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Deprecating TLS 1.0 and TLS 1.1
draft-ietf-tls-oldversions-deprecate-12

The information below is for an old version of the document that is already published as an RFC.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 8996.
Authors Kathleen Moriarty , Stephen Farrell
Last updated 2021-03-25 (Latest revision 2021-01-21)
Replaces draft-moriarty-tls-oldversions-diediedie
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status Best Current Practice
Formats
Reviews
Additional resources Mailing list discussion
Stream WG state Submitted to IESG for Publication
Document shepherd Sean Turner
Shepherd write-up Show Last changed 2020-12-29
IESG IESG state Became RFC 8996 (Best Current Practice)
Action Holders
(None)
Consensus boilerplate Yes
Telechat date (None)
Responsible AD Benjamin Kaduk
Send notices to Sean Turner <sean@sn3rd.com>, Kathleen Moriarty <kathleen.moriarty.ietf@gmail.com>
IANA IANA review state IANA OK - No Actions Needed
IANA action state No IANA Actions
draft-ietf-tls-oldversions-deprecate-12
Internet Engineering Task Force                              K. Moriarty
Internet-Draft                                                  Dell EMC
Obsoletes: 5469 7507 (if approved)                            S. Farrell
Updates: 8422 8261 7568 7562 7525 7465            Trinity College Dublin
         7030 6750 6749 6739 6460 6614                  January 21, 2021
         6367 6353 6347 6176 6084 6083
         6042 6012 5953 5878 5734 5456
         5422 5415 5364 5281 5263 5238
         5216 5158 5091 5054 5049 5024
         5023 5019 5018 4992 4976 4975
         4964 4851 4823 4791 4785 4744
         4743 4732 4712 4681 4680 4642
         4616 4582 4540 4531 4513 4497
         4279 4261 4235 4217 4168 4162
         4111 4097 3983 3943 3903 3887
         3871 3856 3767 3749 3656 3568
         3552 3501 3470 3436 3329 3261
         (if approved)
Intended status: Best Current Practice
Expires: July 25, 2021

                    Deprecating TLSv1.0 and TLSv1.1
                draft-ietf-tls-oldversions-deprecate-12

Abstract

   This document, if approved, formally deprecates Transport Layer
   Security (TLS) versions 1.0 (RFC 2246) and 1.1 (RFC 4346).
   Accordingly, those documents (will be moved|have been moved) to
   Historic status.  These versions lack support for current and
   recommended cryptographic algorithms and mechanisms, and various
   government and industry profiles of applications using TLS now
   mandate avoiding these old TLS versions.  TLSv1.2 became the
   recommended version for IETF protocols in 2008, (subsequently being
   obsoleted by TLSv1.3 in 2018), providing sufficient time to
   transition away from older versions.  Removing support for older
   versions from implementations reduces the attack surface, reduces
   opportunity for misconfiguration, and streamlines library and product
   maintenance.

   This document also deprecates Datagram TLS (DTLS) version 1.0 (RFC
   4347), but not DTLS version 1.2, and there is no DTLS version 1.1.

   This document updates many RFCs that normatively refer to TLSv1.0 or
   TLSv1.1 as described herein.  This document also updates the best
   practices for TLS usage in RFC 7525 and hence is part of BCP 195.

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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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on July 25, 2021.

Copyright Notice

   Copyright (c) 2021 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
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  RFCs Updated  . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   5
   2.  Support for Deprecation . . . . . . . . . . . . . . . . . . .   5
   3.  SHA-1 Usage Problematic in TLSv1.0 and TLSv1.1  . . . . . . .   6
   4.  Do Not Use TLSv1.0  . . . . . . . . . . . . . . . . . . . . .   6
   5.  Do Not Use TLSv1.1  . . . . . . . . . . . . . . . . . . . . .   7
   6.  Updates to RFC 7525 . . . . . . . . . . . . . . . . . . . . .   8
   7.  Operational Considerations  . . . . . . . . . . . . . . . . .   8
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   9

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     11.2.  Informative References . . . . . . . . . . . . . . . . .  18
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .  22
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  24

1.  Introduction

   Transport Layer Security (TLS) versions 1.0 [RFC2246] and 1.1
   [RFC4346] were superseded by TLSv1.2 [RFC5246] in 2008, which has now
   itself been superseded by TLSv1.3 [RFC8446].  Datagram Transport
   Layer Security (DTLS) version 1.0 [RFC4347] was superseded by
   DTLSv1.2 [RFC6347] in 2012.  It is therefore timely to further
   deprecate TLSv1.0, TLSv1.1 and DTLSv1.0.  Accordingly, those
   documents (will be moved|have been moved) to Historic status.

   Technical reasons for deprecating these versions include:

   o  They require implementation of older cipher suites that are no
      longer desirable for cryptographic reasons, e.g., TLSv1.0 makes
      TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA mandatory to implement
   o  Lack of support for current recommended cipher suites, especially
      AEAD ciphers which are not supported prior to TLSv1.2.  Note:
      registry entries for no-longer-desirable ciphersuites remain in
      the registries, but many TLS registries are being updated through
      [RFC8447] which indicates that such entries are not recommended by
      the IETF.
   o  Integrity of the handshake depends on SHA-1 hash.
   o  Authentication of the peers depends on SHA-1 signatures.
   o  Support for four TLS protocol versions increases the likelihood of
      misconfiguration.
   o  At least one widely-used library has plans to drop TLSv1.1 and
      TLSv1.0 support in upcoming releases; products using such
      libraries would need to use older versions of the libraries to
      support TLSv1.0 and TLSv1.1, which is clearly undesirable.

