# File lib/u2f/fake_u2f.rb, line 46
  def sign_response(challenge)
    client_data_json = client_data(U2F::ClientData::AUTHENTICATION_TYP, challenge)
    JSON.dump(
      :clientData => U2F.urlsafe_encode64(client_data_json),
      :keyHandle => U2F.urlsafe_encode64(key_handle_raw),
      :signatureData => auth_signature_data(client_data_json)
    )
  end