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Versions: 00 01 02 03 04 05 06 07 08 09 RFC 3923

XMPP Working Group                                        P. Saint-Andre
Internet-Draft                                Jabber Software Foundation
Expires: June 29, 2004                                 December 30, 2003


 End-to-End Object Encryption in the Extensible Messaging and Presence
                            Protocol (XMPP)
                         draft-ietf-xmpp-e2e-07

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
   groups may also distribute working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at http://
   www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on June 29, 2004.

Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.

Abstract

   This memo defines a method for end-to-end object signing and
   encryption in the Extensible Messaging and Presence Protocol (XMPP).













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Table of Contents

   1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . .   3
   2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3. Securing Messages  . . . . . . . . . . . . . . . . . . . . . .   5
   4. Securing Presence  . . . . . . . . . . . . . . . . . . . . . .   6
   5. Securing Arbitrary XMPP Data . . . . . . . . . . . . . . . . .   8
   6. Rules for S/MIME Generation and Handling . . . . . . . . . . .   9
   7. Secure Communications Through a Gateway  . . . . . . . . . . .  12
   8. Security Considerations  . . . . . . . . . . . . . . . . . . .  13
   9. IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  13
      Normative References . . . . . . . . . . . . . . . . . . . . .  14
      Informative References . . . . . . . . . . . . . . . . . . . .  16
      Author's Address . . . . . . . . . . . . . . . . . . . . . . .  16
   A. Schema for urn:ietf:params:xml:ns:xmpp-e2e . . . . . . . . . .  16
   B. Revision History . . . . . . . . . . . . . . . . . . . . . . .  17
      Intellectual Property and Copyright Statements . . . . . . . .  19


































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1. Introduction

   This memo define a method for end-to-end signing and encryption in
   the Extensible Messaging and Presence Protocol (XMPP).  (For
   information about XMPP, see [XMPP-CORE] and [XMPP-IM].) The method
   defined herein enables a sender to encrypt and/or sign an instant
   message sent to a specific recipient, encrypt and/or sign presence
   information that is directed to a specific user, and sign presence
   information that is broadcasted to a specific user.  This memo
   thereby helps the XMPP specifications meet the requirements defined
   in [IMP-REQS].

1.1 Terminology

   This document inherits terminology defined in [SMIME], [IMP-MODEL],
   [CMS], and [XMPP-CORE].

   The capitalized 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
   [TERMS].

1.2 Discussion Venue

   The authors welcome discussion and comments related to the topics
   presented in this document.  The preferred forum is the
   <xmppwg@jabber.org> mailing list, for which archives and subscription
   information are available at <http://www.jabber.org/cgi-bin/mailman/
   listinfo/xmppwg/>.

1.3 Intellectual Property Notice

   This document is in full compliance with all provisions of Section 10
   of RFC 2026.  Parts of this specification use the term "jabber" for
   identifying namespaces and other protocol syntax.  Jabber[tm] is a
   registered trademark of Jabber, Inc.  Jabber, Inc. grants permission
   to the IETF for use of the Jabber trademark in association with this
   specification and its successors, if any.

2. Requirements

   For the purposes of this memo, we stipulate the following
   requirements:

   1.  The method defined MUST address encryption and signing
       requirements for minimal instant messaging and presence only, as
       those are defined in [IMP-REQS].  The method is NOT REQUIRED to
       support non-IM applications of XMPP, nor to support advanced



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       instant messaging and presence functionality that is outside the
       scope of [IMP-REQS].  In particular, the method MUST address the
       following requirements defined in [IMP-REQS]:

       *  The protocol MUST provide means to ensure confidence that a
          received message (NOTIFICATION or INSTANT MESSAGE) has not
          been corrupted or tampered with.  (Section 2.5.1)

       *  The protocol MUST provide means to ensure confidence that a
          received message (NOTIFICATION or INSTANT MESSAGE) has not
          been recorded and played back by an adversary.  (Section
          2.5.2)

       *  The protocol MUST provide means to ensure that a sent message
          (NOTIFICATION or INSTANT MESSAGE) is only readable by ENTITIES
          that the sender allows.  (Section 2.5.3)