   Deprecation of these versions is intended to assist developers as
   additional justification to no longer support older (D)TLS versions
   and to migrate to a minimum of (D)TLSv1.2.  Deprecation also assists
   product teams with phasing out support for the older versions, to
   reduce the attack surface and the scope of maintenance for protocols
   in their offerings.

1.1.  RFCs Updated

   This document updates the following RFCs that normatively reference
   TLSv1.0 or TLSv1.1 or DTLS1.0.  The update is to obsolete usage of
   these older versions.  Fallback to these versions is prohibited
   through this update.  Specific references to mandatory minimum
   protocol versions of TLSv1.0 or TLSv1.1 are replaced by TLSv1.2, and

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   references to minimum protocol version DTLSv1.0 are replaced by
   DTLSv1.2.  Statements that "TLSv1.0 is the most widely deployed
   version and will provide the broadest interoperability" are removed
   without replacement.

   [RFC8422] [RFC8261] [RFC7568] [RFC7562] [RFC7525] [RFC7465] [RFC7030]
   [RFC6750] [RFC6749] [RFC6739] [RFC6084] [RFC6083] [RFC6367] [RFC6353]
   [RFC6176] [RFC6042] [RFC6012] [RFC5878] [RFC5734] [RFC5456] [RFC5422]
   [RFC5415] [RFC5364] [RFC5281] [RFC5263] [RFC5238] [RFC5216] [RFC5158]
   [RFC5091] [RFC5054] [RFC5049] [RFC5024] [RFC5023] [RFC5019] [RFC5018]
   [RFC4992] [RFC4976] [RFC4975] [RFC4964] [RFC4851] [RFC4823] [RFC4791]
   [RFC4785] [RFC4732] [RFC4712] [RFC4681] [RFC4680] [RFC4642] [RFC4616]
   [RFC4582] [RFC4540] [RFC4531] [RFC4513] [RFC4497] [RFC4279] [RFC4261]
   [RFC4235] [RFC4217] [RFC4168] [RFC4162] [RFC4111] [RFC4097] [RFC3983]
   [RFC3943] [RFC3903] [RFC3887] [RFC3871] [RFC3856] [RFC3767] [RFC3749]
   [RFC3656] [RFC3568] [RFC3552] [RFC3501] [RFC3470] [RFC3436] [RFC3329]
   [RFC3261]

   The status of [RFC7562], [RFC6042], [RFC5456], [RFC5024], [RFC4540],
   and [RFC3656] will be updated with permission of the Independent
   Stream Editor.

   In addition these RFCs normatively refer to TLSv1.0 or TLSv1.1 and
   have already been obsoleted; they are still listed here and marked as
   updated by this document in order to reiterate that any usage of the
   obsolete protocol should still use modern TLS: [RFC5953] [RFC5101]
   [RFC5081] [RFC5077] [RFC4934] [RFC4572] [RFC4507] [RFC4492] [RFC4366]
   [RFC4347] [RFC4244] [RFC4132] [RFC3920] [RFC3734] [RFC3588] [RFC3546]
   [RFC3489] [RFC3316]

   Note that [RFC4642] has already been updated by [RFC8143], which
   makes an overlapping, but not quite identical, update as this
   document.

   [RFC6614] has a requirement for TLSv1.1 or later, although only makes
   an informative reference to [RFC4346].  This requirement is updated
   to be for TLSv1.2 or later.

   [RFC6460], [RFC4744], and [RFC4743] are already Historic; they are
   still listed here and marked as updated by this document in order to
   reiterate that any usage of the obsolete protocol should still use
   modern TLS.

   This document updates DTLS [RFC6347].  [RFC6347] had allowed for
   negotiating the use of DTLSv1.0, which is now forbidden.

   The DES and IDEA cipher suites specified in [RFC5469] were
   specifically removed from TLSv1.2 by [RFC5246]; since the only

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   versions of TLS for which their usage is defined are now Historic,
   RFC 5469 (will be|has been) moved to Historic as well.

   The version-fallback Signaling Cipher Suite Value specified in
   [RFC7507] was defined to detect when a given client and server
   negotiate a lower version of (D)TLS than their highest shared
   version.  TLSv1.3 ([RFC8446]) incorporates a different mechanism that
   achieves this purpose, via sentinel values in the ServerHello.Random
   field.  With (D)TLS versions prior to 1.2 fully deprecated, the only
   way for (D)TLS implementations to negotiate a lower version than
   their highest shared version would be to negotiate (D)TLSv1.2 while
   supporting (D)TLSv1.3; supporting (D)TLSv1.3 implies support for the
   ServerHello.Random mechanism.  Accordingly, the functionality from
   [RFC7507] has been superseded, and this document marks it as
   Obsolete.

1.2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Support for Deprecation

   Specific details on attacks against TLSv1.0 and TLSv1.1, as well as
   their mitigations, are provided in [NIST800-52r2], RFC 7457 [RFC7457]
   and other RFCs referenced therein.  Although mitigations for the
   current known vulnerabilities have been developed, any future issues
   discovered in old protocol versions might not be mitigated in older
   library versions when newer library versions do not support those old
   protocols.

   NIST for example has provided the following rationale, copied with
   permission from [NIST800-52r2], section 1.2 "History of TLS" (with
   references changed for RFC formatting).

