Message Authentication Codes for the Network Time Protocol
draft-aanchal4-ntp-mac-03

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Last updated 2017-03-27 (latest revision 2016-10-26)
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Internet Engineering Task Force                              A. Malhotra
Internet-Draft                                               S. Goldberg
Intended status: Standards Track                       Boston University
Expires: April 28, 2017                                 October 25, 2016

       Message Authentication Codes for the Network Time Protocol
                       draft-aanchal4-ntp-mac-02

Abstract

   The Network Time Protocol (NTP) RFC 5905 [RFC5905] uses a message
   authentication code (MAC) to cryptographically authenticate its UDP
   packets.  Currently, NTP packets are authenticated by appending a
   128-bit key to the NTP data, and hashing the result with MD5 to
   obtain a 128-bit tag.  However, as discussed in [BCK] and [RFC6151],
   this is not a secure MAC.  As such, this draft considers different
   secure MAC algorithms for use with NTP, evaluates their performance,
   and recommends the use of CMAC-AES [RFC4493].  We also suggest
   deprecating the use of MD5 as defined in [RFC5905] for authenticating
   NTP packets.

Status of This Memo

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   This Internet-Draft will expire on April 28, 2017.

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Malhotra & Goldberg      Expires April 28, 2017                 [Page 1]
Internet-Draft                MACs for NTP                  October 2016

   carefully, as they describe your rights and restrictions with respect
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  MAC Algorithms  . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Performance Requirements  . . . . . . . . . . . . . . . .   3
     3.2.  Security Requirements . . . . . . . . . . . . . . . . . .   4
   4.  Performance Results . . . . . . . . . . . . . . . . . . . . .   4
   5.  Other Hardware Platforms  . . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
     6.1.  Why is GMAC not suitable for NTP? . . . . . . . . . . . .   7
   7.  Use HMAC or CMAC instead  . . . . . . . . . . . . . . . . . .   9
   8.  GMAC-SIV - Another Potential MAC Candidate  . . . . . . . . .   9
   9.  Recommendations . . . . . . . . . . . . . . . . . . . . . . .  10
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  10
     11.2.  Informative References . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   NTP uses a message authentication code (MAC) to authenticate its
   packets.  Currently, NTP packets are authenticated by appending a
   128-bit key to the NTP data, and hashing the result with MD5 to
   obtain a 128-bit tag.  However, as discussed in [BCK] and [RFC6151],
   this not a secure MAC.  As such, this draft considers different
   secure MAC algorithms for use with NTP, evaluates their performance,
   and recommends the use of CMAC-AES [RFC4493].  We also suggest
   deprecating the use of MD5, as defined in [RFC5905], for
   authenticating NTP packets.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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