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<!DOCTYPE html>
<html>
<head>
<title>Data Integrity EdDSA Cryptosuites v1.0</title>
<meta http-equiv="Content-Type" content="text/html;charset=utf-8" />
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title: "Multicodec",
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title: "Taming the many EdDSAs",
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authors: ["Jacqueline Brendel", "Cas Cremers", "Dennis Jackson", "Mang Zhao"],
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<body>
<section id="abstract">
<p>
This specification describes a Data Integrity cryptographic suite for use when
creating or verifying a digital signature using the the Ed25519 instantiation
of the Edwards-Curve Digital Signature Algorithm (EdDSA).
</p>
</section>
<section id="sotd">
<p>
The Working Group is actively seeking implementation feedback for this
specification. In order to exit the Candidate Recommendation phase, the
Working Group has set the requirement of at least two independent
implementations for each mandatory feature in the specification. For details
on the conformance testing process, see the test suites listed in the
<a href="https://w3c.github.io/vc-data-integrity/implementations/">
implementation report</a>.
</p>
</section>
<section>
<h2>Introduction</h2>
<p>
This specification defines a cryptographic suite for the purpose of creating,
verifying proofs for Ed25519 EdDSA signatures in conformance with the
Data Integrity [[VC-DATA-INTEGRITY]] specification. The approach is
accepted by the U.S. National Institute of Standards in the latest [[FIPS-186-5]]
publication and meets U.S. Federal Information Processing requirements when
using cryptography to secure digital information.
</p>
<p>
The suites described in this specification use the RDF Dataset Canonicalization
Algorithm [[RDF-CANON]] or the JSON Canonicalization Scheme [[RFC8785]] to
transform an input document into its canonical form. The canonical
representation is then hashed and signed with a detached signature algorithm.
</p>
<section id="terminology">
<h3>Terminology</h3>
<p>
Terminology used throughout this document is defined in the
<a data-cite="VC-DATA-INTEGRITY#terminology">Terminology</a> section of the
[[[VC-DATA-INTEGRITY]]] specification.
</p>
</section>
<section id="conformance">
<p>
A <dfn>conforming proof</dfn> is any concrete expression of the data model
that complies with the normative statements in this specification. Specifically,
all relevant normative statements in Sections
[[[#data-model]]] and [[[#algorithms]]]
of this document MUST be enforced.
</p>
<p>
A <dfn class="lint-ignore">conforming processor</dfn> is any algorithm realized
as software and/or hardware that generates or consumes a
<a>conforming proof</a>. Conforming processors MUST produce errors when
non-conforming documents are consumed.
</p>
<p>
This document contains examples of JSON and JSON-LD data. Some of these examples
are invalid JSON, as they include features such as inline comments (`//`)
explaining certain portions and ellipses (`...`) indicating the omission of
information that is irrelevant to the example. These parts would have to be
removed in order to treat the examples as valid JSON or JSON-LD.
</p>
</section>
</section>
<section>
<h2>Data Model</h2>
<p>
The following sections outline the data model that is used by this specification
to express verification methods, such as cryptographic public keys, and
data integrity proofs, such as digital signatures.
</p>
<section>
<h3>Verification Methods</h3>
<p>
This cryptographic suite is used to verify Data Integrity Proofs
[[VC-DATA-INTEGRITY]] produced using Edwards Curve cryptographic key material.
The encoding formats for those key types are provided in this section. Lossless
cryptographic key transformation processes that result in equivalent
cryptographic key material MAY be used for the processing of digital
signatures.
</p>
<section>
<h4>Multikey</h4>
<p>
The <a data-cite="controller-document#multikey">Multikey format</a>, defined in
[[[controller-document]]], is used to express public keys for the cryptographic
suites defined in this specification.
</p>
<p>
The `publicKeyMultibase` value of the verification method MUST start with the
base-58-btc prefix (`z`), as defined in the
<a data-cite="controller-document#multibase-0">Multibase section</a> of
[[[controller-document]]]. A Multibase-encoded Multikey value follows, which MUST
consist of a binary value that starts with the two-byte prefix `0xed01`, which
is the Multikey header for an Ed25519 public key, followed by the 32-byte public
key data, all of which is then encoded using base-58-btc. Any other encoding
MUST NOT be allowed.
