This specification describes a JSON Web Signature Suite created in 2020 for the Linked Data Proof specification. The Signature Suite utilizes Detached JWS signatures to provide support for a subset of the digital signature algorithms registered with IANA.

This is an experimental specification and is undergoing regular revisions. It is not fit for production deployment.

Introduction

This specification defines a cryptographic suite for the purpose of creating, verifying proofs for JSON Web Signatures in conformance with the Linked Data Proofs [[LD-PROOFS]] specification.

In general the suites uses the RDF Dataset Normalization Algorithm [[RDF-DATASET-NORMALIZATION]] to transform an input document into its canonical form. The cannonical representation is then hashed and signed with a detached signature algorithm.

Terminology

The following terms are used to describe concepts involved in the generation and verification of the Linked Data Proof signature suite.

signature suite
A specified set of cryptographic primitives typically consisting of a canonicalization algorithm, a message digest algorithm, and a signature algorithm that are bundled together by cryptographers for developers for the purposes of safety and convenience.
canonicalization algorithm
An algorithm that takes an input document that has more than one possible representation and always transforms it into a canonical form. This process is sometimes also called normalization.
message digest algorithm
An algorithm that takes a message, prefferably in some canonical form and produces a cryptographic output called a digest that is often many orders of magnitude smaller than the input message. These algorithms are often 1) very fast, 2) non-reversible, 3) cause the output to change significantly when even one bit of the input message changes, and 4) make it infeasible to find two different inputs for the same output.
canonical form
The output of applying a canonicalization algorithm to an input document.
signature algorithm
An algorithm that takes an input message and produces an output value where the receiver of the message can mathematically verify that the message has not been modified in transit and came from someone possessing a particular secret.
linked data document
A document comprised of linked data.
linked data proof
A linked data proof which is a set of attributes that represent a linked data digital proof and the parameters required to verify it as defined by [[RDF-N-Quads]].
linked data proof document
A linked data document featuring one or more linked data proofs.
JsonWebKey2020
The type of the verification method for the signature suite JsonWebSignature2020.
JsonWebSignature2020
The type of the linked data proof for the signature suite JsonWebSignature2020.

Suite Definition

The JSON Web Signature signature suite 2020 MUST be used in conjunction with the signing and verification algorithms in the Linked Data Proofs [[LD-PROOFS]] specification. The suite consists of the following algorithms:

Parameter Value Specification
canonicalization algorithm https://w3id.org/security#URDNA2015 [[RDF-DATASET-NORMALIZATION]]
message digest algorithm SHA-256 [[RFC4634]]
signature algorithm JSON Web Signature (JWS) Unencoded Payload Option [[RFC7797]]

JOSE Conformance

This suite support cryptographic agility, see [[RFC7696]]. This table maps a key type to a subset of [[IANA_JOSE]] supported signing and encryption algorithms.

kty crvOrSize signature keyAgreement encryption
OKP Ed25519 EdDSA ECDH-ES+A256KW
OKP X25519 ECDH ECDH-ES+A256KW
EC secp256k1 ES256K ECDH ECDH-ES+A256KW
EC P-256 ES256 ECDH ECDH-ES+A256KW
EC P-384 ES384 ECDH ECDH-ES+A256KW
RSA 2048+ PS256 RSA-OAEP

Verification Method

The cryptographic material used to verify a linked data proof is called the verification method.

This suite relies on public key material represented using [[RFC7517]].

This suite supports public key use for both digital signature verification, according to [[RFC7515]], and key agreement according to [[RFC8037]].

This suite MAY be used to verify linked data proofs produced by key material in any representation that can be converted to JWK, however it is RECOMMENDED that this suite be used with verification method's of type JsonWebKey2020.

JSON Web Key 2020

The id of the verification method SHOULD be the JWK thumbprint calculated from the publicKeyJwk property value according to [[RFC7638]].

The type of the verification method SHOULD be JsonWebKey2020.

The controller of the verification method SHOULD be a URI.

The publicKeyJwk property of the verification method SHOULD be a JWK formatted according to [[RFC7517]].

Be careful not to accidentally publish the JWK representation of a private key. See rfc7517#appendix-A.2 for examples of private key representations. The property publicKeyJwk MUST never contain "d". 

