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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="https://www.w3.org/Tools/respec/respec-w3c" class="remove" defer></script>
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name: "José San Juan",
url: "https://gataca.io",
mailto: "[email protected]"
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shortName: "vui",
xref: "web-platform",
group: "Verifier Universal Interfaces",
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src: "https://cdn2.hubspot.net/hubfs/4728390/GATACA_ISOTYPE_GRADIENT.png",
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alt: "GATACA",
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id: "gataca-logo",
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<body>
<h1 id="title">Verifier Universal Interface</h1>
<h2 id="subtitle">Definition of the standards and interfaces that might be consumed by any verifier to be
interoperable with any wallet</h2>
<section id="abstract">
<p>
Decentralized digital identity, or "self-sovereign" identity (SSI), is a new paradigm proposed for managing
digital identities. Relying on Decentralized identifiers (DIDs) and Verifiable Credentials (VC), the subject
and his personal credentials are independent from any centralized registry,
identity provider, or certificate authority.
</p>
<p>
On the Decentralized Identity model, the role associated to requesting and verifying credentials is
defined as the Verifier.
</p>
<dd>
The verifier functionality is to support the data collector as it tries to acquire credentials from some
other party for the purpose of negotiating a business transaction. It does so by creating presentation
requests (or Presentation Definition as it is called in the draft DIF specfication for Presentation
Exchange) that ask for such credentials, sending them to a holder component of another party, receiving
a
response to such a request (which we call a 'presentation'), verifying the presentation, i.e. checking
the
signature and other proofs of the veracity of both the construction of the presentation as well as its
contents, thus providing the party with verified data.
</dd>
<p>
This document specifies the interfaces that MAY be consumed by any verifier allowing him to be interoperable
with any wallet fulfilling this interface; regardless of :
<ul>
<li>
The vendor of the technology
</li>
<li>
The technology stack used
</li>
<li>
The SSI governance framework in use
</li>
</ul>
</p>
<p class="ednote">
Despite its format, this document doesn't aim to be publish on the W3C as a standard normative, rather to
propose a universal interfaces for a verifier. This format is however extremely adequate to allow to work
and contribute
on the protocol definition.
</p>
</section>
<section id="sotd">
<p> </p>
</section>
<section data-dfn-for="Context">
<h1>Context</h1>
<p>
As different technology providers are offering SSI Solutions, it becomes a relevant matter to ensure
interoperability between those providers. On a not yet stable market, most providers aim to offer the whole
SSI stack: components for holders, verifiers, issuers and did-resolver.
</p>
<p>
In order to avoid vendor lock-ins, the APIs exploited by the Verifiers component can be standarized. This
document aims to offer the sufficient capabilities for a Verifier component of some technology provider to
use the technology stack of another SSI provider.
</p>
<section id="conformance">
</section>
<section id="terminology">
<h2>Terminology</h2>
<dl>
<dt><dfn data-lt="DID|DIDs|decentralized identifiers">Decentralized Identifier</dfn> (DID)</dt>
<dd>As defined in [[DID-CORE]].</dd>
<dt><dfn data-lt="">DID document</dfn></dt>
<dd>As defined in [[DID-CORE]].</dd>
<dt><dfn data-lt="">DID resolution</dt>
<dd>As defined in [[DID-RESOLUTION]].</dd>
<dt><dfn data-lt="DID resolver's">DID resolver</dt>
<dd>As defined in [[DID-RESOLUTION]].</dd>
<dt><dfn data-lt="VC|Verifiable Credential">Verifiable Credential</dfn> (VC)</dt>
<dd>As defined in [[VC-DATA-MODEL]].</dd>
<dt><dfn data-lt="VP|Verifiable Presentation">Verifiable Presentation</dfn> (VP)</dt>
<dd>As defined in [[VC-DATA-MODEL]].</dd>
<dt><dfn data-lt="Schema Registry|Credential Catalog">Schema Registry</dfn></dt>