</p>
<p class="advisement">
Developers are advised to not accidentally publish a representation of a private
key. Implementations of this specification will raise errors if they encounter a
Multikey prefix value other than `0xed01` in a `publicKeyMultibase` value.
</p>
<pre class="example nohighlight"
title="An Ed25519 public key encoded as a Multikey">
{
"id": "https://example.com/issuer/123#key-0",
"type": "Multikey",
"controller": "https://example.com/issuer/123",
"publicKeyMultibase": "z6Mkf5rGMoatrSj1f4CyvuHBeXJELe9RPdzo2PKGNCKVtZxP"
}
</pre>
<pre class="example nohighlight" title="An Ed25519 public key encoded as a
Multikey in a controller document">
{
"@context": [
"https://www.w3.org/ns/did/v1",
"https://w3id.org/security/multikey/v1"
],
"id": "did:example:123",
"verificationMethod": [{
"id": "did:example:123#key-0",
"type": "Multikey",
"controller": "did:example:123",
"publicKeyMultibase": "z6Mkf5rGMoatrSj1f4CyvuHBeXJELe9RPdzo2PKGNCKVtZxP"
}],
"authentication": [
"did:example:123#key-0"
],
"assertionMethod": [
"did:example:123#key-0"
],
"capabilityDelegation": [
"did:example:123#key-0"
],
"capabilityInvocation": [
"did:example:123#key-0"
]
}
</pre>
<p>
The `secretKeyMultibase` property represents a Multibase-encoded Multikey
expression of an Ed25519 secret key (sometimes also referred to as a private
key). The value starts with the two-byte prefix `0x8026`,
followed by the 32-byte Ed25519 secret key data. The combined
34-byte value is then base58-btc encoded and `z` is added as the prefix on the
encoded value.
</p>
<p class="advisement">
Developers are advised to prevent accidental publication of a representation of
a secret key, and to not export the `secretKeyMultibase` property by default,
when serializing key pairs to Multikey.
</p>
</section>
</section>
<section>
<h3>Proof Representations</h3>
<p>
This section details the proof representation formats that are defined by
this specification.
</p>
<section>
<h4>DataIntegrityProof</h4>
<p>
A proof contains the attributes specified in the
<a href="https://www.w3.org/TR/vc-data-integrity/#proofs">Proofs section</a>
of [[VC-DATA-INTEGRITY]] with the following restrictions.
</p>
<p>
The `type` property MUST be `DataIntegrityProof`.
</p>
<p>
The `cryptosuite` property of the proof MUST be `eddsa-rdfc-2022` or `eddsa-jcs-2022`.
</p>
<p>
The `proofValue` property of the proof MUST be a detached EdDSA signature
produced according to [[RFC8032]], encoded using the base-58-btc header and
alphabet as described in the
<a data-cite="controller-document#multibase-0">Multibase section</a> of
[[[controller-document]]].
</p>
<pre class="example nohighlight"
title="An Ed25519 digital signature expressed as a
DataIntegrityProof">
{
"@context": [
{"myWebsite": "https://vocabulary.example/myWebsite"},
"https://www.w3.org/ns/credentials/v2"
],
"myWebsite": "https://hello.world.example/",
"proof": {
"type": "DataIntegrityProof",
"cryptosuite": "eddsa-rdfc-2022",
"created": "2023-02-24T23:36:38Z",
"verificationMethod": "https://vc.example/issuers/5678#z6MkrJVnaZkeFzdQyMZu1
cgjg7k1pZZ6pvBQ7XJPt4swbTQ2",
"proofPurpose": "assertionMethod",
"proofValue": "z5C5b1uzYJN6pDR3aWgAqUMoSB1JY29epA74qyjaie9qh4okm9DZP6y77eTNq
5NfYyMwNu9bpQQWUHKH5zAmEtszK"
}
}
</pre>
</section>
</section>
</section>
<section>
<h2>Algorithms</h2>
<p>
The following section describes multiple Data Integrity cryptographic suites
that use the Edwards-Curve Digital Signature Algorithm.