      TLS 1.1, specified in [RFC4346], was developed to address
      weaknesses discovered in TLS 1.0, primarily in the areas of
      initialization vector selection and padding error processing.
      Initialization vectors were made explicit to prevent a certain
      class of attacks on the Cipher Block Chaining (CBC) mode of
      operation used by TLS.  The handling of padding errors was altered
      to treat a padding error as a bad message authentication code,
      rather than a decryption failure.  In addition, the TLS 1.1 RFC
      acknowledges attacks on CBC mode that rely on the time to compute
      the message authentication code (MAC).  The TLS 1.1 specification

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      states that to defend against such attacks, an implementation must
      process records in the same manner regardless of whether padding
      errors exist.  Further implementation considerations for CBC modes
      (which were not included in RFC4346 [RFC4346]) are discussed in
      Section 3.3.2.

      TLSv1.2, specified in RFC5246 [RFC5246], made several
      cryptographic enhancements, particularly in the area of hash
      functions, with the ability to use or specify the SHA-2 family
      algorithms for hash, MAC, and Pseudorandom Function (PRF)
      computations.  TLSv1.2 also adds authenticated encryption with
      associated data (AEAD) cipher suites.

      TLSv1.3, specified in TLSv1.3 [RFC8446], represents a significant
      change to TLS that aims to address threats that have arisen over
      the years.  Among the changes are a new handshake protocol, a new
      key derivation process that uses the HMAC-based Extract-and-Expand
      Key Derivation Function (HKDF), and the removal of cipher suites
      that use static RSA or DH key exchanges, the CBC mode of
      operation, or SHA-1.  The list of extensions that can be used with
      TLSv1.3 has been reduced considerably.

3.  SHA-1 Usage Problematic in TLSv1.0 and TLSv1.1

   The integrity of both TLSv1.0 and TLSv1.1 depends on a running SHA-1
   hash of the exchanged messages.  This makes it possible to perform a
   downgrade attack on the handshake by an attacker able to perform 2^77
   operations, well below the acceptable modern security margin.

   Similarly, the authentication of the handshake depends on signatures
   made using a SHA-1 hash or a not appreciably stronger concatenation
   of MD-5 and SHA-1 hashes, allowing the attacker to impersonate a
   server when it is able to break the severely weakened SHA-1 hash.

   Neither TLSv1.0 nor TLSv1.1 allow the peers to select a stronger hash
   for signatures in the ServerKeyExchange or CertificateVerify
   messages, making the only upgrade path the use of a newer protocol
   version.

   See [Bhargavan2016] for additional detail.

4.  Do Not Use TLSv1.0

   TLSv1.0 MUST NOT be used.  Negotiation of TLSv1.0 from any version of
   TLS MUST NOT be permitted.

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   Any other version of TLS is more secure than TLSv1.0.  While TLSv1.0
   can be configured to prevent some types of interception, using the
   highest version available is preferred.

   Pragmatically, clients MUST NOT send a ClientHello with
   ClientHello.client_version set to {03,01}. Similarly, servers MUST
   NOT send a ServerHello with ServerHello.server_version set to
   {03,01}. Any party receiving a Hello message with the protocol
   version set to {03,01} MUST respond with a "protocol_version" alert
   message and close the connection.

   Historically, TLS specifications were not clear on what the record
   layer version number (TLSPlaintext.version) could contain when
   sending ClientHello.  Appendix E of [RFC5246] notes that
   TLSPlaintext.version could be selected to maximize interoperability,
   though no definitive value is identified as ideal.  That guidance is
   still applicable; therefore, TLS servers MUST accept any value
   {03,XX} (including {03,00}) as the record layer version number for
   ClientHello, but they MUST NOT negotiate TLSv1.0.

5.  Do Not Use TLSv1.1

   TLSv1.1 MUST NOT be used.  Negotiation of TLSv1.1 from any version of
   TLS MUST NOT be permitted.

   Pragmatically, clients MUST NOT send a ClientHello with
   ClientHello.client_version set to {03,02}. Similarly, servers MUST
   NOT send a ServerHello with ServerHello.server_version set to
   {03,02}. Any party receiving a Hello message with the protocol
   version set to {03,02} MUST respond with a "protocol_version" alert
   message and close the connection.

   Any newer version of TLS is more secure than TLSv1.1.  While TLSv1.1
   can be configured to prevent some types of interception, using the
   highest version available is preferred.  Support for TLSv1.1 is
   dwindling in libraries and will impact security going forward if
   mitigations for attacks cannot be easily addressed and supported in
   older libraries.

   Historically, TLS specifications were not clear on what the record
   layer version number (TLSPlaintext.version) could contain when
   sending ClientHello.  Appendix E of [RFC5246] notes that
   TLSPlaintext.version could be selected to maximize interoperability,
   though no definitive value is identified as ideal.  That guidance is
   still applicable; therefore, TLS servers MUST accept any value
   {03,XX} (including {03,00}) as the record layer version number for
   ClientHello, but they MUST NOT negotiate TLSv1.1.

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6.  Updates to RFC 7525

   RFC7525 is BCP 195, "Recommendations for Secure Use of Transport
   Layer Security (TLS) and Datagram Transport Layer Security (DTLS)",
   which is the most recent best practice document for implementing TLS
   and was based on TLSv1.2.  At the time of publication, TLSv1.0 and
   TLSv1.1 had not yet been deprecated.  As such, BCP 195 is called out
   specifically to update text implementing the deprecation
   recommendations of this document.

   This document updates [RFC7525] Section 3.1.1 changing SHOULD NOT to
   MUST NOT as follows:

   o  Implementations MUST NOT negotiate TLS version 1.0 [RFC2246].

      Rationale: TLSv1.0 (published in 1999) does not support many
      modern, strong cipher suites.  In addition, TLSv1.0 lacks a per-
      record Initialization Vector (IV) for CBC-based cipher suites and
      does not warn against common padding errors.

   o  Implementations MUST NOT negotiate TLS version 1.1 [RFC4346].

