EcdsaSecp256k1RecoverySignature2020

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Suite Details

Per ld-signatures, this Signature Suite defines the following:

{
  "id": "https://identity.foundation/EcdsaSecp256k1RecoverySignature2020#EcdsaSecp256k1RecoverySignature2020",
  "type": "SignatureSuite",
  "canonicalizationAlgorithm": "https://w3id.org/security#URDNA2015",
  "digestAlgorithm": "https://www.ietf.org/assignments/jwa-parameters#SHA256",
  "signatureAlgorithm": "https://tools.ietf.org/html/rfc4880#section-11.4"
}

Examples

Terminology

publicKeyJwk

A jwk secp256k1 public key.

{
  "id": "did:example:123#vm-1",
  "controller": "did:example:123",
  "type": "EcdsaSecp256k1RecoveryMethod2020",
  "publicKeyJwk": {
    "crv": "secp256k1",
    "kid": "JUvpllMEYUZ2joO59UNui_XYDqxVqiFLLAJ8klWuPBw",
    "kty": "EC",
    "x": "dWCvM4fTdeM0KmloF57zxtBPXTOythHPMm1HCLrdd3A",
    "y": "36uMVGM7hnw-N6GnjFcihWE3SkrhMLzzLCdPMXPEXlA"
  }
}

privateKeyJwk

A jwk secp256k1 private key.

{
  "id": "did:example:123#vm-1",
  "controller": "did:example:123",
  "type": "EcdsaSecp256k1RecoveryMethod2020",
  "privateKeyJwk": {
    "crv": "secp256k1",
    "d": "rhYFsBPF9q3-uZThy7B3c4LDF_8wnozFUAEm5LLC4Zw",
    "kid": "JUvpllMEYUZ2joO59UNui_XYDqxVqiFLLAJ8klWuPBw",
    "kty": "EC",
    "x": "dWCvM4fTdeM0KmloF57zxtBPXTOythHPMm1HCLrdd3A",
    "y": "36uMVGM7hnw-N6GnjFcihWE3SkrhMLzzLCdPMXPEXlA"
  }
}

publicKeyHex

A hex encoded secp256k1 compressed public key.

{
  "id": "did:example:123#key-0",
  "type": "EcdsaSecp256k1RecoverySignature2020",
  "publicKeyHex": "027560af3387d375e3342a6968179ef3c6d04f5d33b2b611cf326d4708badd7770"
}

privateKeyHex

A hex encoded secp256k1 compressed private key.

{
  "id": "did:example:123#key-0",
  "type": "EcdsaSecp256k1RecoverySignature2020",
  "publicKeyHex": "278a5de700e29faae8e40e366ec5012b5ec63d36ec77e8a2417154cc1d25383f"
}

ethereumAddress

A hex encoded ethereumAddress address.

{
  "id": "did:example:123#key-0",
  "type": "EcdsaSecp256k1RecoverySignature2020",
  "ethereumAddress": "0x89a932207c485f85226d86f7cd486a89a24fcc12"
}

ES256K-R

This suite uses detached JWS using alg “ES256K-R” an unregistered, experimental ECDSA over secp256k1 with encoded recovery bit. Please review the details below.

ES256K-R is just ES256K with the recovery bit appended… making the signature 65 bytes instead of 64.

The recovery bit is used to extract the public key from the signature. See here.

^ please recommend a better source for describing ecdsa secp256k1 recoverable signature format.

The detached JWS must have the following header:

{
  "alg": "ES256K-R",
  "b64": false,
  "crit": ["b64"]
}

This is what a proof with EcdsaSecp256k1RecoverySignature2020 looks like:

{
  "type": "EcdsaSecp256k1RecoverySignature2020",
  "created": "2020-04-11T21:07:06Z",
  "verificationMethod": "did:example:123#vm-3",
  "proofPurpose": "assertionMethod",
  "jws": "eyJhbGciOiJFUzI1NkstUiIsImI2NCI6ZmFsc2UsImNyaXQiOlsiYjY0Il19..pp9eiLCMfN4EfSB3cbl3UxJ4TtgUaTfByDaaB6IZbXsnvIy5AUIFjbgaiFNtq9-3f8mP7foD_HXpjrdWZfzlwAE"
}