       *  The protocol MUST allow any client to use the means to ensure
          non-corruption, non-playback, and privacy, but the protocol
          MUST NOT require that all clients use these means at all
          times.  (Section 2.5.4)

       *  When A establishes a SUBSCRIPTION to B's PRESENCE INFORMATION,
          the protocol MUST provide A means of verifying the accurate
          receipt of the content B chooses to disclose to A.  (Section
          5.1.4)

       *  The protocol MUST provide A means of verifying that the
          presence information is accurate, as sent by B.  (Section
          5.3.1)

       *  The protocol MUST provide A means of ensuring that no other
          PRINCIPAL C can see the content of M.  (Section 5.4.6)

       *  The protocol MUST provide A means of ensuring that no other
          PRINCIPAL C can tamper with M, and B means to verify that no
          tampering has occurred.  (Section 5.4.7)

   2.  The method defined MUST enable interoperability with non-XMPP
       messaging systems that support the Common Presence and Instant
       Messaging (CPIM) specifications defined by the Instant Messaging
       and Presence (IMPP) Working Group.  Therefore:

       *  Prior to encrypting or signing, the format of an instant
          message MUST conform to the CPIM Message Format defined in
          [MSGFMT].

       *  Prior to encrypting or signing, the format of presence



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          information MUST conform to the CPP Presence Information Data
          Format defined in [PIDF].

   3.  The method MUST follow the required procedures (including the
       specific algorithms) defined in [CPIM] and [CPP].  In particular,
       these documents specify:

       *  Encryption MUST use [SMIME] encryption with [CMS]
          EnvelopeData.

       *  Signing MUST use [SMIME] signatures with [CMS] SignedData.

   4.  In order to enable interoperable implementations, sending and
       receiving applications MUST implement the algorithms defined
       under Section 6.9.


3. Securing Messages

   In order to encrypt a message, a sending entity MUST use the
   following procedure:

   1.  Generate a "Message/CPIM" object as defined in [MSGFMT].

   2.  Encrypt and/or sign both the headers and content of the "Message/
       CPIM" object as specified in Requirement 3 of Section 2 above.

   3.  Provide the resulting multipart [SMIME] object (see [MULTI])
       within a CDATA section of an <e2e/> child of a <message/> stanza,
       where the <e2e/> element is qualified by the
       'urn:ietf:params:xml:ns:xmpp-e2e' namespace.

   Example 1: Sender generates "Message/CPIM" object:

   Content-type: Message/CPIM

   From: Juliet Capulet <im:juliet@example.com>
   To: Romeo Montague <im:romeo@example.net>
   DateTime: 2003-12-09T11:45:36.66Z
   Subject: Imploring

   Content-type: text/plain; charset=utf-8
   Content-ID: <1234567890@example.com>

   Wherefore art thou, Romeo?

   Example 2: Sender generates signed message (the 'from' address on the
   XMPP message stanza is stamped by sender's server):



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   <message to='romeo@example.net/orchard' type='chat'>
     <e2e xmlns='urn:ietf:params:xml:ns:xmpp-e2e'>
   <![CDATA[
   Content-Type: multipart/signed; boundary=next;
                 micalg=sha1;
                 protocol=application/pkcs7-signature

   --next
   Content-type: Message/CPIM

   From: Juliet Capulet <im:juliet@example.com>
   To: Romeo Montague <im:romeo@example.net>
   DateTime: 2003-12-09T23:45:36.66Z
   Subject: Imploring

   Content-type: text/plain; charset=utf-8
   Content-ID: <1234567890@example.com>

   Wherefore art thou, Romeo?
   --next
   Content-Type: application/pkcs7-signature
   Content-Disposition: attachment;handling=required;filename=smime.p7s

   [signed body part]

   --next--
   ]]>
     </e2e>
   </message>


4. Securing Presence

   In order to encrypt presence information, a sending entity MUST use
   the following procedure:

   1.  Generate an "application/pidf+xml" object as defined in [PIDF].

   2.  Encrypt and/or sign the "application/pidf+xml" object as
       specified in Requirement 3 of Section 2 above.

   3.  Provide the resulting [SMIME] object within a CDATA section of an
       <e2e/> child of a <presence/> stanza, where the <e2e/> element is
       qualified by the 'urn:ietf:params:xml:ns:xmpp-e2e' namespace.
       The <presence/> stanza MUST include a 'to' attribute, i.e., it
       must be an instance of directed presence as defined in [XMPP-IM].