      Rationale: TLSv1.1 (published in 2006) is a security improvement
      over TLSv1.0 but still does not support certain stronger cipher
      suites.

   This documents updates [RFC7525] Section 3.1.2 changing SHOULD NOT to
   MUST NOT as follows:

   o  Implementations MUST NOT negotiate DTLS version 1.0 [RFC4347],
      [RFC6347].

      Version 1.0 of DTLS correlates to version 1.1 of TLS (see above).

7.  Operational Considerations

   This document is part of BCP 195, and as such reflects the
   understanding of the IETF (at the time of its publication) as to the
   best practices for TLS and DTLS usage.

   Though TLSv1.1 has been obsolete since the publication of RFC 5246 in
   2008, and DTLSv1.0 has been obsolete since the publication of RFC
   6347 in 2012, there may remain some systems in operation that do not
   support (D)TLSv1.2 or higher.  Adopting the practices recommended by
   this document for any systems that need to communicate with the
   aforementioned class of systems will cause failure to interoperate.
   However, disregarding the recommendations of this document in order
   to continue to interoperate with the aforementioned class of systems

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   incurs some amount of risk.  The nature of the risks incurred by
   operating in contravention to the recommendations of this document
   are discussed in Sections 2 and 3, and knowledge of those risks
   should be used along with any potential mitigating factors and the
   risks inherent to updating the systems in question when deciding how
   quickly to adopt the recommendations specified in this document.

8.  Security Considerations

   This document deprecates two older TLS protocol versions and one
   older DTLS protocol version for security reasons already described.
   The attack surface is reduced when there are a smaller number of
   supported protocols and fallback options are removed.

9.  Acknowledgements

   Thanks to those that provided usage data, reviewed and/or improved
   this document, including: Michael Ackermann, David Benjamin, David
   Black, Deborah Brungard, Alan DeKok, Viktor Dukhovni, Julien Elie,
   Adrian Farrelll, Gary Gapinski, Alessandro Ghedini, Peter Gutmann,
   Jeremy Harris, Nick Hilliard, James Hodgkinson, Russ Housley, Hubert
   Kario, Benjamin Kaduk, John Klensin, Watson Ladd, Eliot Lear, Ted
   Lemon, John Mattsson, Keith Moore, Tom Petch, Eric Mill, Yoav Nir,
   Andrei Popov, Michael Richardson, Eric Rescorla, Rich Salz, Mohit
   Sethi, Yaron Sheffer, Rob Sayre, Robert Sparks, Barbara Stark, Martin
   Thomson, Sean Turner, Loganaden Velvindron, and Jakub Wilk.

   [[Note to RFC editor: At least Julien Elie's name above should have
   an accent on the first letter of the surname.  Please fix that and
   any others needing a similar fix if you can, I'm not sure the tooling
   I have now allows that.]]

10.  IANA Considerations

   [[This memo includes no request to IANA.]]

11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC2246]  Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
              RFC 2246, DOI 10.17487/RFC2246, January 1999,
              <https://www.rfc-editor.org/info/rfc2246>.

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   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              DOI 10.17487/RFC3261, June 2002,
              <https://www.rfc-editor.org/info/rfc3261>.

   [RFC3329]  Arkko, J., Torvinen, V., Camarillo, G., Niemi, A., and T.
              Haukka, "Security Mechanism Agreement for the Session
              Initiation Protocol (SIP)", RFC 3329,
              DOI 10.17487/RFC3329, January 2003,
              <https://www.rfc-editor.org/info/rfc3329>.

   [RFC3436]  Jungmaier, A., Rescorla, E., and M. Tuexen, "Transport
              Layer Security over Stream Control Transmission Protocol",
              RFC 3436, DOI 10.17487/RFC3436, December 2002,
              <https://www.rfc-editor.org/info/rfc3436>.

   [RFC3470]  Hollenbeck, S., Rose, M., and L. Masinter, "Guidelines for
              the Use of Extensible Markup Language (XML) within IETF
              Protocols", BCP 70, RFC 3470, DOI 10.17487/RFC3470,
              January 2003, <https://www.rfc-editor.org/info/rfc3470>.

   [RFC3501]  Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
              4rev1", RFC 3501, DOI 10.17487/RFC3501, March 2003,
              <https://www.rfc-editor.org/info/rfc3501>.

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552,
              DOI 10.17487/RFC3552, July 2003,
              <https://www.rfc-editor.org/info/rfc3552>.

   [RFC3568]  Barbir, A., Cain, B., Nair, R., and O. Spatscheck, "Known
              Content Network (CN) Request-Routing Mechanisms",
              RFC 3568, DOI 10.17487/RFC3568, July 2003,
              <https://www.rfc-editor.org/info/rfc3568>.

   [RFC3656]  Siemborski, R., "The Mailbox Update (MUPDATE) Distributed
              Mailbox Database Protocol", RFC 3656,
              DOI 10.17487/RFC3656, December 2003,
              <https://www.rfc-editor.org/info/rfc3656>.

   [RFC3749]  Hollenbeck, S., "Transport Layer Security Protocol
              Compression Methods", RFC 3749, DOI 10.17487/RFC3749, May
              2004, <https://www.rfc-editor.org/info/rfc3749>.

   [RFC3767]  Farrell, S., Ed., "Securely Available Credentials
              Protocol", RFC 3767, DOI 10.17487/RFC3767, June 2004,
              <https://www.rfc-editor.org/info/rfc3767>.