            {
              "id": "https://example.com/issuer/123#ovsDKYBjFemIy8DVhc-w2LSi8CvXMw2AYDzHj04yxkc",
              "type": "JsonWebKey2020",
              "controller": "https://example.com/issuer/123",
              "publicKeyJwk": {
                "kty": "OKP",
                "crv": "Ed25519",
                "x": "CV-aGlld3nVdgnhoZK0D36Wk-9aIMlZjZOK2XhPMnkQ"
              }
            }
          
            {
              "@context": ["https://www.w3.org/ns/did/v1", "https://w3id.org/security/suites/jws-2020/v1"],
              "id": "did:example:123",
              "publicKey": [
                {
                  "id": "did:example:123#_Qq0UL2Fq651Q0Fjd6TvnYE-faHiOpRlPVQcY_-tA4A",
                  "type": "JsonWebKey2020",
                  "controller": "did:example:123",
                  "publicKeyJwk": {
                    "kty": "OKP",
                    "crv": "Ed25519",
                    "x": "VCpo2LMLhn6iWku8MKvSLg2ZAoC-nlOyPVQaO3FxVeQ"
                  }
                },
                {
                  "id": "did:example:123#4SZ-StXrp5Yd4_4rxHVTCYTHyt4zyPfN1fIuYsm6k3A",
                  "type": "JsonWebKey2020",
                  "controller": "did:example:123",
                  "publicKeyJwk": {
                    "kty": "EC",
                    "crv": "secp256k1",
                    "x": "Z4Y3NNOxv0J6tCgqOBFnHnaZhJF6LdulT7z8A-2D5_8",
                    "y": "i5a2NtJoUKXkLm6q8nOEu9WOkso1Ag6FTUT6k_LMnGk"
                  }
                },
                {
                  "id": "did:example:123#n4cQ-I_WkHMcwXBJa7IHkYu8CMfdNcZKnKsOrnHLpFs",
                  "type": "JsonWebKey2020",
                  "controller": "did:example:123",
                  "publicKeyJwk": {
                    "kty": "RSA",
                    "e": "AQAB",
                    "n": "omwsC1AqEk6whvxyOltCFWheSQvv1MExu5RLCMT4jVk9khJKv8JeMXWe3bWHatjPskdf2dlaGkW5QjtOnUKL742mvr4tCldKS3ULIaT1hJInMHHxj2gcubO6eEegACQ4QSu9LO0H-LM_L3DsRABB7Qja8HecpyuspW1Tu_DbqxcSnwendamwL52V17eKhlO4uXwv2HFlxufFHM0KmCJujIKyAxjD_m3q__IiHUVHD1tDIEvLPhG9Azsn3j95d-saIgZzPLhQFiKluGvsjrSkYU5pXVWIsV-B2jtLeeLC14XcYxWDUJ0qVopxkBvdlERcNtgF4dvW4X00EHj4vCljFw"
                  }
                },
                {
                  "id": "did:example:123#_TKzHv2jFIyvdTGF1Dsgwngfdg3SH6TpDv0Ta1aOEkw",
                  "type": "JsonWebKey2020",
                  "controller": "did:example:123",
                  "publicKeyJwk": {
                    "kty": "EC",
                    "crv": "P-256",
                    "x": "38M1FDts7Oea7urmseiugGW7tWc3mLpJh6rKe7xINZ8",
                    "y": "nDQW6XZ7b_u2Sy9slofYLlG03sOEoug3I0aAPQ0exs4"
                  }
                },
                {
                  "id": "did:example:123#8wgRfY3sWmzoeAL-78-oALNvNj67ZlQxd1ss_NX1hZY",
                  "type": "JsonWebKey2020",
                  "controller": "did:example:123",
                  "publicKeyJwk": {
                    "kty": "EC",
                    "crv": "P-384",
                    "x": "GnLl6mDti7a2VUIZP5w6pcRX8q5nvEIgB3Q_5RI2p9F_QVsaAlDN7IG68Jn0dS_F",
                    "y": "jq4QoAHKiIzezDp88s_cxSPXtuXYFliuCGndgU4Qp8l91xzD1spCmFIzQgVjqvcP"
                  }
                },
                {
                  "id": "did:example:123#NjQ6Y_ZMj6IUK_XkgCDwtKHlNTUTVjEYOWZtxhp1n-E",
                  "type": "JsonWebKey2020",
                  "controller": "did:example:123",
                  "publicKeyJwk": {
                    "kty": "EC",
                    "crv": "P-521",
                    "x": "AVlZG23LyXYwlbjbGPMxZbHmJpDSu-IvpuKigEN2pzgWtSo--Rwd-n78nrWnZzeDc187Ln3qHlw5LRGrX4qgLQ-y",
                    "y": "ANIbFeRdPHf1WYMCUjcPz-ZhecZFybOqLIJjVOlLETH7uPlyG0gEoMWnIZXhQVypPy_HtUiUzdnSEPAylYhHBTX2"

