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<!DOCTYPE html>
<html>
<head>
<title>Data Integrity ECDSA Cryptosuites v1.0</title>
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title: "SEC 2: Recommended Elliptic Curve Domain Parameters",
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</head>
<body>
<section id="abstract">
<p>
This specification describes Data Integrity cryptosuites for use when
generating a digital signature using the Elliptic Curve Digital Signature
Algorithm (ECDSA).
</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-di-ecdsa-test-suite/">
implementation report</a>.
</p>
<p class="atrisk issue"
title="Features with less than two independent implementations">
Any feature with less than two independent implementations in the
<a href="https://w3c.github.io/vc-di-ecdsa-test-suite/">
ECDSA Cryptosuite Implementation Report</a> is an "at risk" feature and might be
removed before the transition to W3C Proposed Recommendation.
</p>
</section>
<section>
<h2>Introduction</h2>
<p>
This specification defines a cryptographic suite for the purpose of creating,
and verifying proofs for ECDSA signatures in conformance with the
Data Integrity [[VC-DATA-INTEGRITY]] specification. ECDSA signatures are
specified in [[FIPS-186-5]] with elliptic curves P-256 and P-384 specified in
[[NIST-SP-800-186]]. [[FIPS-186-5]] includes the <em>deterministic</em> ECDSA
algorithm which is also specified in [[RFC6979]].
</p>
<div class="note">
<p>
The elliptic curves P-256 and P-384 of [[NIST-SP-800-186]] are respectively referred
to as <em>secp256r1</em> and <em>secp384r1</em> in [[SECG2]]. This notation is
sometimes also used by ECDSA software libraries.
</p>
<p>
Developers are cautioned to not confuse <em>secp256<b>r</b>1</em> terms with
<em>secp256<b>k</b>1</em> terms; the latter are from a third, <em>different</em>,
elliptic curve, that is not used by this specification. ECDSA software libraries
might not implement all of these curves, so developers need to take care when
choosing an ECDSA software library for their implementation.
</p>
</div>
<p>
This specification uses either the RDF Dataset Canonicalization Algorithm
[[RDF-CANON]] or the JSON Canonicalization Scheme [[RFC8785]] to transform the
input document into its canonical form. It uses one of two mechanisms to digest
and sign: SHA-256 [[RFC6234]] as the message digest algorithm and ECDSA with
Curve P-256 as the signature algorithm, or SHA-384 [[RFC6234]] as the message
digest algorithm and ECDSA with Curve P-384 as the 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
[=conforming proof=]. 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. Such parts need to be
removed if implementers want 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>
These verification methods are used to verify Data Integrity Proofs
[[VC-DATA-INTEGRITY]] produced using Elliptic Curve cryptographic key material
that is compliant with [[FIPS-186-5]]. The encoding formats for these key types
are provided in this section. Lossless cryptographic key transformation
processes that result in equivalent cryptographic key material MAY be used
during 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` property represents a Multibase-encoded Multikey
expression of a P-256 or P-384 public key.
</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 ECDSA 256-bit public key value or
an ECDSA 384-bit public key value follows, as defined in the
<a data-cite="controller-document#Multikey">Multikey section</a> of
[[[controller-document]]]. 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 in the event of a
Multicodec value other than `0x1200` or `0x1201` being used in a
`publicKeyMultibase` value.