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   Example 3: Sender generates "application/pidf+xml" object:

   <?xml version="1.0" encoding="UTF-8"?>
   <presence xmlns="urn:ietf:params:xml:ns:pidf"
             xmlns:im="urn:ietf:params:xml:ns:pidf:im"
             entity="pres:juliet@example.com">
     <tuple id="h40zny"
       <status>
         <basic>open</basic>
         <im:im>away</im:im>
       </status>
       <note xml:lang="en">retired to the chamber</note>
       <timestamp>2003-12-09T23:53:11.31</timestamp>
     </tuple>
   </presence>

   Example 4: Sender generates signed presence (the 'from' address on
   the XMPP presence stanza is stamped by sender's server):

   <presence to='romeo@example.net/orchard'>
     <e2e xmlns='urn:ietf:params:xml:ns:xmpp-e2e'>
   <![CDATA[
   Content-Type: multipart/signed; boundary=next;
                 micalg=sha1;
                 protocol=application/pkcs7-signature

   --next
   Content-type: application/pidf+xml
   Content-ID: <2345678901@example.com>

   <xml version="1.0" encoding="UTF-8"?>
   <presence xmlns="urn:ietf:params:xml:ns:pidf"
             xmlns:im="urn:ietf:params:xml:ns:pidf:im"
             entity="pres:juliet@example.com">
     <tuple id="hr0zny">
       <status>
         <basic>open</basic>
         <im:im>away</im:im>
       </status>
       <note xml:lang="en">retired to the chamber</note>
       <timestamp>2003-12-09T23:53:11.31Z</timestamp>
     </tuple>
   </presence>
   --next
   Content-Type: application/pkcs7-signature
   Content-Disposition: attachment;handling=required;filename=smime.p7s

   [signed body part]



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   --next--
   ]]>
     </e2e>
   </presence>


5. Securing Arbitrary XMPP Data

   The foregoing sections of this memo describe how to secure "least
   common denominator" messaging and presence data of the kind that can
   be directly translated into the MSGFMT or PIDF formats.  However,
   XMPP possesses a third base-level stanza type (<iq/>) in addition to
   <message/> and <presence/>, as well as the ability to include
   extended XML data within arbitrary child elements of the three core
   stanza types.  Therefore it would be desirable to secure such data if
   possible.

   Because [MSGFMT] specifies the ability to encapsulate any MIME type,
   the approach taken in this memo is to include arbitrary XMPP data in
   a new MIME type, "application/xmpp+xml".  The root element for this
   MIME type is <xmpp/>, and the root element MUST contain one and only
   one child element, corresponding to one of the XMPP stanza types
   (i.e., message, presence, or iq) if the default namespace is
   'jabber:client' or 'jabber:server' as defined in [XMPP-CORE].

   The following examples illustrate the structure of the "application/
   xmpp+xml" MIME type.

   Example 5: Message stanza with extended data contained in
   "application/xmpp+xml" MIME type:

   <?xml version='1.0' encoding='UTF-8'?>
   <xmpp xmlns='jabber:client'>
     <message
         from='iago@example.com/pda'
         to='emilia@example.com/cell'>
       <body>
         I told him what I thought, and told no more
         Than what he found himself was apt and true.
       </body>
       <evil xmlns='http://jabber.org/protocol/evil'/>
     </message>
   </xmpp>

   Example 6: Presence stanza with extended data contained in
   "application/xmpp+xml" MIME type:

   <?xml version='1.0' encoding='UTF-8'?>



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   <xmpp xmlns='jabber:client'>
     <presence from='iago@example.com/pda'>
       <show>dnd</show>
       <status>Fomenting dissension</status>
       <evil xmlns='http://jabber.org/protocol/evil'/>
     </presence>
   </xmpp>

