this structure and their possible values are registered in the DID Specification Registries [DID-SPEC-REGISTRIES]. This specification defines the following common properties.
didDocumentStream
if such a representation is supported and
available. This property is OPTIONAL for the resolveRepresentation
function and MUST NOT be used with the resolve
function.
The possible properties within this structure and their possible values are registered in the DID Specification Registries [DID-SPEC-REGISTRIES]. This specification defines the following DID resolution metadata properties:
didDocumentStream
. This property is
REQUIRED if resolution is successful and if the
resolveRepresentation
function was called.
This property MUST NOT
be present if the resolve
function was called. The value of this
property MUST be an ASCII string that is the Media
Type of the conformant representations. The
caller of the resolveRepresentation
function MUST use this value
when determining how to parse and process the didDocumentStream
returned by this function into the data model.
accept
input metadata property is not supported by the DID
method and/or DID resolver implementation.
The possible properties within this structure and their possible values SHOULD be registered in the DID Specification Registries [DID-SPEC-REGISTRIES]. This specification defines the following common properties.
created
property to
indicate the timestamp of the Create operation.
The value of the property MUST be a string
formatted as an XML Datetime
normalized to UTC 00:00:00 and without sub-second decimal precision. For
example: 2020-12-20T19:17:47Z
.
updated
property to
indicate the timestamp of the last Update
operation for the document version which was resolved. The value of the
property MUST follow the same formatting rules as the created
property. The updated
property is omitted if an Update operation
has never been performed on the DID document. If an updated
property exists, it can be the same value as the created
property
when the difference between the two timestamps is less than one second.
true
. If a DID has not been deactivated, this property is OPTIONAL,
but if included, MUST have the boolean value false
.
nextUpdate
property if
the resolved document version is not the latest version of the document. It
indicates the timestamp of the next Update
operation. The value of the property MUST follow the same formatting rules
as the created
property.
versionId
property to
indicate the version of the last Update
operation for the document version which was resolved. The value of the
property MUST be an ASCII string.
nextVersionId
property
if the resolved document version is not the latest version of the document. It
indicates the version of the next Update
operation. The value of the property MUST be an ASCII string.
A DID method can define different forms of a DID that are
logically equivalent. An example is when a DID takes one form prior to
registration in a verifiable data registry and another form after such
registration. In this case, the DID method specification might need to
express one or more DIDs that are logically equivalent to the resolved
DID as a property of the DID document. This is the purpose of the
equivalentId
property.
DID document metadata MAY include an equivalentId
property.
If present, the value MUST be a set where each item is a
string that conforms to the rules in Section § 3.1 DID Syntax. The relationship is a statement that each
equivalentId
value is logically equivalent to the
id
property value and thus refers to the same DID subject.
Each equivalentId
DID value MUST be produced by, and a form
of, the same DID method as the id
property value. (e.g.,
did:example:abc
== did:example:ABC
)
A conforming DID method specification MUST guarantee that each
equivalentId
value is logically equivalent to the
id
property value.
A requesting party is expected to retain the values from the id
and
equivalentId
properties to ensure any subsequent
interactions with any of the values they contain are correctly handled as
logically equivalent (e.g., retain all variants in a database so an interaction
with any one maps to the same underlying account).
equivalentId
is a much stronger form of equivalence than
alsoKnownAs
because the equivalence MUST be guaranteed by
the governing DID method. equivalentId
represents a
full graph merge because the same DID document describes both the
equivalentId
DID and the id
property
DID.
If a requesting party does not retain the values from the id
and
equivalentId
properties and ensure any subsequent
interactions with any of the values they contain are correctly handled as
logically equivalent, there might be negative or unexpected issues that
arise. Implementers are strongly advised to observe the
directives related to this metadata property.
The canonicalId
property is identical to the
equivalentId
property except: a) it is associated with a
single value rather than a set, and b) the DID is defined to be
the canonical ID for the DID subject within the scope of the containing
DID document.
DID document metadata MAY include a canonicalId
property.
If present, the value MUST be a string that conforms to the rules in Section § 3.1 DID Syntax. The relationship is a statement that the
canonicalId
value is logically equivalent to the
id
property value and that the canonicalId
value is defined by the DID method to be the canonical ID for the DID
subject in the scope of the containing DID document. A
canonicalId
value MUST be produced by, and a form of, the
same DID method as the id
property value. (e.g.,
did:example:abc
== did:example:ABC
).
A conforming DID method specification MUST guarantee that the
canonicalId
value is logically equivalent to the
id
property value.
A requesting party is expected to use the canonicalId
value
as its primary ID value for the DID subject and treat all other
equivalent values as secondary aliases (e.g., update corresponding primary
references in their systems to reflect the new canonical ID directive).
canonicalId
is the same statement of equivalence as
equivalentId
except it is constrained to a single value that
is defined to be canonical for the DID subject in the scope of the DID
document. Like equivalentId
,
canonicalId
represents a full graph merge because the same
DID document describes both the canonicalId
DID and
the id
property DID.
If a resolving party does not use the canonicalId
value as
its primary ID value for the DID subject and treat all other equivalent values
as secondary aliases, there might be negative or unexpected issues that arise
related to user experience. Implementers are strongly advised to observe the
directives related to this metadata property.
The DID URL dereferencing function dereferences a DID URL into a resource with contents depending on the DID URL's components, including the DID method, method-specific identifier, path, query, and fragment. This process depends on DID resolution of the DID contained in the DID URL. DID URL dereferencing might involve multiple steps (e.g., when the DID URL being dereferenced includes a fragment), and the function is defined to return the final resource after all steps are completed. The details of how this process is accomplished are outside the scope of this specification. The following figure depicts the relationship described above.
The top left part of the diagram contains a rectangle with black outline, labeled "DID".
The bottom left part of the diagram contains a rectangle with black outline, labeled "DID URL". This rectangle contains four smaller black-outlined rectangles, aligned in a horizontal row adjacent to each other. These smaller rectangles are labeled, in order, "DID", "path", "query", and "fragment.
The top right part of the diagram contains a rectangle with black outline, labeled "DID document". This rectangle contains three smaller black-outlined rectangles. These smaller rectangles are labeled "id", "(property X)", and "(property Y)", and are surrounded by multiple series of three dots (ellipses). A curved black arrow, labeled "DID document - relative fragment dereference", extends from the rectangle labeled "(property X)", and points to the rectangle labeled "(property Y)".
The bottom right part of the diagram contains an oval shape with black outline, labeled "Resource".
A black arrow, labeled "resolves to a DID document", extends from the rectangle in the top left part of the diagram, labeled "DID", and points to the rectangle in the top right part of diagram, labeled "DID document".
A black arrow, labeled "refers to", extends from the rectangle in the top right part of the diagram, labeled "DID document", and points to the oval shape in the bottom right part of diagram, labeled "Resource".
A black arrow, labeled "contains", extends from the small rectangle labeled "DID" inside the rectangle in the bottom left part of the diagram, labeled "DID URL", and points to the rectangle in the top left part of diagram, labeled "DID".
A black arrow, labeled "dereferences to a DID document", extends from the rectangle in the bottom left part of the diagram, labeled "DID URL", and points to the rectangle in the top right part of diagram, labeled "DID document".
A black arrow, labeled "dereferences to a resource", extends from the rectangle in the bottom left part of the diagram, labeled "DID URL", and points to the oval shape in the bottom right part of diagram, labeled "Resource".
All conforming DID resolvers implement the following function which has the following abstract form:
dereference(didUrl, dereferenceOptions) →
« dereferencingMetadata, contentStream, contentMetadata »
The input variables of the dereference
function are as follows:
While it is valid for any didUrl
to be passed to a DID URL
dereferencer, implementers are expected to refer to [DID-RESOLUTION] to
further understand common patterns for how a DID URL is expected
to be dereferenced.
dereference
function in addition to the
didUrl
itself. Properties defined by this specification are in § 7.2.1 DID URL Dereferencing Options. This input is REQUIRED, but the
structure MAY be empty.
