rfc9734.original.xml   rfc9734.xml 
<?xml version='1.0' encoding='utf-8'?> <?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE rfc [ <!DOCTYPE rfc [
<!ENTITY nbsp "&#160;"> <!ENTITY nbsp "&#160;">
<!ENTITY zwsp "&#8203;"> <!ENTITY zwsp "&#8203;">
<!ENTITY nbhy "&#8209;"> <!ENTITY nbhy "&#8209;">
<!ENTITY wj "&#8288;"> <!ENTITY wj "&#8288;">
]> ]>
<?xml-stylesheet type="text/xsl" href="rfc2629.xslt" ?> <rfc xmlns:xi="http://www.w3.org/2001/XInclude" ipr="trust200902" docName="draft
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<rfc xmlns:xi="http://www.w3.org/2001/XInclude" ipr="trust200902" docName="draft s="true" version="3" xml:lang="en">
-ietf-lamps-im-keyusage-04" category="std" consensus="true" submissionType="IETF
" tocInclude="true" sortRefs="true" symRefs="true" version="3">
<!-- xml2rfc v2v3 conversion 3.23.2 -->
<front> <front>
<title abbrev="extendedKeyUsage for IM URIs">X.509 Certificate Extended Key Usage (EKU) for Instant Messaging URIs</title> <title abbrev="extendedKeyUsage for IM URIs">X.509 Certificate Extended Key Usage (EKU) for Instant Messaging URIs</title>
<seriesInfo name="Internet-Draft" value="draft-ietf-lamps-im-keyusage-04"/> <seriesInfo name="RFC" value="9734"/>
<author fullname="Rohan Mahy"> <author fullname="Rohan Mahy">
<organization>Rohan Mahy Consulting Services</organization> <organization>Rohan Mahy Consulting Services</organization>
<address> <address>
<email>rohan.ietf@gmail.com</email> <email>rohan.ietf@gmail.com</email>
</address> </address>
</author> </author>
<date year="2024" month="December" day="09"/> <date year="2025" month="February"/>
<area>SEC</area> <area>SEC</area>
<workgroup>LAMPS WG</workgroup> <workgroup>lamps</workgroup>
<keyword>x.509</keyword> <keyword>x.509</keyword>
<keyword>certificate</keyword> <keyword>certificate</keyword>
<keyword>extended key usage</keyword> <keyword>extended key usage</keyword>
<keyword>eku</keyword> <keyword>eku</keyword>
<keyword>instant messaging</keyword> <keyword>instant messaging</keyword>
<keyword>im URI</keyword> <keyword>im URI</keyword>
<keyword>mimi URL</keyword> <keyword>mimi URL</keyword>
<abstract> <abstract>
<?line 61?>
<t>RFC 5280 specifies several extended key purpose identifiers <t>RFC 5280 specifies several extended key purpose identifiers
(KeyPurposeIds) for X.509 certificates. This document defines (KeyPurposeIds) for X.509 certificates. This document defines
Instant Messaging (IM) identity KeyPurposeId for inclusion in an Instant Messaging (IM) identity KeyPurposeId for inclusion in
the Extended Key Usage (EKU) extension of X.509 v3 public key the Extended Key Usage (EKU) extension of X.509 v3 public key
certificates</t> certificates</t>
</abstract> </abstract>
<note removeInRFC="true">
<name>About This Document</name>
<t>
The latest revision of this draft can be found at <eref target="https://
rohanmahy.github.io/mahy-lamps-im-keyusage/draft-ietf-lamps-im-keyusage.html"/>.
Status information for this document may be found at <eref target="https
://datatracker.ietf.org/doc/draft-ietf-lamps-im-keyusage/"/>.
</t>
<t>
Discussion of this document takes place on the
LAMPS WG Working Group mailing list (<eref target="mailto:lamps@ietf.org
"/>),
which is archived at <eref target="https://mailarchive.ietf.org/arch/bro
wse/lamps/"/>.