   Example 7: IQ stanza with extended data contained in "application/
   xmpp+xml" MIME type:

   <?xml version='1.0' encoding='UTF-8'?>
   <xmpp xmlns='jabber:client'>
     <iq type='result'
         from='iago@example.com/pda'
         to='emilia@example.com/cell'
         id='evil1'>
       <query xmlns='jabber:iq:version'>
         <name>Stabber</name>
         <version>666</version>
         <os>FiendOS</os>
       </query>
       <evil xmlns='http://jabber.org/protocol/evil'/>
     </iq>
   </xmpp>


6. Rules for S/MIME Generation and Handling

6.1 Certificate Enrollment

   [SMIME] does not specify how to obtain a certificate from a
   certificate authority, but instead mandates that every sending agent
   must already have a certificate.  The PKIX Working Group has, at the
   time of this writing, produced two separate standards for certificate
   enrollment: [CMP] and [CMC].  Which method to use for certificate
   enrollment is outside the scope of this memo.

6.2 Certificate Retrieval

   A receiving agent MUST provide some certificate retrieval mechanism
   in order to gain access to certificates for recipients of digital
   envelopes.  This memo does not cover how S/MIME agents handle
   certificates, only what they do after a certificate has been
   validated or rejected.  S/MIME certification issues are covered in
   [CERT].

   At a minimum, for initial S/MIME deployment, a user agent could



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   automatically generate a message to an intended recipient requesting
   that recipient's certificate in a signed return message.  Receiving
   and sending agents SHOULD also provide a mechanism to allow a user to
   "store and protect" certificates for correspondents in such a way so
   as to guarantee their later retrieval.

6.3 Certificate Names

   End-entity certificates used by XMPP entities in the context of this
   memo SHOULD contain a valid instant messaging and presence address.
   The address SHOULD be specified as both an 'im:' URI (for instant
   messaging, as defined in [CPIM]) and a 'pres:' URI (for presence, as
   defined in [CPP]); each of these URIs SHOULD be specified in a
   separate GeneralName entry of type uniformResourceIdentifier inside
   the subjectAltName (i.e., two separate entries).  Information in the
   subject distinguished name SHOULD be ignored.

   Each URI MUST be of the form <im:address> or <pres:address>, where
   the "address" portion is an XMPP address (also referred to as a
   Jabber Identifier or JID) as defined in [XMPP-CORE], prepended with
   the 'im:' or 'pres:' URI scheme.  The address SHOULD be of the form
   <node@domain> (i.e., a "bare JID"), although any valid JID form MAY
   be used.

   The value of the JID contained in the XMPP 'from' attribute SHOULD
   match the JID provided in the signer's certificate, with the
   exception that the resource identifier portion of the JID contained
   in the 'from' attribute SHOULD be ignored for matching purposes.

   Receiving agents SHOULD check that sending JID matches a JID provided
   in the signer's certificate, with the exception that the resource
   identifier portion of the JID contained in the 'from' attribute MAY
   be ignored for matching purposes.  A receiving agent SHOULD provide
   some explicit alternate processing of the message if this comparison
   fails, which may be to display a message that shows the recipient the
   addresses in the certificate or other certificate details.

   The subject alternative name extension is used in S/MIME as the
   preferred means to convey the instant messaging and presence address
   that corresponds to the entity for this certificate.  Any instant
   messaging or presence address present in the certificate SHOULD be
   encoded using the otherName choice of the subjectAltName type along
   with a type-id of "xmpp" (as these terms are profiled in [X509]).

6.4 Transfer Encoding

   Because it is expected that XMPP applications will not interface with
   older 7-bit systems, the transfer encoding (as defined in Section



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   3.1.2 of [SMIME]) MUST be "binary".

6.5 Attachment of Signatures

   Sending agents SHOULD attach a signature to each encrypted message or
   presence stanza. If a signature is attached, a Content-Disposition
   header field (as defined in [DISP]) SHOULD be included to specify how
   the signature is to be handled by the receiving application.

