Generate JWK key pair

genJWK.js

import crypto from 'crypto'
import { writeFileSync } from 'fs'

async function exportCryptoKeyToPEM(key) {
  const exported = await crypto.subtle.exportKey('pkcs8', key)

  const pemExported = `-----BEGIN PRIVATE KEY-----\n${Buffer.from(exported).toString('base64')}\n-----END PRIVATE KEY-----`

  return pemExported
}

async function exportCryptoKeyToJWK(key) {
  const exported = await crypto.subtle.exportKey('jwk', key)

  return exported
}

const keyGenParams = {
  name: 'ECDSA',
  namedCurve: 'P-256',
}

const kid = crypto.createHash('sha1').update(crypto.randomBytes(16)).digest('hex')

const keyPair = await crypto.subtle.generateKey(keyGenParams, true, ['sign', 'verify'])

const pem = await exportCryptoKeyToPEM(keyPair.privateKey)
const jwk = await exportCryptoKeyToJWK(keyPair.publicKey)

jwk.kid = kid
jwk.alg = 'ES256'
jwk.use = 'sig'
delete jwk.key_ops
delete jwk.ext

writeFileSync(`./${kid}.pem`, pem)
writeFileSync('./jwk.json', JSON.stringify(jwk))