Subscribe at <eref target="https://www.ietf.org/mailman/listinfo/lamps/"
/>.
</t>
<t>Source for this draft and an issue tracker can be found at
<eref target="https://github.com/rohanmahy/mahy-lamps-im-keyusage"/>.</t
>
</note>
</front> </front>
<middle> <middle>
<?line 70?>
<section anchor="introduction"> <section anchor="introduction">
<name>Introduction</name> <name>Introduction</name>
<t>Instant Messaging (IM) systems using the Messaging Layer Security (MLS) <t>Instant Messaging (IM) systems using the Messaging Layer Security (MLS)
<xref target="RFC9420"/> protocol can incorporate per-client identity certificat e <xref target="RFC9420"/> protocol can incorporate per-client identity certificat e
credentials. A subjectAltName in these certificates can be an IM URI credentials. A subjectAltName in these certificates can be an IM URI
<xref target="RFC3860"/> or XMPP URI <xref target="RFC6121"/>, for example.</t> <xref target="RFC3860"/> or Extensible Messaging and Presence Protocol (XMPP) UR
<t>Organizations may be unwilling to issue certificates for Instant Messag I <xref target="RFC6121"/>, for example.</t>
e <t>Organizations may be unwilling to issue certificates for an IM
client using a general KeyPurposeId such as <tt>id-kp-serverAuth</tt> or client using a general KeyPurposeId, such as <tt>id-kp-serverAuth</tt> or
<tt>id-kp-clientAuth</tt>, because of the risk that such certificates could be <tt>id-kp-clientAuth</tt>, because of the risk that such certificates could be
abused in a cross-protocol attack.</t> abused in a cross-protocol attack.</t>
<t>An explanation of MLS credentials as they apply to Instant Messaging is <t>An explanation of MLS credentials as they apply to IM is
described in <xref target="I-D.barnes-mimi-identity-arch"/>. These credentials a re described in <xref target="I-D.barnes-mimi-identity-arch"/>. These credentials a re
expected to be heavily used in the More Instant Messaging Interoperability expected to be heavily used in the More Instant Messaging Interoperability
(MIMI) Working Group.</t> (MIMI) Working Group.</t>
</section> </section>
<section anchor="conventions-and-definitions"> <section anchor="conventions-and-definitions">
<name>Conventions and Definitions</name> <name>Conventions and Definitions</name>
<t>The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14 <t>
>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>",
NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>RECO "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL NOT</bcp14>
MMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>", ",
"<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are to be i "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>",
nterpreted as "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
described in BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and "<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are to
only when, they be
appear in all capitals, as shown here.</t> interpreted as described in BCP&nbsp;14 <xref target="RFC2119"/> <xref
<?line -18?> target="RFC8174"/> when, and only when, they appear in all capitals, as
shown here.
</t>
</section>
</section>
<section anchor="the-im-uri-extended-key-usage"> <section anchor="the-im-uri-extended-key-usage">
<name>The IM URI Extended Key Usage</name> <name>The IM URI EKU</name>
<t>This specification defines the KeyPurposeId id-kp-imUri, which <t>This specification defines the KeyPurposeId <tt>id-kp-imUri</tt>, which
may be included in certificates used to prove the identity of an Instant may be
Messaging client. included in certificates used to prove the identity of an IM client. This
This EKU extension <bcp14>MAY</bcp14>, at the option of the certificate issuer, EKU extension <bcp14>MAY</bcp14>, at the option
be either of the certificate issuer, be either critical or non-critical.</t>
critical or non-critical.</t>
<artwork><![CDATA[ <sourcecode type="asn.1"><![CDATA[
id-kp OBJECT IDENTIFIER ::= { id-kp OBJECT IDENTIFIER ::= {
iso(1) identified-organization(3) dod(6) internet(1) iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) kp(3) } security(5) mechanisms(5) pkix(7) kp(3) }
id-kp-imUri OBJECT IDENTIFIER ::= { id-kp TBD1 } id-kp-imUri OBJECT IDENTIFIER ::= { id-kp 40 }]]></sourcecode>
]]></artwork>
</section> </section>
<section anchor="security-considerations"> <section anchor="security-considerations">
<name>Security Considerations</name> <name>Security Considerations</name>
<t>The Security Considerations of <xref target="RFC5280"/> are applicable
to this <t>The security considerations of <xref target="RFC5280"/> are applicable
document. This extended key purpose does not introduce new security to this
document. The <tt>id-kp-imUri</tt> extended key purpose does not introduce new
security
risks but instead reduces existing security risks by providing means risks but instead reduces existing security risks by providing means
to identify if the certificate is generated to sign IM identity credentials. to identify if the certificate is generated to sign IM identity credentials.