</p>
<pre class="example nohighlight"
title="An P-256 public key encoded as a Multikey">
{
"id": "https://example.com/issuer/123#key-0",
"type": "Multikey",
"controller": "https://example.com/issuer/123",
"publicKeyMultibase": "zDnaerx9CtbPJ1q36T5Ln5wYt3MQYeGRG5ehnPAmxcf5mDZpv"
}
</pre>
<pre class="example nohighlight"
title="An P-384 public key encoded as a Multikey">
{
"id": "https://example.com/issuer/123#key-0",
"type": "Multikey",
"controller": "https://example.com/issuer/123",
"publicKeyMultibase": "z82LkvCwHNreneWpsgPEbV3gu1C6NFJEBg4srfJ5gdxEsMGRJ
Uz2sG9FE42shbn2xkZJh54"
}
</pre>
<pre class="example nohighlight" title="Two public keys (P-256 and P-384)
encoded as Multikeys in a controller document">
{
"@context": [
"https://www.w3.org/ns/did/v1",
"https://w3id.org/security/multikey/v1"
],
"id": "did:example:123",
"verificationMethod": [{
"id": "https://example.com/issuer/123#key-1",
"type": "Multikey",
"controller": "https://example.com/issuer/123",
"publicKeyMultibase": "zDnaerx9CtbPJ1q36T5Ln5wYt3MQYeGRG5ehnPAmxcf5mDZpv"
}, {
"id": "https://example.com/issuer/123#key-2",
"type": "Multikey",
"controller": "https://example.com/issuer/123",
"publicKeyMultibase": "z82LkvCwHNreneWpsgPEbV3gu1C6NFJEBg4srfJ5gdxEsMGRJ
Uz2sG9FE42shbn2xkZJh54"
}],
"authentication": [
"did:example:123#key-1"
],
"assertionMethod": [
"did:example:123#key-2"
],
"capabilityDelegation": [
"did:example:123#key-2"
],
"capabilityInvocation": [
"did:example:123#key-2"
]
}
</pre>
<p>
The `secretKeyMultibase` property represents a Multibase-encoded Multikey
expression of a P-256 or P-384 secret key (also sometimes referred to as a
private key).
</p>
<p>
The `secretKeyMultibase` 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 ECDSA 256-bit secret key value or
an ECDSA 384-bit secret key value follows, as defined in the
<a data-cite="controller-document#Multikey">Multikey section</a> of
[[[controller-document]]]. Any other encoding MUST NOT be allowed.
</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 as 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 MUST be `ecdsa-rdfc-2019`,
`ecdsa-jcs-2019`, or `ecdsa-sd-2023`.
</p>
<p>
The value of the `proofValue` property is produced according to
the `cryptosuite` type and is specified in either
Section [[[#create-proof-ecdsa-rdfc-2019]]], or
Section [[[#create-proof-ecdsa-jcs-2019]]], or
Section [[[#create-base-proof-ecdsa-sd-2023]]], or
Section [[[#add-derived-proof-ecdsa-sd-2023]]].
</p>
<pre class="example nohighlight"
title="An ECDSA P-256 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": "ecdsa-rdfc-2019",
"created": "2023-02-24T23:36:38Z",
"verificationMethod": "https://vc.example/issuers/5678#zDnaepBuvsQ8cpsWrVKw8
fbpGpvPeNSjVPTWoq6cRqaYzBKVP",
"proofPurpose": "assertionMethod",
"proofValue": "z2iAR3F2Sk3mWfYyrinKzSQpSbvfxnz9kkv7roxxumB5RZDP9JUw5QAXuchUd
huiwE18hyyZTjiEreKmhH3oj9Q8"
}
}
</pre>
</section>
</section>
</section>
<section>
<h2>Algorithms</h2>
<p>
The following section describes multiple Data Integrity cryptographic suites
that utilize the Elliptic Curve Digital Signature Algorithm (ECDSA)
[[FIPS-186-5]]. When generating ECDSA signatures, the signature value MUST be
expressed according to section 7 of [[RFC4754]] (sometimes referred to as the
IEEE P1363 format) and encoded according to the specific cryptosuite proof
generation algorithm. All ECDSA signatures SHOULD use the <em>deterministic</em>
variant of the algorithm defined in [[FIPS-186-5]].
</p>
<p>
Implementations SHOULD fetch and cache verification method information as
early as possible when adding or verifying proofs. Parameters passed to
functions in this section use information from the verification method
— such as the public key size — to determine function parameters
— such as the cryptographic hashing algorithm.
</p>
<p id="canon-and-hash">
When the RDF Dataset Canonicalization Algorithm (RDFC-1.0) [[RDF-CANON]] is used
with ECDSA algorithms, the cryptographic hashing function used by RDFC-1.0 is
chosen based on the size of the associated public key. For P-256 keys, the
default hashing function, SHA-2 with 256 bits of output, MUST be used. For P-384
keys, SHA-2 with 384-bits of output MUST be used, specified via the RDFC-1.0
<a data-cite="RDF-CANON#dfn-hash-algorithm">implementation-specific parameter</a>.