</p>
<section>
<h3>Instantiate Cryptosuite</h3>
<p>
This algorithm is used to configure a cryptographic suite to be used by the
<a data-cite="VC-DATA-INTEGRITY#add-proof">Add Proof</a> and
<a data-cite="VC-DATA-INTEGRITY#verify-proof">Verify Proof</a>
functions in [[[VC-DATA-INTEGRITY]]]. The algorithm takes an options object
([=map=] |options|) as input and returns a [=data integrity cryptographic suite
instance|cryptosuite instance=] ([=struct=] |cryptosuite|).
</p>
<ol class="algorithm">
<li>
Initialize |cryptosuite| to an empty [=struct=].
</li>
<li>
If |options|.|type| does not equal `DataIntegrityProof`, return |cryptosuite|.
</li>
<li>
If |options|.|cryptosuite| is `eddsa-rdfc-2022`:
<ol class="algorithm">
<li>
Set |cryptosuite|.|createProof| to the algorithm in Section
[[[#create-proof-eddsa-rdfc-2022]]].
</li>
<li>
Set |cryptosuite|.|verifyProof| to the algorithm in Section
[[[#verify-proof-eddsa-rdfc-2022]]].
</li>
</ol>
</li>
<li>
If |options|.|cryptosuite| is `eddsa-jcs-2022`:
<ol class="algorithm">
<li>
Set |cryptosuite|.|createProof| to the algorithm in Section
[[[#create-proof-eddsa-jcs-2022]]].
</li>
<li>
Set |cryptosuite|.|verifyProof| to the algorithm in Section
[[[#verify-proof-eddsa-jcs-2022]]].
</li>
</ol>
</li>
<li>
Return |cryptosuite|.
</li>
</ol>
</section>
<section>
<h3>eddsa-rdfc-2022</h3>
<p>
The `eddsa-rdfc-2022` cryptographic suite takes an input document, canonicalizes
the document using the RDF Dataset Canonicalization algorithm [[RDF-CANON]], and then
cryptographically hashes and signs the output
resulting in the production of a data integrity proof. The algorithms in this
section also include the verification of such a data integrity proof.
</p>
<p class="advisement">
When the RDF Dataset Canonicalization Algorithm [[RDF-CANON]] is used,
implementations will detect <a data-cite="RDF-CANON#dataset-poisoning">
dataset poisoning</a> by default, and abort processing upon such detection.
</p>
<section>
<h4>Create Proof (eddsa-rdfc-2022)</h4>
<p>
The following algorithm specifies how to create a [=data integrity proof=] given
an <a>unsecured data document</a>. Required inputs are an
<a>unsecured data document</a> ([=map=] |unsecuredDocument|), and a set of proof
options ([=map=] |options|). A [=data integrity proof=] ([=map=]), or an error,
is produced as output.
</p>
<ol class="algorithm">
<li>
Let |proof| be a clone of the proof options, |options|.
</li>
<li>
Let |proofConfig| be the result of running the algorithm in
Section [[[#proof-configuration-eddsa-rdfc-2022]]] with
|options| passed as a parameter.
</li>
<li>
Let |transformedData| be the result of running the algorithm in Section <a
href="#transformation-eddsa-rdfc-2022"></a> with |unsecuredDocument|,
|proofConfig|, and |options| passed as parameters.
</li>
<li>
Let |hashData| be the result of running the algorithm in Section
[[[#hashing-eddsa-rdfc-2022]]] with |transformedData| and |proofConfig|
passed as a parameters.
</li>
<li>
Let |proofBytes| be the result of running the algorithm in Section
[[[#proof-serialization-eddsa-rdfc-2022]]] with |hashData| and
|options| passed as parameters.
</li>
<li>
Let |proof|.|proofValue| be a <a data-cite="controller-document#multibase-0">
base58-btc-encoded Multibase value</a> of the |proofBytes|.
</li>
<li>
Return |proof| as the [=data integrity proof=].
