Message Authentication Code for the Network Time Protocol
draft-ietf-ntp-mac-03

Document Type Active Internet-Draft (ntp WG)
Last updated 2017-10-30
Replaces draft-aanchal4-ntp-mac
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Internet Engineering Task Force                              A. Malhotra
Internet-Draft                                               S. Goldberg
Intended status: Standards Track                       Boston University
Expires: May 3, 2018                                    October 30, 2017

       Message Authentication Code for the Network Time Protocol
                         draft-ietf-ntp-mac-03

Abstract

   RFC 5905 [RFC5905] states that Network Time Protocol (NTP) packets
   should be authenticated by appending a 128-bit key to the NTP data,
   and hashing the result with MD5 to obtain a 128-bit tag.  This
   document deprecates MD5-based authentication, which is considered to
   be too weak, and recommends the use of AES-CMAC [RFC4493] as a
   replacement.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 3, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  Deprecating MD5 . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Replacement Recommendation  . . . . . . . . . . . . . . . . .   2
   4.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Test Vectors  . . . . . . . . . . . . . . . . . . . . . . . .   3
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   3
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   3
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   4

1.  Introduction

   RFC 5905 [RFC5905] states that Network Time Protocol (NTP) packets
   should be authenticated by appending a 128-bit key to the NTP data,
   and hashing the result with MD5 to obtain a 128-bit tag.  This
   document deprecates MD5-based authentication, which is considered to
   be too weak, and recommends the use of AES-CMAC [RFC4493] as a
   replacement.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  Deprecating MD5

   RFC 5905 [RFC5905] defines how the MD5 digest algorithm in RFC 1321
   [RFC1321] can be used as a message authentication code (MAC) for
   authenticating NTP packets.  However, as discussed in [BCK] and RFC
   6151 [RFC6151], this is not a secure MAC and therefore MUST be
   deprecated.

3.  Replacement Recommendation

   If authentication is implemented, then AES-CMAC as specified in RFC
   4493 [RFC4493] SHOULD be computed over all fields in the NTP header,
   and any extension fields that are present in the NTP packet as
   described in RFC 5905 [RFC5905].  The MAC key for NTP SHOULD be 128
   bits long AES-128 key and the resulting MAC tag SHOULD be 128 bits

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