account-proof

account-proof.js

// Authentication Proof Service
{
  "f_type": "Service",
  "f_vsn": "1.0.0",
  "type": "account-proof",
  "method": "DATA",
  "uid": "fcl-dev-wallet#account-proof",
  "data": {
    "f_type": "account-proof",
    "f_vsn": "1.0.0",
    "address": "0x179b6b1cb6755e31",
    "timestamp": 1635272113264,
    "appDomainTag": "APP-V0.0-user",  // default
    "signatures": [
      {
        "f_type": "CompositeSignature",
        "f_vsn": "1.0.0",
        "addr": "0x179b6b1cb6755e31", // with prefix
        "keyId": 0,
        "signature": "542b9..."
      }
    ]
  }
}

// signature production

signature: sign(
  accountPrivateKey,
  fcl.WalletUtils.encodeMessageForProvableAuthnSigning(
    address,
    timestamp,
    appDomainTag
  )
)

import {ec as EC} from "elliptic"
import {SHA3} from "sha3"
const ec = new EC("p256")

const hashMsgHex = (msgHex: string) => {
  const sha = new SHA3(256)
  sha.update(Buffer.from(msgHex, "hex"))
  return sha.digest()
}

export function sign(accountPrivateKey: string, msgHex: string) {
  const key = ec.keyFromPrivate(Buffer.from(accountPrivateKey, "hex"))
  const sig = key.sign(hashMsgHex(msgHex))
  const n = 32
  const r = sig.r.toArrayLike(Buffer, "be", n)
  const s = sig.s.toArrayLike(Buffer, "be", n)
  return Buffer.concat([r, s]).toString("hex")
}