Issuers <bcp14>SHOULD NOT</bcp14> set the <tt>id-kp-imUri</tt> extended key purp ose and an Issuers <bcp14>SHOULD NOT</bcp14> set the <tt>id-kp-imUri</tt> extended key purp ose and an
<tt>id-kp-clientAuth</tt> or <tt>id-kp-serverAuth</tt> extended key purpose, as that would <tt>id-kp-clientAuth</tt> or <tt>id-kp-serverAuth</tt> extended key purpose: tha t would
defeat the improved specificity offered by having an <tt>id-kp-imUri</tt> extend ed key defeat the improved specificity offered by having an <tt>id-kp-imUri</tt> extend ed key
purpose.</t> purpose.</t>
</section> </section>
<section anchor="iana-considerations"> <section anchor="iana-considerations">
<name>IANA Considerations</name> <name>IANA Considerations</name>
<t>IANA is requested to register the following OIDs in the "SMI Security <t>IANA has registered the following OID in the "SMI Security
for PKIX Extended Key Purpose" registry (1.3.6.1.5.5.7.3). These for PKIX Extended Key Purpose" registry (1.3.6.1.5.5.7.3). This
OIDs are defined in Section 4.</t> OID is defined in <xref target="the-im-uri-extended-key-usage"/>.</t>
<table> <table>
<thead> <thead>
<tr> <tr>
<th align="left">Decimal</th> <th align="left">Decimal</th>
<th align="left">Description</th> <th align="left">Description</th>
<th align="left">References</th> <th align="left">References</th>
</tr> </tr>
</thead> </thead>
<tbody> <tbody>
<tr> <tr>
<td align="left">TBD1</td> <td align="left">40</td>
<td align="left">id-kp-imUri</td> <td align="left">id-kp-imUri</td>
<td align="left">This-RFC</td> <td align="left">RFC 9734</td>
</tr> </tr>
</tbody> </tbody>
</table> </table>
<t>IANA is also requested to register the following ASN.1 <xref target="IT U.X690.2021"/> <t>IANA has also registered the following ASN.1 <xref target="ITU.X690.202 1"/>
module OID in the "SMI Security for PKIX Module Identifier" registry (1.3.6.1.5. 5.7.0). This OID is defined in <xref target="asn1-module"/>.</t> module OID in the "SMI Security for PKIX Module Identifier" registry (1.3.6.1.5. 5.7.0). This OID is defined in <xref target="asn1-module"/>.</t>
<table> <table>
<thead> <thead>
<tr> <tr>
<th align="left">Decimal</th> <th align="left">Decimal</th>
<th align="left">Description</th> <th align="left">Description</th>
<th align="left">References</th> <th align="left">References</th>
</tr> </tr>
</thead> </thead>
<tbody> <tbody>
<tr> <tr>
<td align="left">TBD2</td> <td align="left">113</td>
<td align="left">id-mod-im-eku</td> <td align="left">id-mod-im-eku</td>
<td align="left">This-RFC</td> <td align="left">RFC 9734</td>
</tr> </tr>
</tbody> </tbody>
</table> </table>
</section> </section>
</middle> </middle>
<back> <back>
<displayreference target="I-D.barnes-mimi-identity-arch" to="E2E-IDENTITY"/>
<references anchor="sec-combined-references"> <references anchor="sec-combined-references">
<name>References</name> <name>References</name>
<references anchor="sec-normative-references"> <references anchor="sec-normative-references">
<name>Normative References</name> <name>Normative References</name>
<reference anchor="ITU.X690.2021">
<reference anchor="ITU.X690.2021" target="https://www.itu.int/rec/T-REC-
X.690">
<front> <front>
<title>Information Technology - ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)</title> <title>Information Technology - ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)</title>
<author> <author>
<organization>International Telecommunications Union</organization > <organization>ITU-T</organization>
</author> </author>
<date year="2021"/> <date month="February" year="2021"/>
</front> </front>
<seriesInfo name="ITU-T" value="Recommendation X.690"/> <seriesInfo name="ITU-T" value="Recommendation X.690"/>
<seriesInfo name="ISO/IEC" value="8825-1-2021"/>
</reference> </reference>