<dd> See Section <a href="#registries"></a>.</dd>
<dt><dfn data-lt="Issuer Registry|Issuer Catalog">Issuer Registry</dfn></dt>
<dd> See Section <a href="#registries"></a>.</dd>
<dt><dfn data-lt="Presentation Request|PR">Presentation Request</dfn> (PR)</dt>
<dd> See Section <a href="#presentation-exchange"></a>.</dd>
</dl>
</section>
<section data-dfn-for="Operations" class="informative">
<h2>Verifier operations</h2>
<p>
Any Verifier MUST perform the following operations:
<ol class="oplist">
<li>
Request and receive specific information to holders in the form of Verifiable Credentials (presented
in a Verifiable Presentation)
</li>
<li>
Verify received VCs. That includes:
<ol>
<li>
Verify the proofs of every credential
</li>
<li>
Verify the proof of the presentation
</li>
<li>
Verify that the information received matches the information requested
</li>
</ol>
</li>
</ol>
Additionally, any Verifier SHALL perform the following operations:
<ol start="2" class="oplist start2">
<li>
While verifying the received VCs:
<ol start="4" class="oplist start4">
<li>
Verify the Issuer of the credential
<ol class="oplist">
<li>
Its authority over the credential
</li>
<li>
Its associated trust level
</li>
</ol>
</li>
<li>
Verify the status of every credential
</li>
<li>
Verify and match the ownership of the Verifiable Credentials and the Verifiable Presentation
</li>
<li>
Verify that all credentials can be linked to the same entity
</li>
<li>
Verify that the credentials requested satisfy some stablished constraints
</li>
</ol>
</li>
<li>
Verify that the credentials have been handled from a secure wallet
</li>
<li>
Authenticate the wallet owner
</li>
<li>
Manage the consent of the usage of the information inside the credentials
</li>
<li>
Ensure user anonimity and non external traceability
</li>
<li>
Manage selective disclosure of the information contained on the credentials
</li>
</ol>
</p>
</section>
</section>
<section data-dfn-for="Interfaces" class="informative">
<h1>Interfaces</h1>
<p>
In order to allow Verifier operation as decribed in <a href="#verifier-operations">the previous section</a>,
this
document proposes a definition of the Interfaces between the Verifier and other components.
</p>
<p>
Those interfaces MUST be independent from any framework or programming language. Interfaces shall be
implemented with standard communication protocols through web services. Usage of REST is recommended.
</p>
Depending on the party to interact and the functionality described to cover, a Verifier SHALL make use of the
following defined interfaces for his operation:
<figure id="api-functional-alignment">
<pre class="json">
+------------------------------------++------------------------------------++-----------------++-----------------+
| Holder || Governance || DID Resolver || Issuer |
+------------------------------------++------------------------------------++-----------------++-----------------+
+------------------------------------------------------------------------------------------------------------------+
|+-----------------++-----------------++-----------------++-----------------++-----------------++-----------------+|
|| || || || || || ||
|| Presentation || Data || Schema Registry || Issuer Registry || DID Resolution || Credential ||
|| Exchange || Agreement || Query || Query || || Status ||
|| || || || || || Query ||
|| || || || || || ||
|| || || || || || ||
|| API || API || API || API || API || API ||
++-----------------++------------------------------------++-----------------++-----------------++-----------------++
| 1, 2.3, 3, | 2.6, 2.7, | 2.6, 7 | 2.2 | 2.1, 2.2, | 2.3 |
| 4, 6, 7 | 5, 6 | | | 2.4, 4 | |
| |
| Verifier |
| |
+------------------------------------------------------------------------------------------------------------------+
</pre>
<figcaption style="text-align: center;">
Alignment of Interfaces with functionalities to cover
</figcaption>
</figure>
</section>
<section data-dfn-for="DID Resolution">
<h1>DID Resolution</h1>
Standard protocol and considerations for DID Resolution is being defined by a specific working group. <a
href="https://w3c-ccg.github.io/did-resolution/">See [DID-RESOLUTION] </a>.