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   [RFC3856]  Rosenberg, J., "A Presence Event Package for the Session
              Initiation Protocol (SIP)", RFC 3856,
              DOI 10.17487/RFC3856, August 2004,
              <https://www.rfc-editor.org/info/rfc3856>.

   [RFC3871]  Jones, G., Ed., "Operational Security Requirements for
              Large Internet Service Provider (ISP) IP Network
              Infrastructure", RFC 3871, DOI 10.17487/RFC3871, September
              2004, <https://www.rfc-editor.org/info/rfc3871>.

   [RFC3887]  Hansen, T., "Message Tracking Query Protocol", RFC 3887,
              DOI 10.17487/RFC3887, September 2004,
              <https://www.rfc-editor.org/info/rfc3887>.

   [RFC3903]  Niemi, A., Ed., "Session Initiation Protocol (SIP)
              Extension for Event State Publication", RFC 3903,
              DOI 10.17487/RFC3903, October 2004,
              <https://www.rfc-editor.org/info/rfc3903>.

   [RFC3943]  Friend, R., "Transport Layer Security (TLS) Protocol
              Compression Using Lempel-Ziv-Stac (LZS)", RFC 3943,
              DOI 10.17487/RFC3943, November 2004,
              <https://www.rfc-editor.org/info/rfc3943>.

   [RFC3983]  Newton, A. and M. Sanz, "Using the Internet Registry
              Information Service (IRIS) over the Blocks Extensible
              Exchange Protocol (BEEP)", RFC 3983, DOI 10.17487/RFC3983,
              January 2005, <https://www.rfc-editor.org/info/rfc3983>.

   [RFC4097]  Barnes, M., Ed., "Middlebox Communications (MIDCOM)
              Protocol Evaluation", RFC 4097, DOI 10.17487/RFC4097, June
              2005, <https://www.rfc-editor.org/info/rfc4097>.

   [RFC4111]  Fang, L., Ed., "Security Framework for Provider-
              Provisioned Virtual Private Networks (PPVPNs)", RFC 4111,
              DOI 10.17487/RFC4111, July 2005,
              <https://www.rfc-editor.org/info/rfc4111>.

   [RFC4162]  Lee, H., Yoon, J., and J. Lee, "Addition of SEED Cipher
              Suites to Transport Layer Security (TLS)", RFC 4162,
              DOI 10.17487/RFC4162, August 2005,
              <https://www.rfc-editor.org/info/rfc4162>.

   [RFC4168]  Rosenberg, J., Schulzrinne, H., and G. Camarillo, "The
              Stream Control Transmission Protocol (SCTP) as a Transport
              for the Session Initiation Protocol (SIP)", RFC 4168,
              DOI 10.17487/RFC4168, October 2005,
              <https://www.rfc-editor.org/info/rfc4168>.

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   [RFC4217]  Ford-Hutchinson, P., "Securing FTP with TLS", RFC 4217,
              DOI 10.17487/RFC4217, October 2005,
              <https://www.rfc-editor.org/info/rfc4217>.

   [RFC4235]  Rosenberg, J., Schulzrinne, H., and R. Mahy, Ed., "An
              INVITE-Initiated Dialog Event Package for the Session
              Initiation Protocol (SIP)", RFC 4235,
              DOI 10.17487/RFC4235, November 2005,
              <https://www.rfc-editor.org/info/rfc4235>.

   [RFC4261]  Walker, J. and A. Kulkarni, Ed., "Common Open Policy
              Service (COPS) Over Transport Layer Security (TLS)",
              RFC 4261, DOI 10.17487/RFC4261, December 2005,
              <https://www.rfc-editor.org/info/rfc4261>.

   [RFC4279]  Eronen, P., Ed. and H. Tschofenig, Ed., "Pre-Shared Key
              Ciphersuites for Transport Layer Security (TLS)",
              RFC 4279, DOI 10.17487/RFC4279, December 2005,
              <https://www.rfc-editor.org/info/rfc4279>.

   [RFC4346]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.1", RFC 4346,
              DOI 10.17487/RFC4346, April 2006,
              <https://www.rfc-editor.org/info/rfc4346>.

   [RFC4497]  Elwell, J., Derks, F., Mourot, P., and O. Rousseau,
              "Interworking between the Session Initiation Protocol
              (SIP) and QSIG", BCP 117, RFC 4497, DOI 10.17487/RFC4497,
              May 2006, <https://www.rfc-editor.org/info/rfc4497>.

   [RFC4513]  Harrison, R., Ed., "Lightweight Directory Access Protocol
              (LDAP): Authentication Methods and Security Mechanisms",
              RFC 4513, DOI 10.17487/RFC4513, June 2006,
              <https://www.rfc-editor.org/info/rfc4513>.

   [RFC4531]  Zeilenga, K., "Lightweight Directory Access Protocol
              (LDAP) Turn Operation", RFC 4531, DOI 10.17487/RFC4531,
              June 2006, <https://www.rfc-editor.org/info/rfc4531>.

   [RFC4540]  Stiemerling, M., Quittek, J., and C. Cadar, "NEC's Simple
              Middlebox Configuration (SIMCO) Protocol Version 3.0",
              RFC 4540, DOI 10.17487/RFC4540, May 2006,
              <https://www.rfc-editor.org/info/rfc4540>.

   [RFC4582]  Camarillo, G., Ott, J., and K. Drage, "The Binary Floor
              Control Protocol (BFCP)", RFC 4582, DOI 10.17487/RFC4582,
              November 2006, <https://www.rfc-editor.org/info/rfc4582>.