                  }
                }
              ],
              "authentication": [
                "did:example:123#_Qq0UL2Fq651Q0Fjd6TvnYE-faHiOpRlPVQcY_-tA4A",
                "did:example:123#4SZ-StXrp5Yd4_4rxHVTCYTHyt4zyPfN1fIuYsm6k3A",
                "did:example:123#n4cQ-I_WkHMcwXBJa7IHkYu8CMfdNcZKnKsOrnHLpFs",
                "did:example:123#_TKzHv2jFIyvdTGF1Dsgwngfdg3SH6TpDv0Ta1aOEkw",
                "did:example:123#8wgRfY3sWmzoeAL-78-oALNvNj67ZlQxd1ss_NX1hZY",
                "did:example:123#NjQ6Y_ZMj6IUK_XkgCDwtKHlNTUTVjEYOWZtxhp1n-E"
              ],
              "assertionMethod": [
                "did:example:123#_Qq0UL2Fq651Q0Fjd6TvnYE-faHiOpRlPVQcY_-tA4A",
                "did:example:123#4SZ-StXrp5Yd4_4rxHVTCYTHyt4zyPfN1fIuYsm6k3A",
                "did:example:123#n4cQ-I_WkHMcwXBJa7IHkYu8CMfdNcZKnKsOrnHLpFs",
                "did:example:123#_TKzHv2jFIyvdTGF1Dsgwngfdg3SH6TpDv0Ta1aOEkw",
                "did:example:123#8wgRfY3sWmzoeAL-78-oALNvNj67ZlQxd1ss_NX1hZY",
                "did:example:123#NjQ6Y_ZMj6IUK_XkgCDwtKHlNTUTVjEYOWZtxhp1n-E"
              ],
              "capabilityDelegation": [
                "did:example:123#_Qq0UL2Fq651Q0Fjd6TvnYE-faHiOpRlPVQcY_-tA4A",
                "did:example:123#4SZ-StXrp5Yd4_4rxHVTCYTHyt4zyPfN1fIuYsm6k3A",
                "did:example:123#n4cQ-I_WkHMcwXBJa7IHkYu8CMfdNcZKnKsOrnHLpFs",
                "did:example:123#_TKzHv2jFIyvdTGF1Dsgwngfdg3SH6TpDv0Ta1aOEkw",
                "did:example:123#8wgRfY3sWmzoeAL-78-oALNvNj67ZlQxd1ss_NX1hZY",
                "did:example:123#NjQ6Y_ZMj6IUK_XkgCDwtKHlNTUTVjEYOWZtxhp1n-E"
              ],
              "capabilityInvocation": [
                "did:example:123#_Qq0UL2Fq651Q0Fjd6TvnYE-faHiOpRlPVQcY_-tA4A",
                "did:example:123#4SZ-StXrp5Yd4_4rxHVTCYTHyt4zyPfN1fIuYsm6k3A",
                "did:example:123#n4cQ-I_WkHMcwXBJa7IHkYu8CMfdNcZKnKsOrnHLpFs",
                "did:example:123#_TKzHv2jFIyvdTGF1Dsgwngfdg3SH6TpDv0Ta1aOEkw",
                "did:example:123#8wgRfY3sWmzoeAL-78-oALNvNj67ZlQxd1ss_NX1hZY",
                "did:example:123#NjQ6Y_ZMj6IUK_XkgCDwtKHlNTUTVjEYOWZtxhp1n-E"
              ]
            }

Proof Representation

The cryptographic material used to represent a linked data proof is called the proof type.