6.6 Inclusion of Certificates

   If the sender and recipient are involved in an active messaging
   session over a period of time, the sending agent SHOULD include the
   sender's certificate along with at least one encrypted message stanza
   every five minutes. Outside the context of an active messaging
   session, the sending agent SHOULD include the sender's certificate
   along with each encrypted message stanza.  A sending agent MAY
   include the sender's certificate along with each encrypted presence
   stanza.  However, a sending agent SHOULD NOT include a certificate
   more than once every five minutes.

6.7 Order of Signing and Encrypting

   If a stanza is both signed and encrypted, it SHOULD be signed first,
   then encrypted.

6.8 Checking of Timestamps

   Timestamps are included in "Message/CPIM" and "application/pidf+xml"
   objects to help prevent replay attacks.  All timestamps MUST conform
   to [DATETIME] and be presented as UTC with no offset, including
   fractions of a second as appropriate.  Absent a local adjustment to
   the sending application's perceived time or the underlying clock
   time, the sending application MUST ensure that the timestamps it
   sends to the receiver increase monotonically (if necessary by
   incrementing the seconds fraction in the timestamp if the clock
   returns the same time for multiple requests).  The following rules
   apply to the receiving application:

   o  it MUST verify that the timestamp received is within five minutes
      of the current time

   o  it SHOULD verify that the timestamp received is greater than any
      timestamp received in the last 10 minutes which passed the
      previous check

   o  if any of the foregoing checks fails, the timestamp SHOULD be
      presented to the receiving entity (human or via an API) marked as



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      "old timestamp", "future timestamp", or "decreasing timestamp"


6.9 Mandatory to Implement Technologies

   At a minimum, all implementations MUST support the following CMS
   algorithms as defined in [CMS-ALG]:

   for digest: SHA-1

   for signing: RSA

   for content encryption: AES


7. Secure Communications Through a Gateway

   A common method for achieving interoperability between two disparate
   services is through the use of a "gateway" that interprets the
   protocols of each service and translates them into the protocols of
   the other.  The CPIM specifications (specifically [MSGFMT] and [PIDF]
   define the common profiles to be used for interoperability between
   instant messaging and presence services that comply with [IMP-REQS].
   In the case of communications between an XMPP service and a non-XMPP
   service, we can visualize this relationship as follows:

   +-------------+        +-------------+        +------------+
   |             |        |             |        |            |
   |    XMPP     |        |  XMPP-CPIM  |        |  Non-XMPP  |
   |   Service   | <----> |   Gateway   | <----> |  Service   |
   |             |        |             |        |            |
   +-------------+        +-------------+        +------------+

   The end-to-end encryption method defined herein enables the exchange
   of encrypted and/or signed instant messages and presence through an
   XMPP-CPIM gateway.  In particular:

   o  When a gateway receives a secured XMPP message or presence stanza
      from the XMPP service that is addressed to a user on the non-XMPP
      service, it MUST remove the XMPP "wrapper" (everything down to and
      including the <e2e> and </e2e> tags) in order to reveal the
      multipart S/MIME object, then route the object to the non-XMPP
      service (first wrapping it in the protocol used by the non-XMPP
      service if necessary).

   o  When a gateway receives a secured non-XMPP instant message or
      presence document from the non-XMPP service that is addressed to a
      user on the XMPP service, it MUST remove the non-XMPP "wrapper"



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      (if any) in order to reveal the multipart S/MIME object, wrap the
      object in an XMPP message or presence "wrapper" (including the
      <e2e> and </e2e> tags), and then route the XMPP stanza to the XMPP
      service.

   The wrapped S/MIME object MUST be immutable and MUST NOT be modified
   by an XMPP-CPIM gateway.

8. Security Considerations

   This entire memo discusses security.  Detailed security
   considerations for instant messaging and presence protocols are given
   in [IMP-REQS] (Sections 5.1 through 5.4), and for XMPP in particular
   are given in [XMPP-CORE] (Sections 12.1 through 12.6).

   The end-to-end security method defined here MAY result in exchanging
   secured instant messages and presence information through a gateway
   that implements the CPIM specifications.  Such a gateway MUST be
   compliant with the minimum security requirements of the instant
   messaging and presence protocols with which it interfaces.