This function returns multiple values, and no limitations
are placed on how these values are returned together.
The return values of the dereference
include
dereferencingMetadata
, contentStream
,
and contentMetadata
:
error
property
describing the error.
dereferencing
function was called and successful, this MUST
contain a resource corresponding to the DID URL. The
contentStream
MAY be a resource such as a DID
document that is serializable in one of the conformant
representations, a Verification
Method, a service, or any other resource format that
can be identified via a Media Type and obtained through the resolution process.
If the dereferencing is unsuccessful, this value MUST be empty.
contentStream
. If the contentStream
is a DID document, this MUST be a didDocumentMetadata structure as
described in DID Resolution. If the dereferencing is unsuccessful, this
output MUST be an empty metadata structure.
Conforming DID URL dereferencing implementations do not alter the
signature of these functions in any way. DID URL dereferencing
implementations might map the dereference
function to a
method-specific internal function to perform the actual DID URL
dereferencing process. DID URL dereferencing implementations might
implement and expose additional functions with different signatures in addition
to the dereference
function specified here.
The possible properties within this structure and their possible values SHOULD be registered in the DID Specification Registries [DID-SPEC-REGISTRIES]. This specification defines the following common properties for dereferencing options:
contentStream
. The Media
Type MUST be expressed as an ASCII string. The
DID URL dereferencing implementation SHOULD use this value to determine
the contentType
of the representation contained in the
returned value if such a representation is supported and available.
The possible properties within this structure and their possible values are registered in the DID Specification Registries [DID-SPEC-REGISTRIES]. This specification defines the following common properties.
contentStream
SHOULD be expressed
using this property if dereferencing is successful. The Media
Type value MUST be expressed as an ASCII string.
contentStream
resulting from this dereferencing request.
Input and output metadata is often involved during the DID Resolution, DID URL dereferencing, and other DID-related processes. The structure used to communicate this metadata MUST be a map of properties. Each property name MUST be a string. Each property value MUST be a string, map, list, set, boolean, or null. The values within any complex data structures such as maps and lists MUST be one of these data types as well. All metadata property definitions registered in the DID Specification Registries [DID-SPEC-REGISTRIES] MUST define the value type, including any additional formats or restrictions to that value (for example, a string formatted as a date or as a decimal integer). It is RECOMMENDED that property definitions use strings for values. The entire metadata structure MUST be serializable according to the JSON serialization rules in the [INFRA] specification. Implementations MAY serialize the metadata structure to other data formats.
All implementations of functions that use metadata structures as either input or output are able to fully represent all data types described here in a deterministic fashion. As inputs and outputs using metadata structures are defined in terms of data types and not their serialization, the method for representation is internal to the implementation of the function and is out of scope of this specification.
The following example demonstrates a JSON-encoded metadata structure that might be used as DID resolution input metadata.
{
"accept": "application/did+ld+json"
}
This example corresponds to a metadata structure of the following format:
«[
"accept" → "application/did+ld+json"
]»
The next example demonstrates a JSON-encoded metadata structure that might be used as DID resolution metadata if a DID was not found.
{
"error": "notFound"
}
This example corresponds to a metadata structure of the following format:
«[
"error" → "notFound"
]»
The next example demonstrates a JSON-encoded metadata structure that might be used as DID document metadata to describe timestamps associated with the DID document.
{
"created": "2019-03-23T06:35:22Z",
"updated": "2023-08-10T13:40:06Z"
}
This example corresponds to a metadata structure of the following format:
«[
"created" → "2019-03-23T06:35:22Z",
"updated" → "2023-08-10T13:40:06Z"
]»
A DID method defines how implementers can realize the features described by this specification. DID methods are often associated with a particular verifiable data registry. New DID methods are defined in their own specifications to enable interoperability between different implementations of the same DID method.
Conceptually, the relationship between this specification and a DID
method specification is similar to the relationship between the IETF generic
URI specification [RFC3986] and a specific URI scheme
[IANA-URI-SCHEMES], such as the http
scheme [RFC7230]. In
addition to defining a specific DID scheme, a DID method
specification also defines the mechanisms for creating, resolving, updating, and
deactivating DIDs and DID documents using a specific type of
verifiable data registry. It also documents all implementation
considerations related to DIDs as well as Security and Privacy
Considerations.
This section specifies the requirements for authoring DID method specifications.
The requirements for all DID method specifications when defining the method-specific DID Syntax are as follows:
method-name
rule in § 3.1 DID Syntax.
method-specific-id
component of a DID.
method-specific-id
.
method-specific-id
value MUST be unique within a DID
method. The method-specific-id
value itself might be globally
unique.
method-name
conflicts, a DID method
specification SHOULD be registered in the DID Specification Registries
[DID-SPEC-REGISTRIES].
method-specific-id
formats.
method-specific-id
format MAY include colons. The use of
colons MUST comply syntactically with the method-specific-id
ABNF
rule.
The meaning of colons in the method-specific-id
is entirely
method-specific. Colons might be used by DID methods for establishing
hierarchically partitioned namespaces, for identifying specific instances or
parts of the verifiable data registry, or for other purposes.
Implementers are advised to avoid assuming any meanings or
behaviors associated with a colon that are generically applicable to all
DID methods.
The requirements for all DID method specifications when defining the method operations are as follows:
The authority of a party that is performing authorization to carry out the operations is specific to a DID method. For example, a DID method might —
controller
property.
authentication
.
capabilityInvocation
verification relationship.
The requirements for all DID method specifications when authoring the Security Considerations section are as follows:
The requirements for all DID method specifications when authoring the Privacy Considerations section are:
This section is non-normative.
This section contains a variety of security considerations that people using Decentralized Identifiers are advised to consider before deploying this technology in a production setting. DIDs are designed to operate under the threat model used by many IETF standards and documented in [RFC3552]. This section elaborates upon a number of the considerations in [RFC3552], as well as other considerations that are unique to DID architecture.
The DID Specification Registries [DID-SPEC-REGISTRIES] contains an informative list of DID method names and their corresponding DID method specifications. Implementers need to bear in mind that there is no central authority to mandate which DID method specification is to be used with any specific DID method name. If there is doubt on whether or not a specific DID resolver implements a DID method correctly, the DID Specification Registries can be used to look up the registered specification and make an informed decision regarding which DID resolver implementation to use.
Binding an entity in the digital world or the physical world to a DID, to a DID document, or to cryptographic material requires, the use of security protocols contemplated by this specification. The following sections describe some possible scenarios and how an entity therein might prove control over a DID or a DID document for the purposes of authentication or authorization.
Proving control over a DID and/or a DID Document is useful when updating either in a verifiable data registry or authenticating with remote systems. Cryptographic digital signatures and verifiable timestamps enable certain security protocols related to DID documents to be cryptographically verifiable. For these purposes, this specification defines useful verification relationships in § 5.3.1 Authentication and § 5.3.4 Capability Invocation. The secret cryptographic material associated with the verification methods can be used to generate a cryptographic digital signature as a part of an authentication or authorization security protocol.
Some DID methods allow digital signatures and other proofs to be included in the DID document or a § 7.3 Metadata Structure. However, such proofs by themselves do not necessarily prove control over a DID, or guarantee that the DID document is the correct one for the DID. In order to obtain the correct DID document and verify control over a DID, it is necessary to perform the DID resolution process as defined by the DID method.
A DID and DID document do not inherently carry any personal data and it is strongly advised that non-public entities do not publish personal data in DID documents.
It can be useful to express a binding of a DID to a person's or organization's physical identity in a way that is provably asserted by a trusted authority, such as a government. This specification provides the § 5.3.2 Assertion verification relationship for these purposes. This feature can enable interactions that are private and can be considered legally enforceable under one or more jurisdictions; establishing such bindings has to be carefully balanced against privacy considerations (see § 10. Privacy Considerations).
The process of binding a DID to something in the physical world, such as a person or an organization — for example, by using verifiable credentials with the same subject as that DID — is contemplated by this specification and further defined in the Verifiable Credentials Data Model [VC-DATA-MODEL].