</li>
</ol>
</section>
<section>
<h4>Verify Proof (eddsa-rdfc-2022)</h4>
<p>
The following algorithm specifies how to verify a [=data integrity proof=] given
an <a>secured data document</a>. Required inputs are an
<a>secured data document</a> ([=map=] |securedDocument|). This algorithm returns
a <dfn>verification result</dfn>, which is a [=struct=] whose
[=struct/items=] are:
</p>
<dl>
<dt><dfn data-dfn-for="verification result">verified</dfn></dt>
<dd>`true` or `false`</dd>
<dt><dfn data-dfn-for="verification result">verifiedDocument</dfn></dt>
<dd>
if [=verification result/verified=] is `false`, <a data-cite="INFRA#nulls">Null</a>;
otherwise, an [=unsecured data document=]
</dd>
</dl>
<ol class="algorithm">
<li>
Let |unsecuredDocument| be a copy of |securedDocument| with
the `proof` value removed.
</li>
<li>
Let |proofOptions| be the result of a copy of |securedDocument|.|proof| with `proofValue`
removed.
</li>
<li>
Let |proofBytes| be the
<a data-cite="controller-document#multibase-0">Multibase decoded base58-btc
value</a> in |securedDocument|.|proof|.|proofValue|.
</li>
<li>
Let |transformedData| be the result of running the algorithm in Section <a
href="#transformation-eddsa-rdfc-2022"></a> with |unsecuredDocument| and
|proofOptions| passed as parameters.
</li>
<li>
Let |proofConfig| be the result of running the algorithm in Section <a
href="#proof-configuration-eddsa-rdfc-2022"></a> with |unsecuredDocument| and
|proofOptions| passed as parameters.
</li>
<li>
Let |hashData| be the result of running the algorithm in Section
[[[#hashing-eddsa-rdfc-2022]]] with |transformedData| and |proofConfig|
passed as a parameters.
</li>
<li>
Let |verified:boolean| be the result of running the algorithm in Section
[[[#proof-verification-eddsa-rdfc-2022]]] algorithm on |hashData|,
|proofBytes|, and |proofConfig|.
</li>
<li>
Return a [=verification result=] with [=struct/items=]:
<dl data-link-for="verification result">
<dt>[=verified=]</dt>
<dd>|verified|</dd>
<dt>[=verifiedDocument=]</dt>
<dd>
if |verified| is `true`, |unsecuredDocument|;
otherwise, <a data-cite="INFRA#nulls">Null</a></dd>
</dl>
</li>
</ol>
</section>
<section>
<h4>Transformation (eddsa-rdfc-2022)</h4>
<p>
The following algorithm specifies how to transform an unsecured input document
into a transformed document that is ready to be provided as input to the
hashing algorithm in Section [[[#hashing-eddsa-rdfc-2022]]].
</p>
<p>
Required inputs to this algorithm are an
<a data-cite="vc-data-integrity#dfn-unsecured-data-document">
unsecured data document</a> (`unsecuredDocument`) and
transformation options (`options`). The
transformation options MUST contain a type identifier for the
<a data-cite="vc-data-integrity#dfn-cryptosuite">
cryptographic suite</a> (`type`) and a cryptosuite
identifier (`cryptosuite`). A <em>transformed data document</em> is
produced as output. Whenever this algorithm encodes strings, it MUST use UTF-8
encoding.
</p>
<ol class="algorithm">
<li>
If `options`.`type` is not set to the string
`DataIntegrityProof` and `options`.`cryptosuite` is not
set to the string `eddsa-rdfc-2022`,
an error MUST be raised that SHOULD convey an error type of
<a data-cite="VC-DATA-INTEGRITY#PROOF_TRANSFORMATION_ERROR">PROOF_TRANSFORMATION_ERROR</a>.
</li>
<li>
Let |canonicalDocument| be the result of converting |unsecuredDocument|
<a data-cite="JSON-LD11-API#deserialize-json-ld-to-rdf-algorithm">
to RDF statements</a>, applying the RDF Dataset Canonicalization
Algorithm [[RDF-CANON]] to the result, and then serializing the result to
[[N-QUADS]].
</li>
<li>
Return `canonicalDocument` as the <em>transformed data document</em>.
</li>
</ol>
</section>
<section>
<h4>Hashing (eddsa-rdfc-2022)</h4>
<p>
The following algorithm specifies how to cryptographically hash a
<em>transformed data document</em> and <em>proof configuration</em>
into cryptographic hash data that is ready to be provided as input to the
algorithms in Section [[[#proof-serialization-eddsa-rdfc-2022]]] or
Section [[[#proof-verification-eddsa-rdfc-2022]]].