</section>
<section data-dfn-for="Credential Status">
<h1>Credential Status</h1>
Standard protocol and considerations for querying the status of the credentials and managing their
revocation is being defined by a specific working group. <a
href="https://w3c-ccg.github.io/vc-status-rl-2020/">See [VC-STATUS-RL-2020] </a>.
</section>
<section data-dfn-for="Registries">
<h2>Registries</h2>
<p>
Registries managed by the Identity platform governance are needed to:
<ol>
<li>
Discover the credentials available on the Identity platform
</li>
<li>
Manage the format of every credential
</li>
<li>
Stablish the relation between different credentials, taken as attributes to build more complex
credentials
</li>
<li>
Define and restrict the entities enabled to assert and validate the information from the subjects
</li>
<li>
Assign different levels of trust to the identity validation processes
</li>
</ol>
</p>
<p>
Registries of Issuers and Credential Schemas MAY be separated and managed by different entities.
Multiple registries of Issuers and/or Schemas MAY be queried by a Verifier.
</p>
<p>
Verifiers MAY make use of internal private registries to complement the public registries.
Defining a protocol to merge different registries is outside the scope of this document.
</p>
<p>
Registries SHALL be publicly available and auditable. Persisting registries on DLTs is OPTIONAL but
RECOMMENDED as good practice in order to maintain neutrality.
</p>
<section data-dfn-for="Registry Query">
<h3>
Registry Query
</h3>
<p>
Registries MUST offer a web interface. REST protocol SHOULD be employed with HTTP Method GET and
JSON formatting as default.
</p>
<p>
Registries SHOULD present a unique endpoint to retrieve different entities. The entity SHOULD be
selected with either a path or a query parameter. For query parameters, the parameter name MUST be
"entity".
</p>
<p>
Entity names MUST be:
<ul>
<li>
credentialTypes
</li>
<li>
credentialGroups
</li>
<li>
authority
</li>
</ul>
</p>
<pre class="example" title="Entities on path parameters">
<pre class="http">
GET https://registry.org/api/v1/ssiregistry/credentialTypes
GET https://registry.org/api/v1/ssiregistry/credentialGroups
GET https://registry.org/api/v1/ssiregistry/authority
</pre>
</pre>
<pre class="example" title="Entities on query parameters">
<pre class="http">
GET https://registry.org/api/v1/ssiregistry?entity=credentialTypes
GET https://registry.org/api/v1/ssiregistry?entity=credentialGroups
GET https://registry.org/api/v1/ssiregistry?entity=authority
</pre>
</pre>
<h4>
Authentication
</h4>
<p>Registries SHOULD be public.</p>
<p>However, for a better adaptability to business requirements, registries MAY be authenticated.</p>
<p>Authentication SHOULD be enforced following current web service standards: on HTTP/HTTPs interfaces,
it should be handled with current standard authentication protocols, such as Basic Auth, Bearer
tokens, OAuth2.0 or OpenId Connect.</p>
</section>
<section data-dfn-for="Registry Discovery">
<h2>
Discovery
</h2>
<p>
To be defined.
</p>
<p class="ednote">
This section should be filled with discovery of registry endpoints for automatic configuration, as
well as protocols to discover other registries.
</p>
</section>
</section>
<section data-dfn-for="Schema Registry">
<h2>Schema Registry</h2>
<p>
The Schema registry satisfies the needs of managing the credentials available in the platform, with
their format and internal relations.
</p>
<p class="ednote">
This definition proposal has tried to unify several credential Catalogs usages or efforts: Gataca Catalog,
<a href="https://jolocom-lib.readthedocs.io/en/latest/interactionFlows.html#credential-issuance">Jolocom</a>
and<a href="https://identity.foundation/credential-manifest/">DIF's Credential Manifest</a>
</p>
<h3>
Data Model
</h3>
<section data-dfn-for="Credential Types">
<h3>Credential Types</h3>
<p>
Credential types represent all the types of the different available <b>monoclaim</b> verifiable
credentials; each of the types representing each an unique attribute of any credential.