9. IANA Considerations

9.1 Content-type Registration for "application/xmpp+xml"

   To: ietf-types@iana.org

   Subject: Registration of MIME media type application/xmpp+xml

   MIME media type name: application

   MIME subtype name: xmpp+xml

   Required parameters: (none)

   Optional parameters: charset Indicates the character encoding of the
      enclosed XML; the default encoding is UTF-8.

   Encoding considerations: Contains XML, which can employ 8-bit
      characters, depending on the character encoding used.

   Security considerations: Contains a message, presence information, or
      IQ (request-response) data in XMPP, which may be considered
      private.  Appropriate precautions should be adopted to limit
      disclosure of this information.






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   Interoperability considerations: (none)

   Specification: XXXX

   Applications which use this media type: XMPP-compliant instant
      messaging and presence systems.

   Additional information: (none)

   Person and email address to contact for further information: IETF,
      XMPP Working Group, <xmppwg@jabber.org>

   Intended usage: COMMON

   Author/Change controller: IETF, XMPP Working Group


9.2 XML Namespace Name for e2e Data in XMPP

   A URN sub-namespace for signed and encrypted content in the
   Extensible Messaging and Presence Protocol (XMPP) is defined as
   follows. (This namespace name adheres to the format defined in
   [XML-REG].)

   URI: urn:ietf:params:xml:ns:xmpp-e2e

   Specification: XXXX

   Description: This is the XML namespace name for signed and encrypted
      content in the Extensible Messaging and Presence Protocol as
      defined by XXXX.

   Registrant Contact: IETF, XMPP Working Group, <xmppwg@jabber.org>

Normative References

   [CERT]     Ramsdell, B., "S/MIME Version 3 Certificate Handling", RFC
              2632, June 1999.

   [CMC]      Blaze, M., Ioannidis, J. and A. Keromytis, "DSA and RSA
              Key and Signature Encoding for the KeyNote Trust
              Management System", RFC 2792, March 2000.

   [CMP]      Adams, C. and S. Farrell, "Internet X.509 Public Key
              Infrastructure Certificate Management Protocols", RFC
              2510, March 1999.

   [CMS]      Housley, R., "Cryptographic Message Syntax (CMS)", RFC



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              3369, August 2002.

   [CMS-ALG]  Housley, R., "Cryptographic Message Syntax (CMS)
              Algorithms", RFC 3370, August 2002.

   [CPIM]     Crocker, D. and J. Peterson, "Common Profile for Instant
              Messaging (CPIM)", draft-ietf-impp-im-03 (work in
              progress), May 2003.

   [CPP]      Crocker, D. and J. Peterson, "Common Profile for Presence
              (CPP)", draft-ietf-impp-pres-03 (work in progress), May
              2003.

   [DATETIME]
              Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, July 2002.

   [DISP]     Troost, R., Dorner, S. and K. Moore, "Communicating
              Presentation Information in Internet Messages: The
              Content-Disposition Header Field", RFC 2183, August 1997.

   [IMP-MODEL]
              Day, M., Rosenberg, J. and H. Sugano, "A Model for
              Presence and Instant Messaging", RFC 2778, February 2000,
              <http://www.ietf.org/rfc/rfc2778.txt>.

   [IMP-REQS]
              Day, M., Aggarwal, S. and J. Vincent, "Instant Messaging /
              Presence Protocol Requirements", RFC 2779, February 2000.

   [MSGFMT]   Atkins, D. and G. Klyne, "Common Presence and Instant
              Messaging: Message Format", draft-ietf-impp-cpim-msgfmt-08
              (work in progress), January 2003.

   [MULTI]    Galvin, J., Murphy, S., Crocker, S. and N. Freed,
              "Security Multiparts for MIME: Multipart/Signed and
              Multipart/Encrypted", RFC 1847, October 1995.

   [PIDF]     Fujimoto, S., Sugano, H., Klyne, G., Bateman, A., Carr, W.
              and J. Peterson, "Presence Information Data Format",
              draft-ietf-impp-cpim-pidf-08 (work in progress), May 2003.