</p>
<p>
The required inputs to this algorithm are a <em>transformed data document</em>
(`transformedDocument`) and <em>canonical proof configuration</em>
(`canonicalProofConfig`). A single <em>hash data</em> value represented as
series of bytes is produced as output.
</p>
<ol class="algorithm">
<li>
Let `proofConfigHash` be the result of applying the
SHA-256 (SHA-2 with 256-bit output) cryptographic hashing algorithm [[RFC6234]]
to the `canonicalProofConfig`. `proofConfigHash` will be
exactly 32 bytes in size.
</li>
<li>
Let `transformedDocumentHash` be the result of applying the
SHA-256 (SHA-2 with 256-bit output) cryptographic hashing algorithm [[RFC6234]]
to the `transformedDocument`. `transformedDocumentHash` will
be exactly 32 bytes in size.
</li>
<li>
Let `hashData` be the result of concatenating `proofConfigHash`
(the first hash produced above) followed by `transformedDocumentHash`
(the second hash produced above).
</li>
<li>
Return `hashData` as the <em>hash data</em>.
</li>
</ol>
</section>
<section>
<h4>Proof Configuration (eddsa-rdfc-2022)</h4>
<p>
The following algorithm specifies how to generate a
<em>proof configuration</em> from a set of <em>proof options</em>
that is used as input to the <a href="#hashing-eddsa-rdfc-2022">proof hashing algorithm</a>.
</p>
<p>
The required inputs to this algorithm are the <em>document</em>
(|unsecuredDocument|) and the <em>proof options</em>
(`options`). The <em>proof options</em> MUST contain a type identifier
for the
<a data-cite="vc-data-integrity#dfn-cryptosuite">
cryptographic suite</a> (`type`) and MUST contain a cryptosuite
identifier (`cryptosuite`). A <em>proof configuration</em>
object is produced as output.
</p>
<ol class="algorithm">
<li>
Let |proofConfig| be a clone of the |options| object.
</li>
<li>
If |proofConfig|.|type| is not set to `DataIntegrityProof` and/or
|proofConfig|.|cryptosuite| is not set to `eddsa-rdfc-2022`, an
error MUST be raised and SHOULD convey an error type of
<a data-cite="VC-DATA-INTEGRITY#PROOF_GENERATION_ERROR">PROOF_GENERATION_ERROR</a>.
</li>
<li>
If |proofConfig|.|created| is present and set to a value that is not a
valid [[XMLSCHEMA11-2]] datetime, an error MUST be
raised and SHOULD convey an error type of
<a data-cite="VC-DATA-INTEGRITY#PROOF_GENERATION_ERROR">PROOF_GENERATION_ERROR</a>.
</li>
<li>
Set |proofConfig|.`@context `to
|unsecuredDocument|.<var>@context</var>.
</li>
<li>
Let |canonicalProofConfig| be the result of applying the
RDF Dataset Canonicalization Algorithm
[[RDF-CANON]] to the |proofConfig|.
</li>
<li>
Return |canonicalProofConfig|.
</li>
</ol>
</section>
<section>
<h4>Proof Serialization (eddsa-rdfc-2022)</h4>
<p>
The following algorithm specifies how to serialize a digital signature from
a set of cryptographic hash data. This
algorithm is designed to be used in conjunction with the algorithms defined
in the Data Integrity [[VC-DATA-INTEGRITY]] specification,
<a data-cite="vc-data-integrity#algorithms">
Section 4: Algorithms</a>. Required inputs are
cryptographic hash data (`hashData`) and
<em>proof options</em> (`options`). The
<em>proof options</em> MUST contain a type identifier for the
<a data-cite="vc-data-integrity#dfn-cryptosuite">
cryptographic suite</a> (`type`) and MAY contain a cryptosuite
identifier (`cryptosuite`). A single <em>digital proof</em> value
represented as series of bytes is produced as output.
