antelope-webauthn/_utils/create-antelope-key.js

A WebAuthn.io crypto utility for generating signatures, creating public keys, and verifying them, designed for Antelope-based blockchains such as Vaulta, WAX, and other related platforms. This package provides convenient tools to handle key pair generatio

import binary_to_base58 from "base58-js/binary_to_base58.js";
import ripemd160 from "ripemd160-js/ripemd160.js";
import decodeCBOR from "./cbor-decode.js";
export default async function createAntelopeWebAuthnPublicKey({ attestationObject, clientDataJSON, }) {
    const { authData } = decodeCBOR(attestationObject);
    const clientData = JSON.parse(new Uint8Array(clientDataJSON).reduce((acc, i) => (acc += String.fromCharCode(i)), ""));
    const rpid = new URL(clientData.origin).hostname;
    const rpid_hash = authData.slice(0, 32);
    const ripid_chars = [];
    for (let i = 0; i < rpid.length; i++)
        ripid_chars.push(rpid[i].charCodeAt(0));
    const check_hash = new Uint8Array(await crypto.subtle.digest("SHA-256", Uint8Array.from(ripid_chars)));
    new Uint8Array(check_hash).forEach((i, x) => {
        if (i != rpid_hash[x])
            throw new Error("Invalid rpid hash");
    });
    const CredIDLenBuffer = new Uint16Array(authData.slice(53, 55));
    const credIDLen = (CredIDLenBuffer[0] << 8) | CredIDLenBuffer[1]; // readUInt16BE
    const COSEPublicKey = authData.slice(55 + credIDLen, authData.length);
    const public_key = decodeCBOR(new Uint8Array(COSEPublicKey).buffer);
    const x = public_key[-2];
    const prefix = public_key[-3].slice(-1) & 1 ? 3 : 2;
    const webauthn_public_key = [
        prefix,
        ...x,
        2,
        ripid_chars.length,
        ...ripid_chars,
    ];
    const checksum = await ripemd160(Uint8Array.from([...webauthn_public_key, 87, 65]) // 87, 65 -> WA ascii
    );
    const antelope_public_key = "PUB_WA_" +
        binary_to_base58(Uint8Array.from([...webauthn_public_key, ...checksum.slice(0, 4)]));
    return antelope_public_key;
}