</p>
<pre class="example">
Credential types represent minimal information: email, first name, last name...
</pre>
<p>The usage of monoclaim credentials is required to ensure both:
<ul>
<li>
Data minimization
</li>
<li>
Selective disclosure
</li>
</ul>
</p>
<dl>
<dt>
Id
</dt>
<dd>
Credential Types MUST have an Id mapping to the most restrictive type of the verifiable
credential. The id MUST be unique on its registry.
</dd>
<dt>
Name
</dt>
<dd>
Credential Types MUST have a short description to represent them on a human-readable way.
The name property MUST contain a map with different descriptions depending on the Locale
code.
The name MUST NOT be empty and have at least a default value.
</dd>
<dt>
Group List
</dt>
<dd>
Credential Types MUST refer the list of Credential groups where they can be
assessed. The list MUST contain 1 or more groups.
The same attribute MAY be present in more than one group, while its schema MUST be fix
on all those groups.
<pre class="example json">
An attribute credential of type first name could be found in multiple more complex credentials: passports, driver licenses, academic certificates...
</pre>
</dd>
<dt>
Schema URI
</dt>
<dd>
Credential Types SHALL provide a public URL to retrieve their schema on a
machine-readable way. The schema MUST provide the format enforced by the credential,
</dd>
<dt>
Schema
</dt>
<dd>
Credential Types MAY have their schema defined. Either the Schema or the Schema URI
properties MUST be defined to validate the credential formats.
</dd>
<dt>
Description
</dt>
<dd>
Credential Types MAY have a human readable description to allow external users to understand
the information contained on the credential and how to use it. The description MAY provide
additional information to the description present on the Credential schema.
</dd>
</dl>
<pre class="example" title="Credential Type with Schema">
<pre class="json">
{
"groupList": [ "email"],
"id": "emailCredential",
"name": {
"en": "Email"
},
"schema": "{\"title\":\"JSON Schema for monoclaim verifiable credentials of type emailCredential\",\"required\":[\"credentialSubject\",\"id\",\"issuanceDate\",\"issuer\",\"proof\",\"type\"],\"properties\":{\"credentialSubject\":{\"title\":\"Claims established about the subject defined by his DID.\",\"required\":[\"id\"],\"properties\":{\"id\":{\"title\":\"DID identifier of the subject about whom the claims have been verified\",\"default\":\"\",\"pattern\":\"^did:gatc:[A-Za-z0-9]{32}$\",\"examples\":[\"did:gatc:OWU3ZGRhOGJmYTY1ZjNlODBhZmY4MDgx\"],\"$id\":\"#/properties/credentialSubject/properties/id\",\"type\":\"string\"},\"email\":{\"title\":\"Email address owned by the subject\",\"default\":\"\",\"format\":\"email\",\"examples\":[\"[email protected]\"],\"$id\":\"#/properties/credentialSubject/properties/email\",\"type\":\"string\"}},\"$id\":\"#/properties/credentialSubject\",\"type\":\"object\"},\"credentialStatus\":{\"title\":\"Current status resource of the credential\",\"required\":[\"id\",\"type\"],\"properties\":{\"id\":{\"title\":\"Unique Identifier of the Status Information\",\"default\":\"\",\"pattern\":\"^did:gatc:[A-Za-z0-9]{32}$\",\"examples\":[\"did:gatc:OWU3ZGRhOGJmYTY1ZjNlODBhZmY4MDgx\"],\"$id\":\"#/properties/credentialSubject/properties/id\",\"type\":\"string\"},\"type\":{\"title\":\"Status presentation