If a DID document publishes a service intended for authentication or authorization of the DID subject (see Section § 5.4 Services), it is the responsibility of the service endpoint provider, subject, or requesting party to comply with the requirements of the authentication protocols supported at that service endpoint.
Non-repudiation of DIDs and DID document updates is supported if:
One mitigation against unauthorized changes to a DID document is monitoring and actively notifying the DID subject when there are changes. This is analogous to helping prevent account takeover on conventional username/password accounts by sending password reset notifications to the email addresses on file.
In the case of a DID, there is no intermediary registrar or account provider to generate such notifications. However, if the verifiable data registry on which the DID is registered directly supports change notifications, a subscription service can be offered to DID controllers. Notifications could be sent directly to the relevant service endpoints listed in an existing DID.
If a DID controller chooses to rely on a third-party monitoring service (other than the verifiable data registry itself), this introduces another vector of attack.
In a decentralized identifier architecture, there might not be centralized authorities to enforce cryptographic material or cryptographic digital signature expiration policies. Therefore, it is with supporting software such as DID resolvers and verification libraries that requesting parties validate that cryptographic material were not expired at the time they were used. Requesting parties might employ their own expiration policies in addition to inputs into their verification processes. For example, some requesting parties might accept authentications from five minutes in the past, while others with access to high precision time sources might require authentications to be time stamped within the last 500 milliseconds.
There are some requesting parties that have legitimate needs to extend the use of already-expired cryptographic material, such as verifying legacy cryptographic digital signatures. In these scenarios, a requesting party might instruct their verification software to ignore cryptographic key material expiration or determine if the cryptographic key material was expired at the time it was used.
Rotation is a management process that enables the secret cryptographic material associated with an existing verification method to be deactivated or destroyed once a new verification method has been added to the DID document. Going forward, any new proofs that a controller would have generated using the old secret cryptographic material can now instead be generated using the new cryptographic material and can be verified using the new verification method.
Rotation is a useful mechanism for protecting against verification method compromise, since frequent rotation of a verification method by the controller reduces the value of a single compromised verification method to an attacker. Performing revocation immediately after rotation is useful for verification methods that a controller designates for short-lived verifications, such as those involved in encrypting messages and authentication.
The following considerations might be of use when contemplating the use of verification method rotation:
Revocation is a management process that enables the secret cryptographic material associated with an existing verification method to be deactivated such that it ceases to be a valid form of creating new proofs of digital signatures.
Revocation is a useful mechanism for reacting to a verification method compromise. Performing revocation immediately after rotation is useful for verification methods that a controller designates for short-lived verifications, such as those involved in encrypting messages and authentication.
Compromise of the secrets associated with a verification method allows the attacker to use them according to the verification relationship expressed by controller in the DID document, for example, for authentication. The attacker's use of the secrets might be indistinguishable from the legitimate controller's use starting from the time the verification method was registered, to the time it was revoked.
The following considerations might be of use when contemplating the use of verification method revocation:
Although verifiers might choose not to accept proofs or signatures from a revoked verification method, knowing whether a verification was made with a revoked verification method is trickier than it might seem. Some DID methods provide the ability to look back at the state of a DID at a point in time, or at a particular version of the DID document. When such a feature is combined with a reliable way to determine the time or DID version that existed when a cryptographically verifiable statement was made, then revocation does not undo that statement. This can be the basis for using DIDs to make binding commitments; for example, to sign a mortgage.
If these conditions are met, revocation is not retroactive; it only nullifies future use of the method.
However, in order for such semantics to be safe, the second condition — an ability to know what the state of the DID document was at the time the assertion was made — is expected to apply. Without that guarantee, someone could discover a revoked key and use it to make cryptographically verifiable statements with a simulated date in the past.
Some DID methods only allow the retrieval of the current state of a DID. When this is true, or when the state of a DID at the time of a cryptographically verifiable statement cannot be reliably determined, then the only safe course is to disallow any consideration of DID state with respect to time, except the present moment. DID ecosystems that take this approach essentially provide cryptographically verifiable statements as ephemeral tokens that can be invalidated at any time by the DID controller.
Trustless systems are those where all trust is derived from cryptographically
provable assertions, and more specifically, where no metadata outside of the
cryptographic system is factored into the determination of trust in the system.
To verify a signature of proof for a verification method which has been
revoked in a trustless system, a DID method needs to support either or
both of the versionId
or versionTime
, as well as both the updated
and
nextUpdate
, DID document metadata properties. A verifier can validate a
signature or proof of a revoked key if and only if all of the following are
true:
versionId
or versionTime
of the DID
document that was used at the point the signature or proof was created.
updated
timestamp is
before, and the nextUpdate
timestamp is after, the point in time at which the
signature or proof was made.
In systems that are willing to admit metadata other than those constituting cryptographic input, similar trust may be achieved -- but always on the same basis where a careful judgment is made about whether a DID document's content at the moment of a signing event contained the expected content.
Recovery is a reactive security measure whereby a controller that has lost the ability to perform DID operations, such as through the loss of a device, is able to regain the ability to perform DID operations.
The following considerations might be of use when contemplating the use of DID recovery:
DIDs achieve global uniqueness without the need for a central registration authority. This comes at the cost of human memorability. Algorithms capable of generating globally unambiguous identifiers produce random strings of characters that have no human meaning. This trade-off is often referred to as Zooko's Triangle.
There are use cases where it is desirable to discover a DID when starting from a human-friendly identifier. For example, a natural language name, a domain name, or a conventional address for a DID controller, such as a mobile telephone number, email address, social media username, or blog URL. However, the problem of mapping human-friendly identifiers to DIDs, and doing so in a way that can be verified and trusted, is outside the scope of this specification.
Solutions to this problem are defined in separate specifications, such as [DNS-DID], that reference this specification. It is strongly recommended that such specifications carefully consider the:
If desired by a DID controller, a DID or a DID URL is capable of acting as persistent, location-independent resource identifier. These sorts of identifiers are classified as Uniform Resource Names (URNs) and are defined in [RFC8141]. DIDs are an enhanced form of URN that provide a cryptographically secure, location-independent identifier for a digital resource, while also providing metadata that enables retrieval. Due to the indirection between the DID document and the DID itself, the DID controller can adjust the actual location of the resource — or even provide the resource directly — without adjusting the DID. DIDs of this type can definitively verify that the resource retrieved is, in fact, the resource identified.
A DID controller who intends to use a DID for this purpose is advised to follow the security considerations in [RFC8141]. In particular:
Many cybersecurity abuses hinge on exploiting gaps between reality and the assumptions of rational, good-faith actors. Immutability of DID documents can provide some security benefits. Individual DID methods ought to consider constraints that would eliminate behaviors or semantics they do not need. The more locked down a DID method is, while providing the same set of features, the less it can be manipulated by malicious actors.
As an example, consider that a single edit to a DID document can change
anything except the root id
property of the document. But
is it actually desirable for a service to change its
type
after it is defined? Or for a key to change its value? Or
would it be better to require a new id
when certain
fundamental properties of an object change? Malicious takeovers of a website
often aim for an outcome where the site keeps its host name identifier,
but is subtly changed underneath. If certain properties of the site, such
as the ASN
associated with its IP address, were required by the specification to be
immutable, anomaly detection would be easier, and attacks would be much
harder and more expensive to carry out.
For DID methods tied to a global source of truth, a direct, just-in-time lookup of the latest version of a DID document is always possible. However, it seems likely that layers of cache might eventually sit between a DID resolver and that source of truth. If they do, believing the attributes of an object in the DID document to have a given state when they are actually subtly different might invite exploits. This is particularly true if some lookups are of a full DID document, and others are of partial data where the larger context is assumed.
Encryption algorithms have been known to fail due to advances in cryptography and computing power. Implementers are advised to assume that any encrypted data placed in a DID document might eventually be made available in clear text to the same audience to which the encrypted data is available. This is particularly pertinent if the DID document is public.