This suite relies on detached digital signatures represented using [[RFC7797]].

JSON Web Signature 2020

The verificationMethod property of the proof SHOULD be a URI. Dereferencing the verificationMethod SHOULD result in an object of type JsonWebKey2020.

The type property of the proof MUST be JsonWebSignature2020.

The created property of the proof MUST be an [[ISO_8601]] formated date string.

The proofPurpose property of the proof MUST be a string, and SHOULD match the verification relationship expressed by the verification method controller.

The jws property of the proof MUST be a detached JWS produced according to [[RFC7797]].

The header of the detached JWS MUST look like this: {"b64":false,"crit":["b64"],"alg":"PS256"} where alg is a value registered in [[IANA_JOSE]] AND is present in the supported algorithms table of this suite.

Test Vectors

The following test vectors are provided to assist with implementers.

        {
          "seed_0": "9b937b81322d816cfab9d5a3baacc9b2a5febe4b149f126b3630f93a29527017"
        }
      
        {
          "keypair_0": {
            "id": "#ovsDKYBjFemIy8DVhc-w2LSi8CvXMw2AYDzHj04yxkc",
            "type": "JsonWebKey2020",
            "controller": "did:key:z6Mkf5rGMoatrSj1f4CyvuHBeXJELe9RPdzo2PKGNCKVtZxP",
            "publicKeyJwk": {
              "kty": "OKP",
              "crv": "Ed25519",
              "x": "CV-aGlld3nVdgnhoZK0D36Wk-9aIMlZjZOK2XhPMnkQ"
            },
            "privateKeyJwk": {
              "kty": "OKP",
              "crv": "Ed25519",
              "x": "CV-aGlld3nVdgnhoZK0D36Wk-9aIMlZjZOK2XhPMnkQ",
              "d": "m5N7gTItgWz6udWjuqzJsqX-vksUnxJrNjD5OilScBc"
            }
          },
          "keypair_1": {
            "id": "#zaS0k3zk2KpT4NqqpdUA1YD0JVTOtQf3pNoKDI-wes0",
            "type": "JsonWebKey2020",
            "controller": "did:key:zQ3shP2mWsZYWgvgM11nenXRTx9L1yiJKmkf9dfX7NaMKb1pX",
            "publicKeyJwk": {
              "kty": "EC",
              "crv": "secp256k1",
              "x": "GBMxavme-AfIVDKqI6WBJ4V5wZItsxJ9muhxPByllHQ",
              "y": "SChlfVBhTXG_sRGc9ZdFeCYzI3Kbph3ivE12OFVk4jo"
            },
            "privateKeyJwk": {
              "kty": "EC",
              "crv": "secp256k1",
              "x": "GBMxavme-AfIVDKqI6WBJ4V5wZItsxJ9muhxPByllHQ",
              "y": "SChlfVBhTXG_sRGc9ZdFeCYzI3Kbph3ivE12OFVk4jo",
              "d": "m5N7gTItgWz6udWjuqzJsqX-vksUnxJrNjD5OilScBc"
            }
          },
          "keypair_2": {
            "id": "#zwlFQYyCqQXZ3nzpxkxJFxlpGU2l8LZQ9gxIxDdEhuY",
            "type": "JsonWebKey2020",
            "controller": "did:key:zUewtYk1yGS3SWp7kxrFK3DZRHMFbGEnrgFrqsi6hG8Z7EpRzbMP7d5y49HhrUv4tgV4DHCSoQUtF1NRNe43bymdi7K91PkwEGJRR4jv4Vb2mu2ZcBJXbw3d35JfqsVeLcwXFUi",
            "publicKeyJwk": {
              "kty": "EC",
              "crv": "P-384",
              "x": "eQbMauiHc9HuiqXT894gW5XTCrOpeY8cjLXAckfRtdVBLzVHKaiXAAxBFeVrSB75",
              "y": "YOjxhMkdH9QnNmGCGuGXJrjAtk8CQ1kTmEEi9cg2R9ge-zh8SFT1Xu6awoUjK5Bv"
            },
            "privateKeyJwk": {
              "kty": "EC",
              "crv": "P-384",
              "x": "eQbMauiHc9HuiqXT894gW5XTCrOpeY8cjLXAckfRtdVBLzVHKaiXAAxBFeVrSB75",
              "y": "YOjxhMkdH9QnNmGCGuGXJrjAtk8CQ1kTmEEi9cg2R9ge-zh8SFT1Xu6awoUjK5Bv",
              "d": "dXghMAzYZmv46SNRuxmfDIuAlv7XIhvlkPzW3vXsopB1ihWp47tx0hqjZmYO6fJa"
            }
          }
        }
      