standard\",\"default\":\"CredentialStatusList2017\",\"enum\":[\"CredentialStatusList2017\"],\"examples\":[\"did:gatc:OWU3ZGRhOGJmYTY1ZjNlODBhZmY4MDgx\"],\"$id\":\"#/properties/credentialSubject/properties/id\",\"type\":\"string\"}},\"$id\":\"#/properties/credentialStatus\",\"type\":\"object\"},\"id\":{\"title\":\"Gataca Verifiable Credential Unique Resource Identifier\",\"default\":\"\",\"pattern\":\"^cred:gatc:[A-Za-z0-9]{32}$\",\"examples\":[\"cred:gatc:MWJmNDk2M2ZlODgwYzIwZTkyZWFjMjY1\"],\"$id\":\"#/properties/id\",\"type\":\"string\"},\"issuanceDate\":{\"title\":\"Credential first issuance date\",\"default\":\"\",\"format\":\"date-time\",\"examples\":[\"2020-05-05T13:45:54Z\"],\"$id\":\"#/properties/issuanceDate\",\"type\":\"string\"},\"issuer\":{\"title\":\"DID Identifier of the first issuer that generated this credential\",\"default\":\"\",\"pattern\":\"^did:gatc:[A-Za-z0-9]{32}$\",\"examples\":[\"did:gatc:acYseLtTEVeqF8oBhJEejbCVHJ8auVupaRuo6gw4hmXjcc77uCKqyM3imEJH\"],\"$id\":\"#/properties/issuer\",\"type\":\"string\"},\"proof\":{\"title\":\"Array of proofs from different DIDs attesting this claim\",\"items\":{\"title\":\"Verifiable Data- Proof\",\"required\":[\"created\",\"creator\",\"proofPurpose\",\"proofValue\",\"type\"],\"properties\":{\"created\":{\"title\":\"Proof creation date\",\"default\":\"\",\"format\":\"date-time\",\"examples\":[\"2020-05-05T13:45:55Z\"],\"$id\":\"#/properties/proof/items/properties/created\",\"type\":\"string\"},\"creator\":{\"title\":\"Proof Signer Key\",\"default\":\"\",\"pattern\":\"^did:gatc:[A-Za-z0-9]{32}\\\\#(.*)$\",\"examples\":[\"did:gatc:acYseLtTEVeqF8oBhJEejbCVHJ8auVupaRuo6gw4hmXjcc77uCKqyM3imEJH#keys-1\"],\"$id\":\"#/properties/proof/items/properties/creator\",\"type\":\"string\"},\"proofPurpose\":{\"title\":\"Purpose enforced by the proof\",\"default\":\"assertionMethod\",\"enum\":[\"authentication\",\"assertionMethod\",\"keyAgreement\",\"contractAgreement\",\"capabilityInvocation\",\"capabilityDelegation\"],\"examples\":[\"authentication\"],\"$id\":\"#/properties/proof/items/properties/proofPurpose\",\"type\":\"string\"},\"proofValue\":{\"title\":\"Data Signature\",\"default\":\"\",\"pattern\":\"^(.*)$\",\"examples\":[\"SuDU_pRxRud6x-LDpuiSwv0bT9tW41eJR7R9SY4SxOm5jkbnRELXxqd5BqxyRp8d1DIKHgjuwGfAI9ceqDN1DQ\"],\"$id\":\"#/properties/proof/items/properties/proofValue\",\"type\":\"string\"},\"type\":{\"title\":\"Cryptographic signing protocol\",\"default\":\"Ed25519Signature2018\",\"enum\":[\"Ed25519Signature2018\",\"RsaSignature2018\"],\"examples\":[\"Ed25519Signature2018\"],\"$id\":\"#/properties/proof/items/properties/type\",\"type\":\"string\"}},\"$id\":\"#/properties/proof/items\",\"type\":\"object\"},\"$id\":\"#/properties/proof\",\"type\":\"array\"},\"type\":{\"title\":\"Credential Types defining the schemas this credential enforces\",\"items\":{\"title\":\"Credential Type description\",\"default\":\"\",\"enum\":[\"VerifiableCredential\",\"emailCredential\"],\"examples\":[\"VerifiableCredential\"],\"$id\":\"#/properties/type/items\",\"type\":\"string\"},\"$id\":\"#/properties/type\",\"type\":\"array\"}},\"$id\":\"https://gataca.io/verifiableCredentialSchema.json#\",\"type\":\"object\",\"definitions\":{},\"$schema\":\"http://json-schema.org/draft-07/schema#\"}"
}
</pre>
</pre>
<pre class="example" title="Credential Type with Schema URI and description">
<pre class="json">
{
"groupList": [ "email"],
"id": "emailCredential",
"name": {
"en": "Email",
"es": "Email",
"fr": "Email"
},
"schemaUri": "https://schema.org/EmailCredential",
"description": "This credential contains a verified email address from the user."