Encrypting all or parts of a DID document is not an appropriate means to protect data in the long term. Similarly, placing encrypted data in a DID document is not an appropriate means to protect personal data.
Given the caveats above, if encrypted data is included in a DID document, implementers are advised to not associate any correlatable information that could be used to infer a relationship between the encrypted data and an associated party. Examples of correlatable information include public keys of a receiving party, identifiers to digital assets known to be under the control of a receiving party, or human readable descriptions of a receiving party.
Given the equivalentId
and canonicalId
properties are generated by DID methods themselves, the same security and
accuracy guarantees that apply to the resolved DID present in the
id
field of a DID document also apply to these properties.
The alsoKnownAs
property is not guaranteed to be an accurate
statement of equivalence, and should not be relied upon without performing
validation steps beyond the resolution of the DID document.
The equivalentId
and canonicalId
properties express equivalence assertions to variants of a single DID
produced by the same DID method and can be trusted to the extent the
requesting party trusts the DID method and a conforming producer and
resolver.
The alsoKnownAs
property permits an equivalence assertion to
URIs that are not governed by the same DID method and cannot be
trusted without performing verification steps outside of the governing DID
method. See additional guidance in § 5.1.3 Also Known As.
As with any other security-related properties in the DID document, parties relying on any equivalence statement in a DID document should guard against the values of these properties being substituted by an attacker after the proper verification has been performed. Any write access to a DID document stored in memory or disk after verification has been performed is an attack vector that might circumvent verification unless the DID document is re-verified.
DID documents which include links to external machine-readable content such as images, web pages, or schemas are vulnerable to tampering. It is strongly advised that external links are integrity protected using solutions such as a hashlink [HASHLINK]. External links are to be avoided if they cannot be integrity protected and the DID document's integrity is dependent on the external link.
One example of an external link where the integrity of the DID document itself could be affected is the JSON-LD Context [JSON-LD11]. To protect against compromise, DID document consumers are advised to cache local static copies of JSON-LD contexts and/or verify the integrity of external contexts against a cryptographic hash that is known to be associated with a safe version of the external JSON-LD Context.
DIDs are designed to be persistent such that a controller need not rely upon a single trusted third party or administrator to maintain their identifiers. In an ideal case, no administrator can take control away from the controller, nor can an administrator prevent their identifiers' use for any particular purpose such as authentication, authorization, and attestation. No third party can act on behalf of a controller to remove or render inoperable an entity's identifier without the controller's consent.
However, it is important to note that in all DID methods that enable cryptographic proof-of-control, the means of proving control can always be transferred to another party by transferring the secret cryptographic material. Therefore, it is vital that systems relying on the persistence of an identifier over time regularly check to ensure that the identifier is, in fact, still under the control of the intended party.
Unfortunately, it is impossible to determine from the cryptography alone whether or not the secret cryptographic material associated with a given verification method has been compromised. It might well be that the expected controller still has access to the secret cryptographic material — and as such can execute a proof-of-control as part of a verification process — while at the same time, a bad actor also has access to those same keys, or to a copy thereof.
As such, cryptographic proof-of-control is expected to only be used as one factor in evaluating the level of identity assurance required for high-stakes scenarios. DID-based authentication provides much greater assurance than a username and password, thanks to the ability to determine control over a cryptographic secret without transmitting that secret between systems. However, it is not infallible. Scenarios that involve sensitive, high value, or life-critical operations are expected to use additional factors as appropriate.
In addition to potential ambiguity from use by different controllers, it is impossible to guarantee, in general, that a given DID is being used in reference to the same subject at any given point in time. It is technically possible for the controller to reuse a DID for different subjects and, more subtly, for the precise definition of the subject to either change over time or be misunderstood.
For example, consider a DID used for a sole proprietorship, receiving various credentials used for financial transactions. To the controller, that identifier referred to the business. As the business grows, it eventually gets incorporated as a Limited Liability Company. The controller continues using that same DID, because to them the DID refers to the business. However, to the state, the tax authority, and the local municipality, the DID no longer refers to the same entity. Whether or not the subtle shift in meaning matters to a credit provider or supplier is necessarily up to them to decide. In many cases, as long as the bills get paid and collections can be enforced, the shift is immaterial.
Due to these potential ambiguities, DIDs are to be considered valid contextually rather than absolutely. Their persistence does not imply that they refer to the exact same subject, nor that they are under the control of the same controller. Instead, one needs to understand the context in which the DID was created, how it is used, and consider the likely shifts in their meaning, and adopt procedures and policies to address both potential and inevitable semantic drift.
Additional information about the security context of authentication events is often required for compliance reasons, especially in regulated areas such as the financial and public sectors. This information is often referred to as a Level of Assurance (LOA). Examples include the protection of secret cryptographic material, the identity proofing process, and the form-factor of the authenticator.
Payment services (PSD 2) and eIDAS introduce such requirements to the security context. Level of assurance frameworks are classified and defined by regulations and standards such as eIDAS, NIST 800-63-3 and ISO/IEC 29115:2013, including their requirements for the security context, and making recommendations on how to achieve them. This might include strong user authentication where FIDO2/WebAuthn can fulfill the requirement.
Some regulated scenarios require the implementation of a specific level of
assurance. Since verification relationships such as
assertionMethod
and authentication
might be
used in some of these situations, information about the applied security context
might need to be expressed and provided to a verifier. Whether and how
to encode this information in the DID document data model is out of scope
for this specification. Interested readers might note that 1) the information
could be transmitted using Verifiable Credentials [VC-DATA-MODEL], and 2) the
DID document data model can be extended to incorporate this information
as described in § 4.1 Extensibility, and where § 10. Privacy Considerations is applicable for such extensions.
This section is non-normative.
Since DIDs and DID documents are designed to be administered directly by the DID controller(s), it is critically important to apply the principles of Privacy by Design [PRIVACY-BY-DESIGN] to all aspects of the decentralized identifier architecture. All seven of these principles have been applied throughout the development of this specification. The design used in this specification does not assume that there is a registrar, hosting company, nor other intermediate service provider to recommend or apply additional privacy safeguards. Privacy in this specification is preventive, not remedial, and is an embedded default. The following sections cover privacy considerations that implementers might find useful when building systems that utilize decentralized identifiers.
If a DID method specification is written for a public-facing verifiable data registry where corresponding DIDs and DID documents might be made publicly available, it is critical that those DID documents contain no personal data. Personal data can instead be transmitted through other means such as 1) Verifiable Credentials [VC-DATA-MODEL], or 2) service endpoints under control of the DID subject or DID controller.
Due diligence is expected to be taken around the use of URLs in service endpoints to prevent leakage of personal data or correlation within a URL of a service endpoint. For example, a URL that contains a username is dangerous to include in a DID Document because the username is likely to be human-meaningful in a way that can reveal information that the DID subject did not consent to sharing. With the privacy architecture suggested by this specification, personal data can be exchanged on a private, peer-to-peer basis using communication channels identified and secured by verification methods in DID documents. This also enables DID subjects and requesting parties to implement the GDPR right to be forgotten, because no personal data is written to an immutable distributed ledger.
Like any type of globally unambiguous identifier, DIDs might be used for correlation. DID controllers can mitigate this privacy risk by using pairwise DIDs that are unique to each relationship; in effect, each DID acts as a pseudonym. A pairwise DID need only be shared with more than one party when correlation is explicitly desired. If pairwise DIDs are the default, then the only need to publish a DID openly, or to share it with multiple parties, is when the DID controller(s) and/or DID subject explicitly desires public identification and correlation.
The anti-correlation protections of pairwise DIDs are easily defeated if the data in the corresponding DID documents can be correlated. For example, using identical verification methods or bespoke service endpoints in multiple DID documents can provide as much correlation information as using the same DID. Therefore, the DID document for a pairwise DID also needs to use pairwise unique information, such as ensuring that verification methods are unique to the pairwise relationship.
