const backFromHexPublicKey = isoUint8Array.fromHex(previousAuthenticator.credentialID);

// Saving :
const hexCredentialID = isoUint8Array.toHex(verification.registrationInfo.credentialID);
const hexCredentialPublicKey = isoUint8Array.toHex(verification.registrationInfo.credentialPublicKey);

// Authentification Option : 
const previousAuthenticator = await Authenticator.findOne({ userId: user._id });
const credentialIDbackFromHex = isoUint8Array.fromHex(previousAuthenticator.credentialID);
console.log('credentialIDbackFromHex = ', credentialIDbackFromHex ); // The "restored" uInt8Array is the same !

const options = await generateAuthenticationOptions({
  rpID,
  allowCredentials: [
    {
      id: credentialIDbackFromHex ,
      type: 'public-key',
      transports: previousAuthenticator.transports,
    },
  ],
  userVerification: 'preferred',
});

const previousAuthenticator = await Authenticator.findOne({ userId: user?._id });
try {
  const backFromHexCredentialID = isoUint8Array.fromHex(previousAuthenticator.credentialID);
  const backFromHexPublicKey = isoUint8Array.fromHex(previousAuthenticator.credentialID);

  verification = await verifyAuthenticationResponse({
    response: challengeResponse,
    expectedChallenge: user?.challenge,
    expectedOrigin: origin,
    expectedRPID: rpID,
    authenticator: {
      ...previousAuthenticator,
      credentialID: backFromHexCredentialID,
      credentialPublicKey: backFromHexPublicKey,
    },
    requireUserVerification: true,
  });
  res.status(200).json({ ok: verification.verified });
} catch (error) {
  console.error(error);
  return res.status(400).send({ message: error.message });
}