}
</pre>
</pre>
</section>
<section data-dfn-for="Credential Groups">
<h3>Credential Groups</h3>
<p>
During an unique process of asserting the Subject's identity it MAY be possible to assert
several of the attributes of his identity. Thus, as multiple claims can be stablished from a
single process, the monoclaim Verifiable Credentials MUST be grouped into more complex
structures, defined as Credential Groups.
Credential Groups represent a set of monoclaim credentials bound together in order to build a
more complex credential. All those credentials MUST be considered as belonging to the same
credential, and their lifecycle managed uniquely.
</p>
<p>
Credentials should be presented however individually. To understand how credentials in groups
must be used on presentations, refer to <a href="#presentation-exchange">the following
section</a>
</p>
<pre class="example json">
Credentials Groups represent complex credentials with multiple claims: drivers license, passport, academic certificate...
</pre>
<pre class="example json">
Credentials Groups can represent also a complex credential with a single claim: email, phone number...
</pre>
<dl>
<dt>
Id
</dt>
<dd>
Credential Groups MUST have an unique identifier on the registry. The identifier SHOULD represent an
unique process of identity-assertion, generating a complex multi-claim credential, from which one or
more attributes of a subject identity can be extracted.
</dd>
<dt>
Name
</dt>
<dd>
Credential Groups MUST have a short description to represent them on a human-readable way, as a
title of the credential.
The name property MUST contain a map with different descriptions depending on the Locale
code.
The name MUST NOT be empty and have at least a default value.
</dd>
<dt>
Display
</dt>
<dd>
Credential groups represent complex credentials, human-readable and understandable for users. In
order to allow customization or representation, they MUST contain information about how to represent
them.
<dl>
<dt>
Main Claim
</dt>
<dd>
The main claim MUST represent the Credential Type most representative of the whole
credential group to allow the presentation of its value to the user as a title.
<pre class="example json">
For a academic certificate credential, the academic degree obtained could be the main claim.
</pre>
</dd>
<dt>
Secondary Claim
</dt>
<dd>
The secondary claim MAY represent another Credential Type very representative of the
credential group, to allow the presentation of its value to the user as a subtitle.
<pre class="example json">
For a academic certificate credential, the academic institution could be a secondary claim.
</pre>
</dd>
<dt>
Logo
</dt>
<dd>
The logo property MAY allow identifying a credential with a fixed logo. The logo can be
defined by its URI, its content base64 codified or its svg definition.
<dl>
<dt>
URI
</dt>
<dt>
Base64
</dt>
<dt>
Svg
</dt>
</dl>
</dd>
<dt>
Background
</dt>
<dd>
The background property is OPTIONAL. It MAY be used to enforce a standard representation of
the credential on different Wallets and User Agents.
<dl>
<dt>
Color
</dt>
<dt>
URI
</dt>
<dt>
Base64
</dt>
<dt>
Svg
</dt>
</dl>
</dd>
<dt>
Text
</dt>
<dd>
The text property is OPTIONAL. It MAY be used to define the presentation format of the text
describing the credential.
<dl>
<dt>
Color
</dt>
<dt>
Font Family
</dt>
</dl>
</dd>
</dl>
</dd>
<dt>
Description
</dt>
<dd>
Credential Types MAY have a human readable description to allow external users to understand
the information contained on the credential and how to use it. The description MAY provide
additional information to the description present on the Credential schema.