<reference anchor="ITU.X680.2021">
<reference anchor="ITU.X680.2021" target="https://www.itu.int/rec/T-REC-
X.680">
<front> <front>
<title>Information Technology - Abstract Syntax Notation One (ASN.1) : Specification of basic notation</title> <title>Information Technology - Abstract Syntax Notation One (ASN.1) : Specification of basic notation</title>
<author> <author>
<organization>International Telecommunications Union</organization > <organization>ITU-T</organization>
</author> </author>
<date year="2021"/> <date month="February" year="2021"/>
</front>
<seriesInfo name="ITU-T" value="Recommendation X.680"/>
</reference>
<reference anchor="RFC2119">
<front>
<title>Key words for use in RFCs to Indicate Requirement Levels</tit
le>
<author fullname="S. Bradner" initials="S." surname="Bradner"/>
<date month="March" year="1997"/>
<abstract>
<t>In many standards track documents several words are used to sig
nify the requirements in the specification. These words are often capitalized. T
his document defines these words as they should be interpreted in IETF documents
. This document specifies an Internet Best Current Practices for the Internet Co
mmunity, and requests discussion and suggestions for improvements.</t>
</abstract>
</front>
<seriesInfo name="BCP" value="14"/>
<seriesInfo name="RFC" value="2119"/>
<seriesInfo name="DOI" value="10.17487/RFC2119"/>
</reference>
<reference anchor="RFC8174">
<front>
<title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</ti
tle>
<author fullname="B. Leiba" initials="B." surname="Leiba"/>
<date month="May" year="2017"/>
<abstract>
<t>RFC 2119 specifies common key words that may be used in protoco
l specifications. This document aims to reduce the ambiguity by clarifying that
only UPPERCASE usage of the key words have the defined special meanings.</t>
</abstract>
</front>
<seriesInfo name="BCP" value="14"/>
<seriesInfo name="RFC" value="8174"/>
<seriesInfo name="DOI" value="10.17487/RFC8174"/>
</reference>
<reference anchor="RFC5280">
<front>
<title>Internet X.509 Public Key Infrastructure Certificate and Cert
ificate Revocation List (CRL) Profile</title>
<author fullname="D. Cooper" initials="D." surname="Cooper"/>
<author fullname="S. Santesson" initials="S." surname="Santesson"/>
<author fullname="S. Farrell" initials="S." surname="Farrell"/>
<author fullname="S. Boeyen" initials="S." surname="Boeyen"/>
<author fullname="R. Housley" initials="R." surname="Housley"/>
<author fullname="W. Polk" initials="W." surname="Polk"/>
<date month="May" year="2008"/>
<abstract>
<t>This memo profiles the X.509 v3 certificate and X.509 v2 certif
icate revocation list (CRL) for use in the Internet. An overview of this approac
h and model is provided as an introduction. The X.509 v3 certificate format is d
escribed in detail, with additional information regarding the format and semanti
cs of Internet name forms. Standard certificate extensions are described and two
Internet-specific extensions are defined. A set of required certificate extensi
ons is specified. The X.509 v2 CRL format is described in detail along with stan
dard and Internet-specific extensions. An algorithm for X.509 certification path
validation is described. An ASN.1 module and examples are provided in the appen
dices. [STANDARDS-TRACK]</t>
</abstract>
</front> </front>
<seriesInfo name="RFC" value="5280"/> <seriesInfo name="ITU-T Recommendation" value="X.680"/>
<seriesInfo name="DOI" value="10.17487/RFC5280"/> <seriesInfo name="ISO/IEC" value="8824-1:2021"/>
</reference> </reference>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.2
119.xml"/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8
174.xml"/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.5
280.xml"/>
</references> </references>