It might seem natural to also use pairwise unique service endpoints in the DID document for a pairwise DID. However, unique endpoints allow all traffic between two DIDs to be isolated perfectly into unique buckets, where timing correlation and similar analysis is easy. Therefore, a better strategy for endpoint privacy might be to share an endpoint among a large number of DIDs controlled by many different subjects (see § 10.5 Herd Privacy).
It is dangerous to add properties to the DID document that can be used to indicate, explicitly or through inference, what type or nature of thing the DID subject is, particularly if the DID subject is a person.
Not only do such properties potentially result in personal data (see § 10.1 Keep Personal Data Private) or correlatable data (see § 10.2 DID Correlation Risks and § 10.3 DID Document Correlation Risks) being present in the DID document, but they can be used for grouping particular DIDs in such a way that they are included in or excluded from certain operations or functionalities.
Including type information in a DID Document can result in personal privacy harms even for DID Subjects that are non-person entities, such as IoT devices. The aggregation of such information around a DID Controller could serve as a form of digital fingerprint and this is best avoided.
To minimize these risks, all properties in a DID document ought to be for expressing cryptographic material, endpoints, or verification methods related to using the DID.
When a DID subject is indistinguishable from others in the herd, privacy is available. When the act of engaging privately with another party is by itself a recognizable flag, privacy is greatly diminished.
DIDs and DID methods need to work to improve herd privacy, particularly for those who legitimately need it most. Choose technologies and human interfaces that default to preserving anonymity and pseudonymity. To reduce digital fingerprints, share common settings across requesting party implementations, keep negotiated options to a minimum on wire protocols, use encrypted transport layers, and pad messages to standard lengths.
The ability for a controller to optionally express at least one service endpoint in the DID document increases their control and agency. Each additional endpoint in the DID document adds privacy risk either due to correlation, such as across endpoint descriptions, or because the services are not protected by an authorization mechanism, or both.
DID documents are often public and, since they are standardized, will be stored and indexed efficiently by their very standards-based nature. This risk is worse if DID documents are published to immutable verifiable data registries. Access to a history of the DID documents referenced by a DID represents a form of traffic analysis made more efficient through the use of standards.
The degree of additional privacy risk caused by using multiple service
endpoints in one DID document can be difficult to estimate. Privacy
harms are typically unintended consequences. DIDs can refer to documents,
services, schemas, and other things that might be associated with
individual people, households, clubs, and employers — and correlation of
their service endpoints could become a powerful surveillance and
inference tool. An example of this potential harm can be seen when multiple
common country-level top level domains such as
https://example.co.uk
might be used to infer the approximate
location of the DID subject with a greater degree of probability.
The variety of possible endpoints makes it particularly challenging to maintain herd privacy, in which no information about the DID subject is leaked (see § 10.5 Herd Privacy).
First, because service endpoints might be specified as URIs, they could
unintentionally leak personal information because of the architecture of the
service. For example, a service endpoint of
http://example.com/MyFirstName
is leaking the term
MyFirstName
to everyone who can access the DID document.
When linking to legacy systems, this is an unavoidable risk, and care is
expected to be taken in such cases. This specification encourages new,
DID-aware endpoints to use nothing more than the DID itself for
any identification necessary. For example, if a service description were to
include http://example.com/did%3Aexample%3Aabc123
, no harm would be
done because did:example:abc123
is already exposed in the DID
Document; it leaks no additional information.
Second, because a DID document can list multiple service endpoints, it is possible to irreversibly associate services that are not associated in any other context. This correlation on its own may lead to privacy harms by revealing information about the DID subject, even if the URIs used did not contain any sensitive information.
Third, because some types of DID subjects might be more or less likely to list specific endpoints, the listing of a given service could, by itself, leak information that can be used to infer something about the DID subject. For example, a DID for an automobile might include a pointer to a public title record at the Department of Motor Vehicles, while a DID for an individual would not include that information.
It is the goal of herd privacy to ensure that the nature of specific DID subjects is obscured by the population of the whole. To maximize herd privacy, implementers need to rely on one — and only one — service endpoint, with that endpoint providing a proxy or mediator service that the controller is willing to depend on, to protect such associations and to blind requests to the ultimate service.
Given the concerns in the previous section, implementers are urged to consider any of the following service endpoint approaches:
These service endpoint types continue to be an area of innovation and exploration.
This section is non-normative.
See Verification Method Types [DID-SPEC-REGISTRIES] for optional extensions and other verification method types.
These examples are for information purposes only, it is considered a best practice to avoid using the same verification method for multiple purposes.
{
"@context": [
"https://www.w3.org/ns/did/v1",
"https://w3id.org/security/suites/ed25519-2020/v1"
],
"id": "did:example:123",
"authentication": [
{
"id": "did:example:123#z6MkecaLyHuYWkayBDLw5ihndj3T1m6zKTGqau3A51G7RBf3",
"type": "Ed25519VerificationKey2020", // external (property value)
"controller": "did:example:123",
"publicKeyMultibase": "zAKJP3f7BD6W4iWEQ9jwndVTCBq8ua2Utt8EEjJ6Vxsf"
}
],
"capabilityInvocation": [
{
"id": "did:example:123#z6MkhdmzFu659ZJ4XKj31vtEDmjvsi5yDZG5L7Caz63oP39k",
"type": "Ed25519VerificationKey2020", // external (property value)
"controller": "did:example:123",
"publicKeyMultibase": "z4BWwfeqdp1obQptLLMvPNgBw48p7og1ie6Hf9p5nTpNN"
}
],
"capabilityDelegation": [
{
"id": "did:example:123#z6Mkw94ByR26zMSkNdCUi6FNRsWnc2DFEeDXyBGJ5KTzSWyi",
"type": "Ed25519VerificationKey2020", // external (property value)
"controller": "did:example:123",
"publicKeyMultibase": "zHgo9PAmfeoxHG8Mn2XHXamxnnSwPpkyBHAMNF3VyXJCL"
}
],
"assertionMethod": [
{
"id": "did:example:123#z6MkiukuAuQAE8ozxvmahnQGzApvtW7KT5XXKfojjwbdEomY",
"type": "Ed25519VerificationKey2020", // external (property value)
"controller": "did:example:123",
"publicKeyMultibase": "z5TVraf9itbKXrRvt2DSS95Gw4vqU3CHAdetoufdcKazA"
}
]
}
{
"@context": [
"https://www.w3.org/ns/did/v1",
"https://w3id.org/security/suites/jws-2020/v1"
],
"verificationMethod": [
{
"id": "did:example:123#key-0",
"type": "JsonWebKey2020",