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   [RFC4616]  Zeilenga, K., Ed., "The PLAIN Simple Authentication and
              Security Layer (SASL) Mechanism", RFC 4616,
              DOI 10.17487/RFC4616, August 2006,
              <https://www.rfc-editor.org/info/rfc4616>.

   [RFC4642]  Murchison, K., Vinocur, J., and C. Newman, "Using
              Transport Layer Security (TLS) with Network News Transfer
              Protocol (NNTP)", RFC 4642, DOI 10.17487/RFC4642, October
              2006, <https://www.rfc-editor.org/info/rfc4642>.

   [RFC4680]  Santesson, S., "TLS Handshake Message for Supplemental
              Data", RFC 4680, DOI 10.17487/RFC4680, October 2006,
              <https://www.rfc-editor.org/info/rfc4680>.

   [RFC4681]  Santesson, S., Medvinsky, A., and J. Ball, "TLS User
              Mapping Extension", RFC 4681, DOI 10.17487/RFC4681,
              October 2006, <https://www.rfc-editor.org/info/rfc4681>.

   [RFC4712]  Siddiqui, A., Romascanu, D., Golovinsky, E., Rahman, M.,
              and Y. Kim, "Transport Mappings for Real-time Application
              Quality-of-Service Monitoring (RAQMON) Protocol Data Unit
              (PDU)", RFC 4712, DOI 10.17487/RFC4712, October 2006,
              <https://www.rfc-editor.org/info/rfc4712>.

   [RFC4732]  Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet
              Denial-of-Service Considerations", RFC 4732,
              DOI 10.17487/RFC4732, December 2006,
              <https://www.rfc-editor.org/info/rfc4732>.

   [RFC4743]  Goddard, T., "Using NETCONF over the Simple Object Access
              Protocol (SOAP)", RFC 4743, DOI 10.17487/RFC4743, December
              2006, <https://www.rfc-editor.org/info/rfc4743>.

   [RFC4744]  Lear, E. and K. Crozier, "Using the NETCONF Protocol over
              the Blocks Extensible Exchange Protocol (BEEP)", RFC 4744,
              DOI 10.17487/RFC4744, December 2006,
              <https://www.rfc-editor.org/info/rfc4744>.

   [RFC4785]  Blumenthal, U. and P. Goel, "Pre-Shared Key (PSK)
              Ciphersuites with NULL Encryption for Transport Layer
              Security (TLS)", RFC 4785, DOI 10.17487/RFC4785, January
              2007, <https://www.rfc-editor.org/info/rfc4785>.

   [RFC4791]  Daboo, C., Desruisseaux, B., and L. Dusseault,
              "Calendaring Extensions to WebDAV (CalDAV)", RFC 4791,
              DOI 10.17487/RFC4791, March 2007,
              <https://www.rfc-editor.org/info/rfc4791>.

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   [RFC4823]  Harding, T. and R. Scott, "FTP Transport for Secure Peer-
              to-Peer Business Data Interchange over the Internet",
              RFC 4823, DOI 10.17487/RFC4823, April 2007,
              <https://www.rfc-editor.org/info/rfc4823>.

   [RFC4851]  Cam-Winget, N., McGrew, D., Salowey, J., and H. Zhou, "The
              Flexible Authentication via Secure Tunneling Extensible
              Authentication Protocol Method (EAP-FAST)", RFC 4851,
              DOI 10.17487/RFC4851, May 2007,
              <https://www.rfc-editor.org/info/rfc4851>.

   [RFC4964]  Allen, A., Ed., Holm, J., and T. Hallin, "The P-Answer-
              State Header Extension to the Session Initiation Protocol
              for the Open Mobile Alliance Push to Talk over Cellular",
              RFC 4964, DOI 10.17487/RFC4964, September 2007,
              <https://www.rfc-editor.org/info/rfc4964>.

   [RFC4975]  Campbell, B., Ed., Mahy, R., Ed., and C. Jennings, Ed.,
              "The Message Session Relay Protocol (MSRP)", RFC 4975,
              DOI 10.17487/RFC4975, September 2007,
              <https://www.rfc-editor.org/info/rfc4975>.

   [RFC4976]  Jennings, C., Mahy, R., and A. Roach, "Relay Extensions
              for the Message Sessions Relay Protocol (MSRP)", RFC 4976,
              DOI 10.17487/RFC4976, September 2007,
              <https://www.rfc-editor.org/info/rfc4976>.

   [RFC4992]  Newton, A., "XML Pipelining with Chunks for the Internet
              Registry Information Service", RFC 4992,
              DOI 10.17487/RFC4992, August 2007,
              <https://www.rfc-editor.org/info/rfc4992>.

   [RFC5018]  Camarillo, G., "Connection Establishment in the Binary
              Floor Control Protocol (BFCP)", RFC 5018,
              DOI 10.17487/RFC5018, September 2007,
              <https://www.rfc-editor.org/info/rfc5018>.

   [RFC5019]  Deacon, A. and R. Hurst, "The Lightweight Online
              Certificate Status Protocol (OCSP) Profile for High-Volume
              Environments", RFC 5019, DOI 10.17487/RFC5019, September
              2007, <https://www.rfc-editor.org/info/rfc5019>.

   [RFC5023]  Gregorio, J., Ed. and B. de hOra, Ed., "The Atom
              Publishing Protocol", RFC 5023, DOI 10.17487/RFC5023,
              October 2007, <https://www.rfc-editor.org/info/rfc5023>.

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   [RFC5024]  Friend, I., "ODETTE File Transfer Protocol 2.0", RFC 5024,
              DOI 10.17487/RFC5024, November 2007,
              <https://www.rfc-editor.org/info/rfc5024>.