</dd>
</dl>
<pre class="example" title="Credential Group example">
<pre class="json">
{
"id": "university",
"name": {
"en": "University Qualification",
"es": "Título Universitario"
},
"description": "This credential group asserts the obtention of an academic degree by a valid academical institution.",
"display":{
"mainClaim": "qualificationCredential",
"secondaryClaim": "academicInstitutionCredential",
"logo":{
"uri":"https://www.svgrepo.com/show/293955/university.svg"
},
"background":{
"color":"#1025a0"
},
"text":{
"color":"#ffffff"
}
}
}
</pre>
</pre>
</section>
</section>
<section data-dfn-for="Issuer Registry">
<h2>Issuer Registry</h2>
<p>
The issuer registry MUST contain all the different institutions that have been attested as valid verifiers
of subject's identities.
</p>
<p class="ednote">
There doesn't seem to be much standarization effort on defining different issuers.
</p>
<h3>Trust levels</h3>
<p>
Governance SHOULD assign different trust levels to the entity asserting the validity of the subject
credentials.
</p>
<p>
Three different trust levels have been defined:
<table>
<tr>
<th>
Level
</th>
<th>Indication</th>
<th>Meaning</th>
</tr>
<tr>
<td>
0
</th>
<th>Self-attested</th>
<th>The credential is asserted by the subject self. No external entity has validated the data.</th>
</tr>
<tr>
<td>
1
</th>
<th>Validated</th>
<th>The credential is validated by an external entity which has been deemed able to validate that type
of credential. The entity is not the issuer nor of the source of the data verified.</th>
</tr>
<tr>
<td>
2
</th>
<th>Issued</th>
<th>The credential is validated by the same entity which is the owner or the source of the data
verified.</th>
</tr>
</table>
<pre class="example json" title="Example of Issuer Levels">
For a credential of type phone:
* Level 0: The subject could assert his phone number
* Level 1: A validator could verify the possesion of the phone using an OTP.
* Level 2: His phone company could assert the possesion of the phone number associated.
</pre>
<p class="ednote">
eIDas assigns 4 different levels of trust to the data. This model offers a simpler and different approach,
regarding the entity validating the data; nor the validation process itself.
</p>
<p>
A same entity could have different Trust levels on the assertion of different credentials
</p>
<pre class="example json" title="Example of Issuer Levels for the same Issuer">
A bank entity could be:
* Level 1 validator of national documents
* Level 2 validator of IBANs of their bank
</pre>
<p>
The trust level of a credential process should apply to credential groups, as the process of asserting
identity claims usually applies to complex credentials with more than one claim.
</p>
</p>
<h3>
Data Model
</h3>
<section data-dfn-for="Authority">
<h3>Authority</h3>
<dl>
<dt>
Id
</dt>
<dd>
Authorities MUST be represented by their unique DID.
</dd>
<dt>
Name
</dt>
<dd>
Authorities MUST have a short description to represent them on a human-readable way as a title.
The name property MUST contain a map with different descriptions depending on the Locale
code.
The name MUST NOT be empty and have at least a default value.
</dd>
<dt>
Display
</dt>
<dd>
Authorities MAY contain additional display information to provide compliance with their digital
image guidelines.
<dl>
<dt>
Logo
</dt>
<dd>
The logo property MAY allow identifying a credential with a fixed logo. The logo can be
defined by its URI, its content base64 codified or its svg definition.
<dl>
<dt>
URI
</dt>
<dt>
Base64
</dt>
<dt>
Svg
</dt>
</dl>
</dd>
<dt>
Background
</dt>
<dd>
The background property is OPTIONAL. It MAY be used to enforce a standard representation of
the credential on different Wallets and User Agents.
<dl>
<dt>
Color
</dt>
<dt>
URI
</dt>
<dt>
Base64
</dt>
<dt>
Svg
</dt>
</dl>
</dd>
<dt>
Text
</dt>
<dd>
The text property is OPTIONAL. It MAY be used to define the presentation format of the text
describing the credential.
