Diffie-Helman USM Key Management Information Base and Textual Convention
RFC 2786

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Network Working Group                                        M. St. Johns
Request for Comments: 2786                                    Excite@Home
Category: Experimental                                         March 2000

                         Diffie-Helman USM Key
           Management Information Base and Textual Convention

Status of this Memo

   This memo defines an Experimental Protocol for the Internet
   community.  It does not specify an Internet standard of any kind.
   Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

IESG Note

   This document specifies an experimental MIB. Readers, implementers
   and users of this MIB should be aware that in the future the IETF may
   charter an IETF Working Group to develop a standards track MIB to
   address the same problem space that this MIB addresses.  It is quite
   possible that an incompatible standards track MIB may result from
   that effort.

Abstract

   This memo defines an experimental portion of the Management
   Information Base (MIB) for use with network management protocols in
   the Internet community.  In particular, it defines a textual
   convention for doing Diffie-Helman key agreement key exchanges and a
   set of objects which extend the usmUserTable to permit the use of a
   DH key exchange in addition to the key change method described in
   [12]. In otherwords, this MIB adds the possibility of forward secrecy
   to the USM model.  It also defines a set of objects that can be used
   to kick start security on an SNMPv3 agent when the out of band path
   is authenticated, but not necessarily private or confidential.

   The KeyChange textual convention described in [12] permits secure key
   changes, but has the property that if a third-party has knowledge of
   the original key (e.g. if the agent was manufactured with a standard
   default key) and could capture all SNMP exchanges, the third-party
   would know the new key.  The Diffie-Helman key change described here

St. Johns                     Experimental                      [Page 1]
RFC 2786                 Diffie-Helman USM Key                March 2000

   limits knowledge of the new key to the agent and the manager making
   the change.  In otherwords, this process adds forward secrecy to the
   key change process.

   The recommendation in [12] is that the usmUserTable be populated out
   of band - e.g. not via SNMP.  If the number of agents to be
   configured is small, this can be done via a console port and
   manually.  If the number of agents is large, as is the case for a
   cable modem system, the manual approach doesn't scale well.  The
   combination of the two mechanisms specified here - the DH key change
   mechanism, and the DH key ignition mechanism - allows managable use
   of SNMPv3 USM in a system of millions of devices.

   This memo specifies a MIB module in a manner that is compliant to the
   SNMP SMIv2[5][6][7].  The set of objects is consistent with the SNMP
   framework and existing SNMP standards and is intended for use with
   the SNMPv3 User Security Model MIB and other security related MIBs.

   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 [16].

   This memo is a private submission by the author, but is applicable to
   the SNMPv3 working group within the Internet Engineering Task Force.
   Comments are solicited and should be addressed to the the author.

Table of Contents

   1 The SNMP Management Framework .................................   2
   1.1 Structure of the MIB ........................................   3
   2 Theory of Operation ...........................................   4
   2.1 Diffie-Helman Key Changes ...................................   4
   2.2 Diffie-Helman Key Ignition ..................................   4
   3 Definitions ...................................................   6
   4 References ....................................................  17
   5 Security Considerations .......................................  18
   6 Intellectual Property .........................................  19
   7 Author's Address ..............................................  19
   8 Full Copyright Statement ......................................  20

1.  The SNMP Management Framework   The SNMP Management Framework
   presently consists of five major components:

   o   An overall architecture, described in RFC 2271 [1].

   o   Mechanisms for describing and naming objects and events for the
       purpose of management. The first version of this Structure of
       Management Information (SMI) is called SMIv1 and described in STD

St. Johns                     Experimental                      [Page 2]
RFC 2786                 Diffie-Helman USM Key                March 2000