   [RFC5049]  Bormann, C., Liu, Z., Price, R., and G. Camarillo, Ed.,
              "Applying Signaling Compression (SigComp) to the Session
              Initiation Protocol (SIP)", RFC 5049,
              DOI 10.17487/RFC5049, December 2007,
              <https://www.rfc-editor.org/info/rfc5049>.

   [RFC5054]  Taylor, D., Wu, T., Mavrogiannopoulos, N., and T. Perrin,
              "Using the Secure Remote Password (SRP) Protocol for TLS
              Authentication", RFC 5054, DOI 10.17487/RFC5054, November
              2007, <https://www.rfc-editor.org/info/rfc5054>.

   [RFC5091]  Boyen, X. and L. Martin, "Identity-Based Cryptography
              Standard (IBCS) #1: Supersingular Curve Implementations of
              the BF and BB1 Cryptosystems", RFC 5091,
              DOI 10.17487/RFC5091, December 2007,
              <https://www.rfc-editor.org/info/rfc5091>.

   [RFC5158]  Huston, G., "6to4 Reverse DNS Delegation Specification",
              RFC 5158, DOI 10.17487/RFC5158, March 2008,
              <https://www.rfc-editor.org/info/rfc5158>.

   [RFC5216]  Simon, D., Aboba, B., and R. Hurst, "The EAP-TLS
              Authentication Protocol", RFC 5216, DOI 10.17487/RFC5216,
              March 2008, <https://www.rfc-editor.org/info/rfc5216>.

   [RFC5238]  Phelan, T., "Datagram Transport Layer Security (DTLS) over
              the Datagram Congestion Control Protocol (DCCP)",
              RFC 5238, DOI 10.17487/RFC5238, May 2008,
              <https://www.rfc-editor.org/info/rfc5238>.

   [RFC5263]  Lonnfors, M., Costa-Requena, J., Leppanen, E., and H.
              Khartabil, "Session Initiation Protocol (SIP) Extension
              for Partial Notification of Presence Information",
              RFC 5263, DOI 10.17487/RFC5263, September 2008,
              <https://www.rfc-editor.org/info/rfc5263>.

   [RFC5281]  Funk, P. and S. Blake-Wilson, "Extensible Authentication
              Protocol Tunneled Transport Layer Security Authenticated
              Protocol Version 0 (EAP-TTLSv0)", RFC 5281,
              DOI 10.17487/RFC5281, August 2008,
              <https://www.rfc-editor.org/info/rfc5281>.

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   [RFC5364]  Garcia-Martin, M. and G. Camarillo, "Extensible Markup
              Language (XML) Format Extension for Representing Copy
              Control Attributes in Resource Lists", RFC 5364,
              DOI 10.17487/RFC5364, October 2008,
              <https://www.rfc-editor.org/info/rfc5364>.

   [RFC5422]  Cam-Winget, N., McGrew, D., Salowey, J., and H. Zhou,
              "Dynamic Provisioning Using Flexible Authentication via
              Secure Tunneling Extensible Authentication Protocol (EAP-
              FAST)", RFC 5422, DOI 10.17487/RFC5422, March 2009,
              <https://www.rfc-editor.org/info/rfc5422>.

   [RFC5469]  Eronen, P., Ed., "DES and IDEA Cipher Suites for Transport
              Layer Security (TLS)", RFC 5469, DOI 10.17487/RFC5469,
              February 2009, <https://www.rfc-editor.org/info/rfc5469>.

   [RFC5734]  Hollenbeck, S., "Extensible Provisioning Protocol (EPP)
              Transport over TCP", STD 69, RFC 5734,
              DOI 10.17487/RFC5734, August 2009,
              <https://www.rfc-editor.org/info/rfc5734>.

   [RFC5878]  Brown, M. and R. Housley, "Transport Layer Security (TLS)
              Authorization Extensions", RFC 5878, DOI 10.17487/RFC5878,
              May 2010, <https://www.rfc-editor.org/info/rfc5878>.

   [RFC5953]  Hardaker, W., "Transport Layer Security (TLS) Transport
              Model for the Simple Network Management Protocol (SNMP)",
              RFC 5953, DOI 10.17487/RFC5953, August 2010,
              <https://www.rfc-editor.org/info/rfc5953>.

   [RFC6042]  Keromytis, A., "Transport Layer Security (TLS)
              Authorization Using KeyNote", RFC 6042,
              DOI 10.17487/RFC6042, October 2010,
              <https://www.rfc-editor.org/info/rfc6042>.

   [RFC6176]  Turner, S. and T. Polk, "Prohibiting Secure Sockets Layer
              (SSL) Version 2.0", RFC 6176, DOI 10.17487/RFC6176, March
              2011, <https://www.rfc-editor.org/info/rfc6176>.

   [RFC6353]  Hardaker, W., "Transport Layer Security (TLS) Transport
              Model for the Simple Network Management Protocol (SNMP)",
              STD 78, RFC 6353, DOI 10.17487/RFC6353, July 2011,
              <https://www.rfc-editor.org/info/rfc6353>.

   [RFC6367]  Kanno, S. and M. Kanda, "Addition of the Camellia Cipher
              Suites to Transport Layer Security (TLS)", RFC 6367,
              DOI 10.17487/RFC6367, September 2011,
              <https://www.rfc-editor.org/info/rfc6367>.

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   [RFC6739]  Schulzrinne, H. and H. Tschofenig, "Synchronizing Service
              Boundaries and <mapping> Elements Based on the Location-
              to-Service Translation (LoST) Protocol", RFC 6739,
              DOI 10.17487/RFC6739, October 2012,
              <https://www.rfc-editor.org/info/rfc6739>.