</p>
<ol class="algorithm">
<li>
Let `privateKeyBytes` be the result of retrieving the
private key bytes associated with the
`options`.`verificationMethod` value as described in the
Data Integrity [[VC-DATA-INTEGRITY]] specification,
<a data-cite="vc-data-integrity#processing-model">
Section 4.1: Processing Model</a>.
</li>
<li>
Let `proofBytes` be the result of applying the Edwards-Curve Digital
Signature Algorithm (EdDSA) [[RFC8032]], using the `Ed25519` variant
(Pure EdDSA), with `hashData` as the data to be signed using
the private key specified by `privateKeyBytes`.
`proofBytes` will be exactly 64 bytes in size.
</li>
<li>
Return `proofBytes` as the <em>digital proof</em>.
</li>
</ol>
</section>
<section>
<h4>Proof Verification (eddsa-rdfc-2022)</h4>
<p>
The following algorithm specifies how to verify a digital signature from
a set of cryptographic hash data. This
algorithm is designed to be used in conjunction with the algorithms defined
in the Data Integrity [[VC-DATA-INTEGRITY]] specification,
<a data-cite="vc-data-integrity#algorithms">
Section 4: Algorithms</a>. Required inputs are
cryptographic hash data (`hashData`),
a digital signature (`proofBytes`) and
proof options (`options`). A <em>verification result</em>
represented as a boolean value is produced as output.
</p>
<ol class="algorithm">
<li>
Let `publicKeyBytes` be the result of retrieving the
public key bytes associated with the
`options`.`verificationMethod` value as described in the
[[[controller-document]]] specification,
<a data-cite="controller-document#retrieve-verification-method">
Section 3.3: Retrieve Verification Method</a>.
</li>
<li>
Let `verificationResult` be the result of applying the verification
algorithm for the Edwards-Curve Digital Signature Algorithm (EdDSA)
[[RFC8032]], using the `Ed25519` variant (Pure EdDSA),
with `hashData` as the data to be verified against the
`proofBytes` using the public key specified by
`publicKeyBytes`.
</li>
<li>
Return `verificationResult` as the <em>verification result</em>.
</li>
</ol>
</section>
</section>
<section>
<h3>eddsa-jcs-2022</h3>
<p>
The `eddsa-jcs-2022` cryptographic suite takes an input document, canonicalizes
the document using the JSON Canonicalization Scheme [[RFC8785]], and then
cryptographically hashes and signs the output resulting in the production of a
data integrity proof.
</p>
<section>
<h4>Create Proof (eddsa-jcs-2022)</h4>
<p>
The following algorithm specifies how to create a [=data integrity proof=] given
an <a>unsecured data document</a>. Required inputs are an
<a>unsecured data document</a> ([=map=] |unsecuredDocument|), and a set of proof
options ([=map=] |options|). A [=data integrity proof=] ([=map=]), or an error,
is produced as output.
</p>
<ol class="algorithm">
<li>
Let |proof| be a clone of the proof options, |options|.
</li>
<li>
If `unsecuredDocument`.<var>@context</var> is present,
set `proof`.<var>@context</var> to
`unsecuredDocument`.<var>@context</var>.
</li>
<li>
Let |proofConfig| be the result of running the algorithm in
Section [[[#proof-configuration-eddsa-jcs-2022]]] with
|proof| passed as the <em>proof options</em> parameter.
</li>
<li>
Let |transformedData| be the result of running the algorithm in Section
[[[#transformation-eddsa-jcs-2022]]] with |unsecuredDocument|
and |options| passed as parameters.
</li>
<li>
Let |hashData| be the result of running the algorithm in Section
[[[#hashing-eddsa-jcs-2022]]] with |transformedData| and |proofConfig|
passed as a parameters.
</li>
<li>
Let |proofBytes| be the result of running the algorithm in Section
[[[#proof-serialization-eddsa-jcs-2022]]] with |hashData| and
|options| passed as parameters.
</li>
<li>
Let |proof|.|proofValue| be a <a data-cite="controller-document#multibase-0">
base58-btc-encoded Multibase value</a> of the |proofBytes|.
</li>
<li>
Return |proof| as the [=data integrity proof=].