"controller": "did:example:123",
"publicKeyJwk": {
"kty": "OKP", // external (property name)
"crv": "Ed25519", // external (property name)
"x": "VCpo2LMLhn6iWku8MKvSLg2ZAoC-nlOyPVQaO3FxVeQ" // external (property name)
}
},
{
"id": "did:example:123#key-1",
"type": "JsonWebKey2020",
"controller": "did:example:123",
"publicKeyJwk": {
"kty": "OKP", // external (property name)
"crv": "X25519", // external (property name)
"x": "pE_mG098rdQjY3MKK2D5SUQ6ZOEW3a6Z6T7Z4SgnzCE" // external (property name)
}
},
{
"id": "did:example:123#key-2",
"type": "JsonWebKey2020",
"controller": "did:example:123",
"publicKeyJwk": {
"kty": "EC", // external (property name)
"crv": "secp256k1", // external (property name)
"x": "Z4Y3NNOxv0J6tCgqOBFnHnaZhJF6LdulT7z8A-2D5_8", // external (property name)
"y": "i5a2NtJoUKXkLm6q8nOEu9WOkso1Ag6FTUT6k_LMnGk" // external (property name)
}
},
{
"id": "did:example:123#key-3",
"type": "JsonWebKey2020",
"controller": "did:example:123",
"publicKeyJwk": {
"kty": "EC", // external (property name)
"crv": "secp256k1", // external (property name)
"x": "U1V4TVZVMUpUa0ZVU1NBcU9CRm5IbmFaaEpGNkxkdWx", // external (property name)
"y": "i5a2NtJoUKXkLm6q8nOEu9WOkso1Ag6FTUT6k_LMnGk" // external (property name)
}
},
{
"id": "did:example:123#key-4",
"type": "JsonWebKey2020",
"controller": "did:example:123",
"publicKeyJwk": {
"kty": "EC", // external (property name)
"crv": "P-256", // external (property name)
"x": "Ums5WVgwRkRTVVFnU3k5c2xvZllMbEcwM3NPRW91ZzN", // external (property name)
"y": "nDQW6XZ7b_u2Sy9slofYLlG03sOEoug3I0aAPQ0exs4" // external (property name)
}
},
{
"id": "did:example:123#key-5",
"type": "JsonWebKey2020",
"controller": "did:example:123",
"publicKeyJwk": {
"kty": "EC", // external (property name)
"crv": "P-384", // external (property name)
"x": "VUZKSlUwMGdpSXplekRwODhzX2N4U1BYdHVYWUZsaXVDR25kZ1U0UXA4bDkxeHpE", // external (property name)
"y": "jq4QoAHKiIzezDp88s_cxSPXtuXYFliuCGndgU4Qp8l91xzD1spCmFIzQgVjqvcP" // external (property name)
}
},
{
"id": "did:example:123#key-6",
"type": "JsonWebKey2020",
"controller": "did:example:123",
"publicKeyJwk": {
"kty": "EC", // external (property name)
"crv": "P-521", // external (property name)
"x": "VTI5c1lYSmZWMmx1WkhNZ0dQTXhaYkhtSnBEU3UtSXZwdUtpZ0VOMnB6Z1d0U28tLVJ3ZC1uNzhuclduWnplRGMx", // external (property name)
"y": "UW5WNVgwSnBkR052YVc0Z1VqY1B6LVpoZWNaRnliT3FMSUpqVk9sTEVUSDd1UGx5RzBnRW9NV25JWlhoUVZ5cFB5" // external (property name)
}
},
{
"id": "did:example:123#key-7",
"type": "JsonWebKey2020",
"controller": "did:example:123",
"publicKeyJwk": {
"kty": "RSA", // external (property name)
"e": "AQAB", // external (property name)
"n": "UkhWaGJGOUZRMTlFVWtKSElBdENGV2hlU1F2djFNRXh1NVJMQ01UNGpWazlraEpLdjhKZU1YV2UzYldIYXRqUHNrZGYyZGxhR2tXNVFqdE9uVUtMNzQybXZyNHRDbGRLUzNVTElhVDFoSkluTUhIeGoyZ2N1Yk82ZUVlZ0FDUTRRU3U5TE8wSC1MTV9MM0RzUkFCQjdRamE4SGVjcHl1c3BXMVR1X0RicXhjU253ZW5kYW13TDUyVjE3ZUtobE80dVh3djJIRmx4dWZGSE0wS21DSnVqSUt5QXhqRF9tM3FfX0lpSFVWSEQxdERJRXZMUGhHOUF6c24zajk1ZC1zYU" // external (property name)
}
}
]
}
{
"@context": [
"https://www.w3.org/ns/did/v1",
"https://w3id.org/security/suites/ed25519-2018/v1",
"https://w3id.org/security/suites/x25519-2019/v1",
"https://w3id.org/security/suites/secp256k1-2019/v1",
"https://w3id.org/security/suites/jws-2020/v1"
],
"verificationMethod": [
{
"id": "did:example:123#key-0",
"type": "Ed25519VerificationKey2018",
"controller": "did:example:123",
"publicKeyBase58": "3M5RCDjPTWPkKSN3sxUmmMqHbmRPegYP1tjcKyrDbt9J" // external (property name)
},
{
"id": "did:example:123#key-1",
"type": "X25519KeyAgreementKey2019",
"controller": "did:example:123",
"publicKeyBase58": "FbQWLPRhTH95MCkQUeFYdiSoQt8zMwetqfWoxqPgaq7x" // external (property name)
},
{
"id": "did:example:123#key-2",
"type": "EcdsaSecp256k1VerificationKey2019",
"controller": "did:example:123",
"publicKeyBase58": "ns2aFDq25fEV1NUd3wZ65sgj5QjFW8JCAHdUJfLwfodt" // external (property name)
},
{
"id": "did:example:123#key-3",
"type": "JsonWebKey2020",
"controller": "did:example:123",
"publicKeyJwk": {
"kty": "EC", // external (property name)
"crv": "P-256", // external (property name)
"x": "Er6KSSnAjI70ObRWhlaMgqyIOQYrDJTE94ej5hybQ2M", // external (property name)
"y": "pPVzCOTJwgikPjuUE6UebfZySqEJ0ZtsWFpj7YSPGEk" // external (property name)
}
}
]
}
This section is non-normative.
These examples are for information purposes only. See W3C Verifiable Credentials Data Model for additional examples.
{ // external (all terms in this example)
"@context": [
"https://www.w3.org/2018/credentials/v1",
"https://w3id.org/citizenship/v1"
],
"type": [
"VerifiableCredential",
"PermanentResidentCard"
],
"credentialSubject": {
"id": "did:example:123",
"type": [
"PermanentResident",
"Person"
],
"givenName": "JOHN",
"familyName": "SMITH",
"gender": "Male",
"image": "data:image/png;base64,iVBORw0KGgo...kJggg==",
"residentSince": "2015-01-01",
"lprCategory": "C09",
"lprNumber": "000-000-204",
"commuterClassification": "C1",
"birthCountry": "Bahamas",
"birthDate": "1958-08-17"
},
"issuer": "did:example:456",
"issuanceDate": "2020-04-22T10:37:22Z",
"identifier": "83627465",
"name": "Permanent Resident Card",
"description": "Government of Example Permanent Resident Card.",
"proof": {
"type": "Ed25519Signature2018",
"created": "2020-04-22T10:37:22Z",
"proofPurpose": "assertionMethod",
"verificationMethod": "did:example:456#key-1",
"jws": "eyJjcml0IjpbImI2NCJdLCJiNjQiOmZhbHNlLCJhbGciOiJFZERTQSJ9..BhWew0x-txcroGjgdtK-yBCqoetg9DD9SgV4245TmXJi-PmqFzux6Cwaph0r-mbqzlE17yLebjfqbRT275U1AA"
}
}
{ // external (all terms in this example)
"@context": [
"https://www.w3.org/2018/credentials/v1",
"https://www.w3.org/2018/credentials/examples/v1"
],
"id": "http://example.gov/credentials/3732",
"type": ["VerifiableCredential", "UniversityDegreeCredential"],
"issuer": { "id": "did:example:123" },
"issuanceDate": "2020-03-10T04:24:12.164Z",
"credentialSubject": {
"id": "did:example:456",
"degree": {
"type": "BachelorDegree",
"name": "Bachelor of Science and Arts"
}
},
"proof": {
"type": "JsonWebSignature2020",
"created": "2020-02-15T17:13:18Z",
"verificationMethod": "did:example:123#_Qq0UL2Fq651Q0Fjd6TvnYE-faHiOpRlPVQcY_-tA4A",
"proofPurpose": "assertionMethod",
"jws": "eyJiNjQiOmZhbHNlLCJjcml0IjpbImI2NCJdLCJhbGciOiJFZERTQSJ9..Y0KqovWCPAeeFhkJxfQ22pbVl43Z7UI-X-1JX32CA9MkFHkmNprcNj9Da4Q4QOl0cY3obF8cdDRdnKr0IwNrAw"
}
}
{ // external (all terms in this example)
"@context": [
"https://www.w3.org/2018/credentials/v1",
"https://w3id.org/security/bbs/v1",
{
"name": "https://schema.org/name",
"birthDate": "https://schema.org/birthDate"
}
],
"id": "urn:uuid:c499e122-3ba9-4e95-8d4d-c0ebfcf8c51a",
"type": ["VerifiableCredential"],
"issuanceDate": "2021-02-07T16:02:08.571Z",
"issuer": {
"id": "did:example:123"
},
"credentialSubject": {
"id": "did:example:456",
"name": "John Smith",
"birthDate": "2021-02-07"
},
"proof": {
"type": "BbsBlsSignature2020",
"created": "2021-02-07T16:02:10Z",
"proofPurpose": "assertionMethod",
"proofValue": "o7zD2eNTp657YzkJLub+IO4Zqy/R3Lv/AWmtSA/kUlEAOa73BNyP1vOeoow35jkABolx4kYMKkp/ZsFDweuKwe/p9vxv9wrMJ9GpiOZjHcpjelDRRJLBiccg9Yv7608mHgH0N1Qrj14PZ2saUlfhpQ==",
"verificationMethod": "did:example:123#bls12381-g2-key"
}
}
{ // external (all terms in this example)
"@context": [
"https://www.w3.org/2018/credentials/v1",
"https://w3id.org/security/bbs/v1",
{
"name": "https://schema.org/name",
"birthDate": "https://schema.org/birthDate"
}
],
"id": "urn:uuid:c499e122-3ba9-4e95-8d4d-c0ebfcf8c51a",
"type": "VerifiableCredential",
"issuanceDate": "2021-02-07T16:02:08.571Z",
