A Secure Selection and Filtering Mechanism for the Network Time Protocol Version 4
draft-schiff-ntp-chronos-03

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Network Working Group                                        N. R.Schiff
Internet-Draft                                                  D. Dolev
Intended status: Informational            Hebrew University of Jerusalem
Expires: March 5, 2020                                        T. Mizrahi
                                        Huawei Network.IO Innovation Lab
                                                             M. Schapira
                                          Hebrew University of Jerusalem
                                                       September 2, 2019

A Secure Selection and Filtering Mechanism for the Network Time Protocol
                               Version 4
                      draft-schiff-ntp-chronos-03

Abstract

   The Network Time Protocol version 4 (NTPv4) defines the peer process,
   the clock filter algorithm, the system process and the clock
   description algorithm.  The clock filter algorithm and the system
   process, as defined in RFC 5905, are the mechanism according to which
   an NTP client chooses the NTP servers it synchronized with.  This
   document specifies an alternative set of client mechanisms, named
   Chronos, that is backward compatible with NTPv4, and offers an
   improved level of security against time shifting attacks.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on March 5, 2020.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

R.Schiff, et al.          Expires March 5, 2020                 [Page 1]
Internet-Draft         NTP Extention with Chronos         September 2019

   This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   3
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Terms and Abbreviations . . . . . . . . . . . . . . . . .   3
     2.3.  Notations . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Extension for NTP Selection Process . . . . . . . . . . . . .   4
     3.1.  Peer calibration Process  . . . . . . . . . . . . . . . .   4
     3.2.  Chronos Selection Process . . . . . . . . . . . . . . . .   4
   4.  Chronos Pseudocode  . . . . . . . . . . . . . . . . . . . . .   5
   5.  Precision Vs. Security  . . . . . . . . . . . . . . . . . . .   5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   According to RFC 5905 [RFC5905], the NTP servers used for updating
   the client's time are chosen by the clock filter algorithm and the
   system process.  However, this method may be vulnerable to time
   shifting attacks, in which the attacker's goal is to shift the local
   time of an NTP client.  Time shifting attacks on NTP are possible
   even if all NTP communications are encrypted and authenticated.  This
   document introduces an improved system process with a secure
   algorithm called Chronos.  Chronos is backwards compatible with
   NTPv4, as an NTP client that runs Chronos is interoperable with
   [RFC5905]-compatible NTPv4 servers.

   Chronos achieves accurate synchronization even in the presence of
   powerful attackers who are in direct control of a large number of NTP
   servers.  Chronos leverages ideas from distributed computing