<references anchor="sec-informative-references"> <references anchor="sec-informative-references">
<name>Informative References</name> <name>Informative References</name>
<reference anchor="RFC9420"> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9
<front> 420.xml"/>
<title>The Messaging Layer Security (MLS) Protocol</title> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.3
<author fullname="R. Barnes" initials="R." surname="Barnes"/> 860.xml"/>
<author fullname="B. Beurdouche" initials="B." surname="Beurdouche"/ <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6
> 121.xml"/>
<author fullname="R. Robert" initials="R." surname="Robert"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml3/reference.I-D.
<author fullname="J. Millican" initials="J." surname="Millican"/> barnes-mimi-identity-arch.xml"/>
<author fullname="E. Omara" initials="E." surname="Omara"/>
<author fullname="K. Cohn-Gordon" initials="K." surname="Cohn-Gordon
"/>
<date month="July" year="2023"/>
<abstract>
<t>Messaging applications are increasingly making use of end-to-en
d security mechanisms to ensure that messages are only accessible to the communi
cating endpoints, and not to any servers involved in delivering messages. Establ
ishing keys to provide such protections is challenging for group chat settings,
in which more than two clients need to agree on a key but may not be online at t
he same time. In this document, we specify a key establishment protocol that pro
vides efficient asynchronous group key establishment with forward secrecy (FS) a
nd post-compromise security (PCS) for groups in size ranging from two to thousan
ds.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="9420"/>
<seriesInfo name="DOI" value="10.17487/RFC9420"/>
</reference>
<reference anchor="RFC3860">
<front>
<title>Common Profile for Instant Messaging (CPIM)</title>
<author fullname="J. Peterson" initials="J." surname="Peterson"/>
<date month="August" year="2004"/>
<abstract>
<t>At the time this document was written, numerous instant messagi
ng protocols were in use, and little interoperability between services based on
these protocols has been achieved. This specification defines common semantics a
nd data formats for instant messaging to facilitate the creation of gateways bet
ween instant messaging services. [STANDARDS-TRACK]</t>
</abstract>
</front>
<seriesInfo name="RFC" value="3860"/>
<seriesInfo name="DOI" value="10.17487/RFC3860"/>
</reference>
<reference anchor="RFC6121">
<front>
<title>Extensible Messaging and Presence Protocol (XMPP): Instant Me
ssaging and Presence</title>
<author fullname="P. Saint-Andre" initials="P." surname="Saint-Andre
"/>
<date month="March" year="2011"/>
<abstract>
<t>This document defines extensions to core features of the Extens
ible Messaging and Presence Protocol (XMPP) that provide basic instant messaging
(IM) and presence functionality in conformance with the requirements in RFC 277
9. This document obsoletes RFC 3921. [STANDARDS-TRACK]</t>
</abstract>
</front>
<seriesInfo name="RFC" value="6121"/>
<seriesInfo name="DOI" value="10.17487/RFC6121"/>
</reference>
<reference anchor="I-D.barnes-mimi-identity-arch">
<front>
<title>Identity for E2E-Secure Communications</title>
<author fullname="Richard Barnes" initials="R." surname="Barnes">
<organization>Cisco</organization>
</author>
<author fullname="Rohan Mahy" initials="R." surname="Mahy">
<organization>Wire</organization>
</author>
<date day="23" month="October" year="2023"/>
<abstract>
<t> End-to-end (E2E) security is a critical property for modern
user
communications systems. E2E security protects users' communications
from tampering or inspection by intermediaries that are involved in
delivering those communcations from one logical endpoint to another.