<dl>
<dt>
Color
</dt>
<dt>
Font Family
</dt>
</dl>
</dd>
</dl>
</dd>
<dt>
Credential List
</dt>
<dd>
Every authority MUST have a list of the different groups of credentials whose claims it can
validate.
<dl>
<dt>
Group
</dt>
<dd>
Id of the Credential Group to validate
</dd>
<dt>
Trust Level
</dt>
<dd>
Designated trust level for that authority to that group. The trust level for any authority
MUST be either 1 or 2.
</dd>
</dl>
</dd>
</dl>
<pre class="example" title="Example of authority">
<pre class="json">
{
"id": "did:gatc:47bad539a8371e57ebb6370e6ac93bc2dddfa2f2f8a92c632de1e88ce166601f",
"name": {
"en": "Issuer Demo",
"es": "Emisor de prueba"
},
"display":{
"logo":{
"uri":"https://www.svgrepo.com/show/293955/university.svg"
},
"background":{
"color":"#1025a0"
},
"text":{
"color":"#ffffff"
}
},
"credentialList":[
{
"group": "phone",
"trustLevel": 1
},
{
"group": "email",
"trustLevel": 1
}
]
}
</pre>
</pre>
</section>
</section>
<section data-dfn-for="Presentation Exchange" class="informative">
<h2>Presentation Exchange</h2>
<p>
The presentation exchange is the protocol of communication between the Verifier and the Holder to retrieve
Verifiable Credentials.
</p>
<p>
The presentation exchange consists on a two step process:
<ol>
<li>
The Holder retrieves a Presentation Request from the verifier.
</li>
<li>
The Holder provides a Presentation Response, containing one or more verifiable presentations to the
verifier.
</li>
</ol>
</p>
<h3>
Obtaining the Presentation Request
</h3>
<p>
A Presentation Exchange takes place when a Service Provider, connected to a Verifier, needs to retrieve
Verifiable Credentials from an end user. The user subject MAY store his credentials on a wallet Holder,
either on the same or a different User-Agent and device than the Service Provider.
</p>
<p>
To access the Holder on any device, the Verifier MUST offer the user a deep link to retrieve the verifiable
presentation.
<section data-dfn-for="Deep Link" class="informative">
<h3>DeepLink</h3>
<p>
The deep link MUST use an unique protocol definition: <b>did://</b>. Wallets on different user-agents
MAY register to listen to that protocol. The protocol MUST NOT be the same as other existing protocols,
even authentication protocols such as <b>openid://</b>, as presentation exchanges cover several use
cases apart from authentication.
</p>
<h4>Deep Link format</h4>
<p>
<code class="http">
did://presentation-exchange?uri=""&jwt=""
</code>
</p>
For presentation exchanges, the deep link should have the following properties:
<dl>
<dt>
Protocol
</dt>
<dd>
Permanent: <b>did://</b>
</dd>
<dt>
Action
</dt>
<dd>
Permanent: <b>presentation-exchange</b>
</dd>
<dt>
Parameters. Only one of the two options is required
</dt>
<dd>
<dl>
<dt>
uri
</dt>
<dd>
OPTIONAL: Base64URL encoding of the URI of the resource to retrieve the presentation request
</dd>
<dt>
jwt
</dt>
<dd>
OPTIONAL: JWT containing the presentation request on JWT format
</dd>
</dl>
</dd>
</dl>
<pre class="example" title="Presentation exchange with URI">
did://presentation-exchange?uri=aHR0cHM6Ly9jb25uZWN0LmdhdGFjYS5pbzo5MDkwL2FwaS92MS9zZXNzaW9ucy9Ea3N2QTB6bzFDVDR2SjNqbEZKcGMxRjFxejI1OEd1dg
</pre>
<p class="issue">
Consider delegating services to allow static deep links
</p>
<p class="ednote">
The format of this deep link is for the moment a suggestion. The definition of the deep link protocol
may be outside the scope of this document.
</p>
</section>
In order to obtain the presentation request, the Verifier should detect the device of the subject compared to