PublicKeyCredential: parseCreationOptionsFromJSON() static method

options

An object with the same structure as the Web Authentication API publicKey create credentials options object, but with base64url-encoded strings used in place of buffer properties.

An object with the Web Authentication API publicKey create credentials options object structure.

EncodingError DOMException

Thrown if any part of the options object cannot be converted into the publicKey create credentials options object structure.

The Web Authentication process for creating a key pair and registering a user involves a relying party server sending the web app information needed to create a credential, including details about the user identity, the relying party, and a "challenge". The web app passes this information to an authenticator to create the credential, by calling navigator.credentials.create() with an argument that contains the server-supplied data in the publicKey create credentials options object structure.

The specification does not define how the information needed for creating a credential is sent. A convenient approach is for the server to encapsulate the information in a JSON type representation of the publicKey create credentials options object that mirrors its structure but encodes buffer properties such as the challenge and user.id as base64url strings. This object can be serialized to a JSON string, sent to the web app and deserialized, and then converted to the publicKey create credentials options object structure using parseCreationOptionsFromJSON().

When registering a new user, a relying party server will supply information about the expected credentials to the web app. The code below defines this information in the form described in the options parameter above (taken from the "getting an AuthenticatorAttestationResponse" in AuthenticatorResponse):

const createCredentialOptionsJSON = {
  challenge:
    "21, 31, 105, " /* 29 more random bytes generated by the server in this string */,
  rp: {
    name: "Example CORP",
    id: "login.example.com",
  },
  user: {
    id: "16",
    name: "canand@example.com",
    displayName: "Carina Anand",
  },
  pubKeyCredParams: [
    {
      type: "public-key",
      alg: -7,
    },
  ],
};

Because this object only uses JSON data types, it can be serialized to JSON using JSON.stringify() and sent to the web app.

JSON.stringify(createCredentialOptionsJSON);

The web app can deserialize the JSON string back to a createCredentialOptionsJSON object (not shown). The parseCreationOptionsFromJSON() method is used to convert that object to the form that can be used in navigator.credentials.create():

// Convert options to form used by create()
const createCredentialOptions =
  PublicKeyCredential.parseCreationOptionsFromJSON(
    createCredentialOptionsJSON, // JSON-type representation
  );

navigator.credentials
  .create({ createCredentialOptions })
  .then((newCredentialInfo) => {
    // Handle the new credential information here.
  })
  .catch((err) => {
    console.error(err);
  });

• Web Authentication API
• PublicKeyCredential.parseRequestOptionsFromJSON()
• PublicKeyCredential.toJSON()