In addition to the much-discussed E2E encryption systems, true E2E
security requires an identity mechanism that prevents the
communications provider from impersonating participants in a session,
as a way to gain access to the session. This document describes a
high-level architecture for E2E identity, identifying the critical
mechanisms that need to be specified.
</t>
</abstract>
</front>
<seriesInfo name="Internet-Draft" value="draft-barnes-mimi-identity-ar
ch-01"/>
</reference>
</references> </references>
</references> </references>
<?line 157?>
<section anchor="asn1-module"> <section anchor="asn1-module">
<name>ASN.1 Module</name> <name>ASN.1 Module</name>
<t>The following module adheres to ASN.1 specifications <xref target="ITU. X680.2021"/> and <t>The following module adheres to ASN.1 specifications <xref target="ITU. X680.2021"/> and
<xref target="ITU.X690.2021"/>.</t> <xref target="ITU.X690.2021"/>.</t>
<sourcecode type="asn1"><![CDATA[
<sourcecode type="asn.1"><![CDATA[
<CODE BEGINS> <CODE BEGINS>
IM-EKU IM-EKU
{ iso(1) identified-organization(3) dod(6) internet(1) { iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0) security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-im-eku (TBD2) } id-mod-im-eku (113) }
DEFINITIONS IMPLICIT TAGS ::= DEFINITIONS IMPLICIT TAGS ::=
BEGIN BEGIN
-- OID Arc -- OID Arc
id-kp OBJECT IDENTIFIER ::= id-kp OBJECT IDENTIFIER ::=
{ iso(1) identified-organization(3) dod(6) internet(1) { iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) kp(3) } security(5) mechanisms(5) pkix(7) kp(3) }
-- Extended Key Usage Values -- Extended Key Usage Values
id-kp-imUri OBJECT IDENTIFIER ::= { id-kp TBD1 } id-kp-imUri OBJECT IDENTIFIER ::= { id-kp 40 }
END END
<CODE ENDS> <CODE ENDS>]]></sourcecode>
]]></sourcecode>
</section>
<section anchor="change-log">
<name>Change log</name>
<t>RFC Editor, please remove this section on publication.</t>
<ul spacing="normal">
<li>
<t>made Proposed Standard</t>
</li>
<li>
<t>added a <bcp14>MAY</bcp14> statement in Section 3</t>
</li>
<li>
<t>corrected typo in registration of the ASN.1 module (Thanks Sean!)</
t>
</li>
<li>
<t>updated author affiliation</t>
</li>
<li>
<t>added ASN.1 module</t>
</li>
<li>
<t>specified that eku is optionally critical</t>
</li>
</ul>
</section> </section>
<section numbered="false" anchor="acknowledgments"> <section numbered="false" anchor="acknowledgments">
<name>Acknowledgments</name> <name>Acknowledgments</name>
<t>Thanks to Sean Turner and Russ Housley for reviews, suggestions, <t>Thanks to <contact fullname="Sean Turner"/> and <contact
corrections, and encouragement.</t> fullname="Russ Housley"/> for reviews, suggestions, corrections, and
encouragement.</t>
</section> </section>
</back>
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</rfc> </rfc>
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