</li>
</ol>
</section>
<section>
<h4>Verify Proof (eddsa-jcs-2022)</h4>
<p>
The following algorithm specifies how to verify a [=data integrity proof=] given
an <a>secured data document</a>. Required inputs are an
<a>secured data document</a> ([=map=] |securedDocument|). This algorithm returns
a [=verification result=], which is a [=struct=] whose [=struct/items=] are:
</p>
<dl>
<dt>[=verification result/verified=]</dt>
<dd>`true` or `false`</dd>
<dt>[=verification result/verifiedDocument=]</dt>
<dd>
if [=verification result/verified=] is `true`, an [=unsecured data document=];
otherwise <a data-cite="INFRA#nulls">Null</a>
</dd>
</dl>
<ol class="algorithm">
<li>
Let |unsecuredDocument| be a copy of |securedDocument| with the `proof` value
removed.
</li>
<li>
Let |proofOptions| be the result of a copy of |securedDocument|.|proof| with
`proofValue` removed.
</li>
<li>
Let |proofBytes| be the
<a data-cite="controller-document#multibase-0">Multibase decoded base58-btc
value</a> in |securedDocument|.|proof|.|proofValue|.
</li>
<li>
If |proofOptions|.<var>@context</var> exists:
<ol class="algorithm">
<li>
Check that the |securedDocument|.<var>@context</var> starts with all values
contained in the |proofOptions|.<var>@context</var> in the same order.
Otherwise, set |verified| to `false` and skip to the last step.
</li>
<li>
Set |unsecuredDocument|.<var>@context</var> equal to
|proofOptions|.<var>@context</var>.
</li>
</ol>
</li>
<li>
Let |transformedData| be the result of running the algorithm in Section
[[[#transformation-eddsa-jcs-2022]]] with |unsecuredDocument| and
|proofOptions| passed as parameters.
</li>
<li>
Let |proofConfig| be the result of running the algorithm in Section
[[[#proof-configuration-eddsa-jcs-2022]]] with |proofOptions| passed
as the parameter.
</li>
<li>
Let |hashData| be the result of running the algorithm in Section
[[[#hashing-eddsa-jcs-2022]]] with |transformedData| and |proofConfig| passed as
a parameters.
</li>
<li>
Let |verified:boolean| be the result of running the algorithm in Section
[[[#proof-verification-eddsa-jcs-2022]]] on |hashData|, |proofBytes|,
and |proofConfig|.
</li>
<li>
Return a [=verification result=] with [=struct/items=]:
<dl data-link-for="verification result">
<dt>[=verified=]</dt>
<dd>|verified|</dd>
<dt>[=verifiedDocument=]</dt>
<dd>
if |verified| is `true`, |unsecuredDocument|;
otherwise, <a data-cite="INFRA#nulls">Null</a></dd>
</dl>
</li>
</ol>
</section>
<section>
<h4>Transformation (eddsa-jcs-2022)</h4>
<p>
The following algorithm specifies how to transform an unsecured input document
into a transformed document that is ready to be provided as input to the
hashing algorithm in Section [[[#hashing-eddsa-jcs-2022]]].
</p>
<p>
Required inputs to this algorithm are an
<a data-cite="vc-data-integrity#dfn-unsecured-data-document">
unsecured data document</a> (`unsecuredDocument`) and
transformation options (`options`). The
transformation options MUST contain a type identifier for the
<a data-cite="vc-data-integrity#dfn-cryptosuite">
cryptographic suite</a> (`type`) and a cryptosuite
identifier (`cryptosuite`). A <em>transformed data document</em> is
produced as output. Whenever this algorithm encodes strings, it MUST use UTF-8
encoding.
</p>
<ol class="algorithm">
<li>
If `options`.`type` is not set to the string
`DataIntegrityProof` and `options`.`cryptosuite` is not
set to the string `eddsa-jcs-2022`,
an error MUST be raised that SHOULD convey an error type of
<a data-cite="VC-DATA-INTEGRITY#PROOF_VERIFICATION_ERROR">PROOF_VERIFICATION_ERROR</a>.
</li>
<li>
Let `canonicalDocument` be the result of applying the
JSON Canonicalization Scheme [[RFC8785]] to a JSON serialization of the
`unsecuredDocument`.
</li>
<li>
Return `canonicalDocument` as the <em>transformed data document</em>.