   [SMIME]    Ramsdell, B., "S/MIME Version 3 Message Specification",
              RFC 2633, June 1999.

   [TERMS]    Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.




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   [X509]     Housley, R., Polk, W., Ford, W. and D. Solo, "Internet
              X.509 Public Key Infrastructure Certificate and
              Certificate Revocation List (CRL) Profile", RFC 3280,
              April 2002.

   [XMPP-CORE]
              Saint-Andre, P., "XMPP Core", draft-ietf-xmpp-core-21
              (work in progress), December 2003.

   [XMPP-IM]  Saint-Andre, P., "XMPP Instant Messaging",
              draft-ietf-xmpp-im-20 (work in progress), December 2003.

Informative References

   [XML-REG]  Mealling, M., "The IANA XML Registry",
              draft-mealling-iana-xmlns-registry-05 (work in progress),
              June 2003.

   [XMPP-CPIM]
              Saint-Andre, P., "Mapping the Extensible Messaging and
              Presence Protocol (XMPP) to Common Presence and Instant
              Messaging (CPIM)", draft-ietf-xmpp-cpim-03 (work in
              progress), November 2003.


Author's Address

   Peter Saint-Andre
   Jabber Software Foundation

   EMail: stpeter@jabber.org

Appendix A. Schema for urn:ietf:params:xml:ns:xmpp-e2e

   The following XML schema is descriptive, not normative.

   <?xml version='1.0' encoding='UTF-8'?>

   <xs:schema
       xmlns:xs='http://www.w3.org/2001/XMLSchema'
       targetNamespace='urn:ietf:params:xml:ns:xmpp-e2e'
       xmlns='urn:ietf:params:xml:ns:xmpp-e2e'
       elementFormDefault='qualified'>

     <xs:element name='e2e' type='xs:string'/>

   </xs:schema>




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Appendix B. Revision History

   Note to RFC Editor: please remove this entire appendix, and the
   corresponding entries in the table of contents, prior to publication.

B.1 Changes from draft-ietf-xmpp-e2e-06

   o  Specified use of SHA-1 for digest and AES for content encryption.

   o  Specified order of signing then encrypting.

   o  Specified format and checking of timestamps.

   o  Clarified use of subjectAltName field, where the GeneralName
      content is a URI of the form im:user@host and pres:user@host.

   o  Clarified circumstances under which certificates should be
      attached.

   o  Added Content-Disposition header field to examples.


B.2 Changes from draft-ietf-xmpp-e2e-05

   o  Addressed I-D nits and RFC Editor formatting.


B.3 Changes from draft-ietf-xmpp-e2e-04

   o  Added text about instant inbox addresses.


B.4 Changes from draft-ietf-xmpp-e2e-03

   o  Specified that S/MIME multipart objects are enclosed in a CDATA
      section.

   o  Changed "text/xml" to "text/plain" for message examples.

   o  Specified must-implement technologies, transfer encodings,
      certificate enrollment, certificate retrieval, and certificate
      names (including subjectAltName for JIDs).

   o  Specified requirements regarding attachment of signatures and
      inclusion of certificates.

   o  Fixed some small terminological errors.




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B.5 Changes from draft-ietf-xmpp-e2e-02

   o  Completely revised to use formats defined in the CPIM
      specifications, S/MIME only, etc.


B.6 Changes from draft-ietf-xmpp-e2e-01

   o  Removed old Section 6 (Signalling Support via Presence) -- the
      ability to sign broadcasted presence made it redundant.

   o  Made small editorial changes to address RFC Editor requirements.


B.7 Changes from draft-ietf-xmpp-e2e-00

   o  Added support for all stanza types.

   o  Specified that the full stanza is encrypted.

   o  Added support for S/MIME in addition to OpenPGP.

   o  Specified that encrypted presence must be directed to a specific
      recipient.

   o  Specified order of encrypting and signing.

   o  Added support for signing broadcasted presence.

   o  Added IANA considerations.

   o  Changed namespace to 'urn:ietf:params:xml:ns:xmpp-e2e'.

   o  Added XML schema.

















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   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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