        {
          "message_0": "hello world"
        }
      
        {
          "signature_0": "eyJhbGciOiJFZERTQSIsImI2NCI6ZmFsc2UsImNyaXQiOlsiYjY0Il19..v_Tni1_9lPQsS52GOnCMTFp7vDRjZIcj3pmuY1mF9W7nMAH94DpGecNwdFsXrz09n9bDTd8gJFqXWZeWIGvUAA",
          "signature_1": "eyJhbGciOiJFUzI1NksiLCJiNjQiOmZhbHNlLCJjcml0IjpbImI2NCJdfQ..dsgrLHXb5-VsUKVop4JJyO9dkFvJKRVNeOcEDD9nBAl3MqzJrJYfEfL8wArG-9ZjL12UD8btrJljZ7_C8p51mA"
        }
      
        {
          "issuer_0": {
            "@context": [
              "https://www.w3.org/ns/did/v1",
              "https://w3id.org/security/suites/jws-2020/v1",
              {
                "@base": "https://example.com/issuer/123"
              }
            ],
            "id": "https://example.com/issuer/123",
            "publicKey": [
              {
                "id": "#ovsDKYBjFemIy8DVhc-w2LSi8CvXMw2AYDzHj04yxkc",
                "type": "JsonWebKey2020",
                "controller": "https://example.com/issuer/123",
                "publicKeyJwk": {
                  "kty": "OKP",
                  "crv": "Ed25519",
                  "x": "CV-aGlld3nVdgnhoZK0D36Wk-9aIMlZjZOK2XhPMnkQ"
                }
              }
            ],
            "assertionMethod": ["#ovsDKYBjFemIy8DVhc-w2LSi8CvXMw2AYDzHj04yxkc"]
          }
        }

      
        {
          "vc_template_0": {
            "@context": [
              "https://www.w3.org/2018/credentials/v1",
              "https://www.w3.org/2018/credentials/examples/v1",
              "https://w3id.org/security/suites/jws-2020/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"
              }
            }
          },
          "vc_0": {
            "@context": [
              "https://www.w3.org/2018/credentials/v1",
              "https://www.w3.org/2018/credentials/examples/v1",
              "https://w3id.org/security/suites/jws-2020/v1"
            ],
            "id": "http://example.gov/credentials/3732",
            "type": ["VerifiableCredential", "UniversityDegreeCredential"],
            "issuer": {
              "id": "https://example.com/issuer/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": "2019-12-11T03:50:55Z",
              "jws": "eyJhbGciOiJFZERTQSIsImI2NCI6ZmFsc2UsImNyaXQiOlsiYjY0Il19..MJ5GwWRMsadCyLNXU_flgJtsS32584MydBxBuygps_cM0sbU3abTEOMyUvmLNcKOwOBE1MfDoB1_YY425W3sAg",
              "proofPurpose": "assertionMethod",
              "verificationMethod": "https://example.com/issuer/123#ovsDKYBjFemIy8DVhc-w2LSi8CvXMw2AYDzHj04yxkc"
            }
          }
        }

A conforming document is any concrete expression of the data model that complies with the normative statements in this specification. Specifically, all relevant normative statements in Sections and of this document MUST be enforced.

A conforming processor is any algorithm realized as software and/or hardware that generates or consumes a conforming document. Conforming processors MUST produce errors when non-conforming documents are consumed.

This document also contains examples that contain JSON and JSON-LD content. Some of these examples contain characters that are invalid JSON, 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.

Security Considerations

The following section describes security considerations that developers implementing this specification should be aware of in order to create secure software.

This specification relies on URDNA2015, please review [[RDF-DATASET-NORMALIZATION]].

This specification relies on [[IANA_JOSE]], please review [[RFC8725]].

TODO: We need to add a complete list of security considerations.