</p>
<p class="advisement">
When the RDF Dataset Canonicalization Algorithm [[RDF-CANON]] is used,
implementations of that algorithm will detect
<a data-cite="RDF-CANON#dataset-poisoning">dataset poisoning</a>
by default, and abort processing upon detection.
</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 href="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 `ecdsa-rdfc-2019` then:
<ol class="algorithm">
<li>
Set |cryptosuite|.|createProof| to the algorithm in Section
[[[#create-proof-ecdsa-rdfc-2019]]].
</li>
<li>
Set |cryptosuite|.|verifyProof| to the algorithm in Section
[[[#proof-verification-ecdsa-rdfc-2019]]].
</li>
</ol>
</li>
<li>
If |options|.|cryptosuite| is `ecdsa-jcs-2019` then:
<ol class="algorithm">
<li>
Set |cryptosuite|.|createProof| to the algorithm in Section
[[[#create-proof-ecdsa-jcs-2019]]].
</li>
<li>
Set |cryptosuite|.|verifyProof| to the algorithm in Section
[[[#proof-verification-ecdsa-jcs-2019]]].
</li>
</ol>
</li>
<li>
If |options|.|cryptosuite| is `ecdsa-sd-2023` then:
<ol class="algorithm">
<li>
Set |cryptosuite|.|createProof| to the algorithm in Section
[[[#create-base-proof-ecdsa-sd-2023]]].
</li>
<li>
Set |cryptosuite|.|verifyProof| to the algorithm in Section
[[[#verify-derived-proof-ecdsa-sd-2023]]].
</li>
</ol>
</li>
<li>
Return |cryptosuite|.
</li>
</ol>
</section>
<section>
<h3>ecdsa-rdfc-2019</h3>
<p>
The `ecdsa-rdfc-2019` cryptographic suite takes an input document, canonicalizes
the document using the [[[RDF-CANON]]]
[[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>
<section>
<h4>Create Proof (ecdsa-rdfc-2019)</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-ecdsa-rdfc-2019]]] with
|options| passed as a parameter.
</li>
<li>
Let |transformedData| be the result of running the algorithm in Section <a
href="#transformation-ecdsa-rdfc-2019"></a> with |unsecuredDocument|,
|proofConfig|, and |options| passed as parameters.
</li>
<li>
Let |hashData| be the result of running the algorithm in Section
[[[#hashing-ecdsa-rdfc-2019]]] with |transformedData| and |proofConfig|
passed as a parameters.
</li>
<li>
Let |proofBytes| be the result of running the algorithm in Section
[[[#proof-serialization-ecdsa-rdfc-2019]]] 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 (ecdsa-rdfc-2019)</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>
<a data-cite="INFRA#nulls">Null</a>, if [=verification result/verified=] is
`false`; 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 |proofConfig| be 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-ecdsa-rdfc-2019"></a> with |unsecuredDocument| and
|proofConfig| passed as parameters.
</li>
<li>
Let |hashData| be the result of running the algorithm in Section
[[[#hashing-ecdsa-rdfc-2019]]] with |transformedData| and |proofConfig|
passed as a parameters.
</li>
<li>
Let |verified:boolean| be the result of running the algorithm in Section
[[[#proof-verification-ecdsa-rdfc-2019]]] 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>
|unsecuredDocument| if |verified| is `true`, otherwise <a data-cite="INFRA#nulls">Null</a></dd>
</dl>
</li>
</ol>
</section>
<section>
<h4>Transformation (ecdsa-rdfc-2019)</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-ecdsa-rdfc-2019]]].
</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 `ecdsa-rdfc-2019`,
an error MUST be raised and 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| to
<a data-cite="JSON-LD11-API#expansion-algorithm">JSON-LD expanded form</a>
and then <a data-cite="JSON-LD11-API#deserialize-json-ld-to-rdf-algorithm">
to RDF statements</a>, applying the <a data-cite="RDF-CANON#canon-algorithm">RDF Dataset Canonicalization
Algorithm</a> [[RDF-CANON]] to the result, and then serializing the result to a
<a data-cite="RDF-CANON#dfn-serialized-canonical-form">serialized canonical form</a> [[RDF-CANON]].
For canonicalization, one is expected to use a hash algorithm that has an appropriate security level for
the curve used; see <a href="#canon-and-hash">further details</a>.
