class ClientTlsSession {

  public byte[] startHandshake() {
    if (clientHello != null) {
      throw new IllegalStateException("Already started");
    }

    final ClientHello ch = ClientHello.defaults(kek, transportParameters);
    clientHello = Bytes.write(bb -> ch.write(bb, true));
    return clientHello;
  }

  public  ClientTlsSession(
      final AEAD initialAEAD,
      final TransportParameters transportParameters,
      final CertificateValidator certificateValidator);

}