"issuer": {
"id": "did:example:123"
},
"credentialSubject": {
"id": "did:example:456",
"birthDate": "2021-02-07"
},
"proof": {
"type": "BbsBlsSignatureProof2020",
"created": "2021-02-07T16:02:10Z",
"nonce": "OqZHsV/aunS34BhLaSoxiHWK+SUaG4iozM3V+1jO06zRRNcDWID+I0uwtPJJ767Yo8Q=",
"proofPurpose": "assertionMethod",
"proofValue": "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",
"verificationMethod": "did:example:123#bls12381-g2-key"
}
}
{ // external (all terms in this example)
"protected": {
"kid": "did:example:123#_Qq0UL2Fq651Q0Fjd6TvnYE-faHiOpRlPVQcY_-tA4A",
"alg": "EdDSA"
},
"payload": {
"iss": "did:example:123",
"sub": "did:example:456",
"vc": {
"@context": [
"https://www.w3.org/2018/credentials/v1",
"https://www.w3.org/2018/credentials/examples/v1"
],
"id": "http://example.gov/credentials/3732",
"type": [
"VerifiableCredential",
"UniversityDegreeCredential"
],
"issuer": {
"id": "did:example:123"
},
"issuanceDate": "2020-03-10T04:24:12.164Z",
"credentialSubject": {
"id": "did:example:456",
"degree": {
"type": "BachelorDegree",
"name": "Bachelor of Science and Arts"
}
}
},
"jti": "http://example.gov/credentials/3732",
"nbf": 1583814252
},
"signature": "qSv6dpZJGFybtcifLwGf4ujzlEu-fam_M7HPxinCbVhz9iIJCg70UMeQbPa1ex6BmQ2tnSS7F11FHnMB2bJRAw"
}
This section is non-normative.
These examples are for information purposes only, it is considered a best practice to avoid dislosing unnecessary information in JWE headers.
{ // external (all terms in this example)
"ciphertext": "3SHQQJajNH6q0fyAHmw...",
"iv": "QldSPLVnFf2-VXcNLza6mbylYwphW57Q",
"protected": "eyJlbmMiOiJYQzIwUCJ9",
"recipients": [
{
"encrypted_key": "BMJ19zK12YHftJ4sr6Pz1rX1HtYni_L9DZvO1cEZfRWDN2vXeOYlwA",
"header": {
"alg": "ECDH-ES+A256KW",
"apu": "Tx9qG69ZfodhRos-8qfhTPc6ZFnNUcgNDVdHqX1UR3s",
"apv": "ZGlkOmVsZW06cm9wc3RlbjpFa...",
"epk": {
"crv": "X25519",
"kty": "OKP",
"x": "Tx9qG69ZfodhRos-8qfhTPc6ZFnNUcgNDVdHqX1UR3s"
},
"kid": "did:example:123#zC1Rnuvw9rVa6E5TKF4uQVRuQuaCpVgB81Um2u17Fu7UK"
}
}
],
"tag": "xbfwwDkzOAJfSVem0jr1bA"
}
Following is a diagram showing the relationships among § 4. Data Model, § 5. Core Properties, and § 8. Methods, and § 7. Resolution.
The creation of a DID is a process that is defined by each DID
Method. Some DID Methods, such as did:key
, are purely
generative, such that a DID and a DID document are generated by
transforming a single piece of cryptographic material into a conformant
representation. Other DID methods might require the use of a
verifiable data registry, where the DID and DID document
are recognized to exist by third parties only when the registration has been
completed, as defined by the respective DID method. Other processes
might be defined by the respective DID method.
A DID is a specific type of URI (Uniform Resource Identifier), so a DID can refer to any resource. Per [RFC3986]:
the term "resource" is used in a general sense for whatever might be identified by a URI. [...] A resource is not necessarily accessible via the Internet.
Resources can be digital or physical, abstract or concrete. Any resource that can be assigned a URI can be assigned a DID. The resource referred to by the DID is the DID subject.
The DID controller determines the DID subject. It is not expected to be possible to determine the DID subject from looking at the DID itself, as DIDs are generally only meaningful to machines, not human. A DID is unlikely to contain any information about the DID subject, so further information about the DID subject is only discoverable by resolving the DID to the DID document, obtaining a verifiable credential about the DID, or via some other description of the DID.
While the value of the id
property in the retrieved
DID document must always match the DID being resolved, whether
or not the actual resource to which the DID refers can change over time
is dependent upon the DID method. For example, a DID method
that permits the DID subject to change could be used to generate a
DID for the current occupant of a particular role—such as the CEO
of a company—where the actual person occupying the role can be different
depending on when the DID is resolved.
The DID refers to the DID subject and resolves to the DID document (by following the protocol specified by the DID method). The DID document is not a separate resource from the DID subject and does not have a URI separate from the DID. Rather the DID document is an artifact of DID resolution controlled by the DID controller for the purpose of describing the DID subject.
This distinction is illustrated by the graph model shown below.
Each property in a DID document is a statement by the DID controller that describes:
id
and alsoKnownAs
properties)
verificationMethod
and service
properties).
@context
property for a JSON-LD representation).
The only required property in a DID document is id
,
so that is the only statement guaranteed to be in a DID document.
That statement is illustrated in Figure 8
with a direct link between the DID and the DID subject.
Options for discovering more information about the DID subject depend
on the properties present in the DID document. If the
service
property is present, more information can be
requested from a service endpoint. For example, by querying a
service endpoint that supports verifiable credentials for one or more
claims (attributes) describing the DID subject.
Another option is to use the alsoKnownAs
property if it
is present in the DID document. The DID controller can use it
to provide a list of other URIs (including other DIDs) that refer to
the same DID subject. Resolving or dereferencing these URIs might yield
other descriptions or representations of the DID subject as
illustrated in the figure below.
If the DID subject is a digital resource that can be retrieved from the internet, a DID method can choose to construct a DID URL which returns a representation of the DID subject itself. For example, a data schema that needs a persistent, cryptographically verifiable identifier could be assigned a DID, and passing a specified DID parameter (see § 3.2.1 DID Parameters) could be used as a standard way to retrieve a representation of that schema.
Similarly, a DID can be used to refer to a digital resource (such as an image) that can be returned directly from a verifiable data registry if that functionality is supported by the applicable DID method.
If the controller of a web page or any other web resource wants to
assign it a persistent, cryptographically verifiable identifier, the
controller can give it a DID. For example, the author of a blog
hosted by a blog hosting company (under that hosting company's domain)
could create a DID for the blog. In the DID document, the
author can include the alsoKnownAs
property pointing to
the current URL of the blog, e.g.:
"alsoKnownAs": ["https://myblog.blogging-host.example/home"]
If the author subsequently moves the blog to a different hosting company (or to the author's own domain), the author can update the DID document to point to the new URL for the blog, e.g.:
"alsoKnownAs": ["https://myblog.example/"]
The DID effectively adds a layer of indirection for the blog URL. This layer of indirection is under the control of the author instead of under the control of an external administrative authority such as the blog hosting company. This is how a DID can effectively function as an enhanced URN (Uniform Resource Name)—a persistent identifier for an information resource whose network location might change over time.