</li>
<li>
Return |canonicalDocument| as the <em>transformed data document</em>.
</li>
</ol>
</section>
<section>
<h4>Hashing (ecdsa-rdfc-2019)</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-ecdsa-rdfc-2019]]] or
Section [[[#proof-verification-ecdsa-rdfc-2019]]]. One must use the hash
algorithm appropriate in security level to the curve used, i.e., for curve
P-256 one uses SHA-256 and for curve P-384 one uses SHA-384.
</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 |transformedDocumentHash| be the result of applying the
SHA-256 (SHA-2 with 256-bit output) or SHA-384 (SHA-2 with 384-bit output)
cryptographic hashing algorithm [[RFC6234]] to the
respective curve P-256 or curve P-384 |transformedDocument|.
Respective |transformedDocumentHash| will be exactly 32 or 48 bytes
in size.
</li>
<li>
Let |proofConfigHash| be the result of applying the
SHA-256 (SHA-2 with 256-bit output) or SHA-384 (SHA-2 with 384-bit output)
cryptographic hashing algorithm [[RFC6234]] to the respective curve P-256 or curve P-384
|canonicalProofConfig|. Respective |proofConfigHash|
will be exactly 32 or 48 bytes in size.
</li>
<li>
Let |hashData| be the result of joining |proofConfigHash| (the
first hash) with |transformedDocumentHash| (the second hash).
</li>
<li>
Return |hashData| as the <em>hash data</em>.
</li>
</ol>
</section>
<section>
<h4>Proof Configuration (ecdsa-rdfc-2019)</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-ecdsa-rdfc-2019">proof hashing algorithm</a>.
</p>
<p>
The required inputs to this algorithm are <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 `ecdsa-rdfc-2019`, 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 set and if the value 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|.<var>@context</var> to
|unsecuredDocument|.<var>@context</var>.
</li>
<li>
Let |canonicalProofConfig| be the result of applying the
[[[RDF-CANON]]] [[RDF-CANON]] to the |proofConfig|.
</li>
<li>
Return |canonicalProofConfig|.
</li>
</ol>
</section>
<section>
<h4>Proof Serialization (ecdsa-rdfc-2019)</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 (or a signing interface enabling the use of the private key
bytes) associated with the verification method identified by the
|options|.|verificationMethod| value.
</li>
<li>
Let |proofBytes| be the result of applying the Elliptic Curve Digital
Signature Algorithm (ECDSA) [[FIPS-186-5]], with |hashData| as the data
to be signed using the private key specified by |privateKeyBytes|.
|proofBytes| will be exactly 64 bytes in size for a P-256 key, and
96 bytes in size for a P-384 key.
</li>
<li>
Return |proofBytes| as the <em>digital proof</em>.
</li>
</ol>
</section>
<section>
<h4>Proof Verification (ecdsa-rdfc-2019)</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: Retrieve Verification Method</a>.
</li>
<li>
Let |verificationResult| be the result of applying the verification
algorithm Elliptic Curve Digital Signature Algorithm (ECDSA) [[FIPS-186-5]],
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>ecdsa-jcs-2019</h3>
<p>
The `ecdsa-jcs-2019` 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. The algorithms in this
section also include the verification of such a data integrity proof.
</p>
<section>
<h4>Create Proof (ecdsa-jcs-2019)</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 <var>unsecuredDocument</var>.<var>@context</var> is present, set
<var>proof</var>.<var>@context</var> to
<var>unsecuredDocument</var>.<var>@context</var>.
</li>
<li>
Let |proofConfig| be the result of running the algorithm in
Section [[[#proof-configuration-ecdsa-jcs-2019]]] with
|proof| passed as the <em>proof options</em> parameter.
</li>
<li>
Let |transformedData| be the result of running the algorithm in Section <a
href="#transformation-ecdsa-jcs-2019"></a> with |unsecuredDocument|
and |options| passed as parameters.
</li>
<li>
Let |hashData| be the result of running the algorithm in Section
[[[#hashing-ecdsa-jcs-2019]]] with |transformedData| and |proofConfig|
passed as a parameters.
</li>
<li>
Let |proofBytes| be the result of running the algorithm in Section
[[[#proof-serialization-ecdsa-jcs-2019]]] 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 (ecdsa-jcs-2019)</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>