To avoid confusion, it is helpful to classify DID subjects into two disjoint sets based on their relationship to the DID controller.
The first case, shown in Figure 10, is the common scenario where the DID subject is also the DID controller. This is the case when an individual or organization creates a DID to self-identify.
From a graph model perspective, even though the nodes identified as the DID controller and DID subject in Figure 10 are distinct, there is a logical arc connecting them to express a semantic equivalence relationship.
The second case is when the DID subject is a separate entity from the DID controller. This is the case when, for example, a parent creates and maintains control of a DID for a child; a corporation creates and maintains control of a DID for a subsidiary; or a manufacturer creates and maintains control of a DID for a product, an IoT device, or a digital file.
From a graph model perspective, the only difference from Set 1 that there is no equivalence arc relationship between the DID subject and DID controller nodes.
A DID document might have more than one DID controller. This can happen in one of two ways.
In this case, each of the DID controllers might act on its own, i.e., each one has full power to update the DID document independently. From a graph model perspective, in this configuration:
In the case of group control, the DID controllers are expected to act together in some fashion, such as when using a cryptographic algorithm that requires multiple digital signatures ("multi-sig") or a threshold number of digital signatures ("m-of-n"). From a functional standpoint, this option is similar to a single DID controller because, although each of the DID controllers in the DID controller group has its own graph node, the actual control collapses into a single logical graph node representing the DID controller group as shown in Figure 12.
This configuration will often apply when the DID subject is an organization, corporation, government agency, community, or other group that is not controlled by a single individual.
A DID document has exactly one DID which refers to
the DID subject. The DID is expressed as the value of the
id
property. This property value is immutable for
the lifetime of the
DID document.
However, it is possible that the resource identified by the DID, the DID subject, may change over time. This is under the exclusive authority of the DID controller. For more details, see section § 9.16 Persistence.
The DID controller for a DID document might change over time. However, depending on how it is implemented, a change in the DID controller might not be made apparent by changes to the DID document itself. For example, if the change is implemented through a shift in ownership of the underlying cryptographic keys or other controls used for one or more of the verification methods in the DID document, it might be indistinguishable from a standard key rotation.
On the other hand, if the change is implemented by changing the value of the
controller
property, it will be transparent.
If it is important to verify a change of DID controller, implementers are advised to authenticate the new DID controller against the verification methods in the revised DID document.
This section contains the changes that have been made since the publication of this specification as a W3C First Public Working Draft.
Changes since the Second Candidate Recommendation include:
publicKeyMultibase
.
Changes since the First Candidate Recommendation include:
method-specific-id
ABNF rule
and for nextUpdate
and nextVersionId
.
equivalentId
and canonicalId
are optional.
publicKeyBase58
with publicKeyMultibase
.
Changes since the First Public Working Draft include:
The Working Group extends deep appreciation and heartfelt thanks to our Chairs Brent Zundel and Dan Burnett, as well as our W3C Staff Contact, Ivan Herman, for their tireless work in keeping the Working Group headed in a productive direction and navigating the deep and dangerous waters of the standards process.
Portions of the work on this specification have been funded by the United States Department of Homeland Security's (US DHS) Science and Technology Directorate under contracts HSHQDC-16-R00012-H-SB2016-1-002, and HSHQDC-17-C-00019, as well as the US DHS Silicon Valley Innovation Program under contracts 70RSAT20T00000010, 70RSAT20T00000029, 70RSAT20T00000030, 70RSAT20T00000045, 70RSAT20T00000003, and 70RSAT20T00000033. The content of this specification does not necessarily reflect the position or the policy of the U.S. Government and no official endorsement should be inferred.
Portions of the work on this specification have also been funded by the European Union's StandICT.eu program under sub-grantee contract number CALL05/19. The content of this specification does not necessarily reflect the position or the policy of the European Union and no official endorsement should be inferred.
Work on this specification has also been supported by the Rebooting the Web of Trust community facilitated by Christopher Allen, Shannon Appelcline, Kiara Robles, Brian Weller, Betty Dhamers, Kaliya Young, Kim Hamilton Duffy, Manu Sporny, Drummond Reed, Joe Andrieu, and Heather Vescent. Development of this specification has also been supported by the W3C Credentials Community Group, which has been Chaired by Kim Hamilton Duffy, Joe Andrieu, Christopher Allen, Heather Vescent, and Wayne Chang.
The Working Group thanks the following individuals for their contributions to
this specification (in alphabetical order, Github handles start with @
and
are sorted as last names): Denis Ah-Kang, Nacho Alamillo, Christopher Allen, Joe
Andrieu, Antonio, Phil Archer, George Aristy, Baha, Juan Benet, BigBlueHat, Dan
Bolser, Chris Boscolo, Pelle Braendgaard, Daniel Buchner, Daniel Burnett, Juan
Caballero, @cabo, Tim Cappalli, Melvin Carvalho, David Chadwick, Wayne Chang,
Sam Curren, Hai Dang, Tim Daubenschütz, Oskar van Deventer, Kim Hamilton Duffy,
Arnaud Durand, Ken Ebert, Veikko Eeva, @ewagner70, Carson Farmer, Nikos Fotiou,
Gabe, Gayan, @gimly-jack, @gjgd, Ryan Grant, Peter Grassberger, Adrian Gropper,
Amy Guy, Daniel Hardman, Kyle Den Hartog, Philippe Le Hegaret, Ivan Herman,
Michael Herman, Alen Horvat, Dave Huseby, Marcel Jackisch, Mike Jones, Andrew
Jones, Tom Jones, jonnycrunch, Gregg Kellogg, Michael Klein, @kdenhartog-sybil1,
Paul Knowles, @ktobich, David I. Lehn, Charles E. Lehner, Michael Lodder,
@mooreT1881, Dave Longley, Tobias Looker, Wolf McNally, Robert Mitwicki, Mircea
Nistor, Grant Noble, Mark Nottingham, @oare, Darrell O'Donnell, Vinod Panicker,
Dirk Porsche, Praveen, Mike Prorock, @pukkamustard, Drummond Reed, Julian
Reschke, Yancy Ribbens, Justin Richer, Rieks, @rknobloch, Mikeal Rogers,
Evstifeev Roman, Troy Ronda, Leonard Rosenthol, Michael Ruminer, Markus
Sabadello, Cihan Saglam, Samu, Rob Sanderson, Wendy Seltzer, Mehran Shakeri,
Jaehoon (Ace) Shim, Samuel Smith, James M Snell, SondreB, Manu Sporny, @ssstolk,
Orie Steele, Shigeya Suzuki, Sammotic Switchyarn, @tahpot, Oliver Terbu, Ted
Thibodeau Jr., Joel Thorstensson, Tralcan, Henry Tsai, Rod Vagg, Mike Varley,
Kaliya "Identity Woman" Young, Eric Welton, Fuqiao Xue, @Yue, Dmitri Zagidulin,
@zhanb, and Brent Zundel.
This section will be submitted to the Internet Engineering Steering Group (IESG) for review, approval, and registration with IANA when this specification becomes a W3C Proposed Recommendation.
Fragment identifiers used with application/did+json are treated according to the rules defined in § Fragment.
The Candidate Recommendation phase for this specification received a significant
number of implementations for the application/did+ld+json
media
type. Registration of the media type application/did+ld+json
at
IANA is pending resolution of the
Media Types with Multiple Suffixes issue. Work is expected to continue in
the IETF Media Type
Maintenance Working Group with a registration of the
application/did+ld+json
media type by W3C following shortly after
the publication of the
Media Types with Multiple Suffixes RFC.
Fragment identifiers used with application/did+ld+json are treated according to the rules associated with the JSON-LD 1.1: application/ld+json media type [JSON-LD11].
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