   [RFC6749]  Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
              RFC 6749, DOI 10.17487/RFC6749, October 2012,
              <https://www.rfc-editor.org/info/rfc6749>.

   [RFC6750]  Jones, M. and D. Hardt, "The OAuth 2.0 Authorization
              Framework: Bearer Token Usage", RFC 6750,
              DOI 10.17487/RFC6750, October 2012,
              <https://www.rfc-editor.org/info/rfc6750>.

   [RFC7030]  Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
              "Enrollment over Secure Transport", RFC 7030,
              DOI 10.17487/RFC7030, October 2013,
              <https://www.rfc-editor.org/info/rfc7030>.

   [RFC7465]  Popov, A., "Prohibiting RC4 Cipher Suites", RFC 7465,
              DOI 10.17487/RFC7465, February 2015,
              <https://www.rfc-editor.org/info/rfc7465>.

   [RFC7507]  Moeller, B. and A. Langley, "TLS Fallback Signaling Cipher
              Suite Value (SCSV) for Preventing Protocol Downgrade
              Attacks", RFC 7507, DOI 10.17487/RFC7507, April 2015,
              <https://www.rfc-editor.org/info/rfc7507>.

   [RFC7525]  Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
              2015, <https://www.rfc-editor.org/info/rfc7525>.

   [RFC7562]  Thakore, D., "Transport Layer Security (TLS) Authorization
              Using Digital Transmission Content Protection (DTCP)
              Certificates", RFC 7562, DOI 10.17487/RFC7562, July 2015,
              <https://www.rfc-editor.org/info/rfc7562>.

   [RFC7568]  Barnes, R., Thomson, M., Pironti, A., and A. Langley,
              "Deprecating Secure Sockets Layer Version 3.0", RFC 7568,
              DOI 10.17487/RFC7568, June 2015,
              <https://www.rfc-editor.org/info/rfc7568>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

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   [RFC8422]  Nir, Y., Josefsson, S., and M. Pegourie-Gonnard, "Elliptic
              Curve Cryptography (ECC) Cipher Suites for Transport Layer
              Security (TLS) Versions 1.2 and Earlier", RFC 8422,
              DOI 10.17487/RFC8422, August 2018,
              <https://www.rfc-editor.org/info/rfc8422>.

11.2.  Informative References

   [Bhargavan2016]
              Bhargavan, K. and G. Leuren, "Transcript Collision
              Attacks: Breaking Authentication in TLS, IKE, and SSH
              https://www.mitls.org/downloads/transcript-
              collisions.pdf", 2016.

   [NIST800-52r2]
              National Institute of Standards and Technology, "NIST
              SP800-52r2
              https://nvlpubs.nist.gov/nistpubs/SpecialPublications/
              NIST.SP.800-52r2.pdf", August 2019.

   [RFC3316]  Arkko, J., Kuijpers, G., Soliman, H., Loughney, J., and J.
              Wiljakka, "Internet Protocol Version 6 (IPv6) for Some
              Second and Third Generation Cellular Hosts", RFC 3316,
              DOI 10.17487/RFC3316, April 2003,
              <https://www.rfc-editor.org/info/rfc3316>.

   [RFC3489]  Rosenberg, J., Weinberger, J., Huitema, C., and R. Mahy,
              "STUN - Simple Traversal of User Datagram Protocol (UDP)
              Through Network Address Translators (NATs)", RFC 3489,
              DOI 10.17487/RFC3489, March 2003,
              <https://www.rfc-editor.org/info/rfc3489>.

   [RFC3546]  Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J.,
              and T. Wright, "Transport Layer Security (TLS)
              Extensions", RFC 3546, DOI 10.17487/RFC3546, June 2003,
              <https://www.rfc-editor.org/info/rfc3546>.

   [RFC3588]  Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
              Arkko, "Diameter Base Protocol", RFC 3588,
              DOI 10.17487/RFC3588, September 2003,
              <https://www.rfc-editor.org/info/rfc3588>.

   [RFC3734]  Hollenbeck, S., "Extensible Provisioning Protocol (EPP)
              Transport Over TCP", RFC 3734, DOI 10.17487/RFC3734, March
              2004, <https://www.rfc-editor.org/info/rfc3734>.

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   [RFC3920]  Saint-Andre, P., Ed., "Extensible Messaging and Presence
              Protocol (XMPP): Core", RFC 3920, DOI 10.17487/RFC3920,
              October 2004, <https://www.rfc-editor.org/info/rfc3920>.

   [RFC4132]  Moriai, S., Kato, A., and M. Kanda, "Addition of Camellia
              Cipher Suites to Transport Layer Security (TLS)",
              RFC 4132, DOI 10.17487/RFC4132, July 2005,
              <https://www.rfc-editor.org/info/rfc4132>.

   [RFC4244]  Barnes, M., Ed., "An Extension to the Session Initiation
              Protocol (SIP) for Request History Information", RFC 4244,
              DOI 10.17487/RFC4244, November 2005,
              <https://www.rfc-editor.org/info/rfc4244>.

   [RFC4347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security", RFC 4347, DOI 10.17487/RFC4347, April 2006,
              <https://www.rfc-editor.org/info/rfc4347>.

   [RFC4366]  Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J.,
              and T. Wright, "Transport Layer Security (TLS)
              Extensions", RFC 4366, DOI 10.17487/RFC4366, April 2006,
              <https://www.rfc-editor.org/info/rfc4366>.

   [RFC4492]  Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B.
              Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites
              for Transport Layer Security (TLS)", RFC 4492,
              DOI 10.17487/RFC4492, May 2006,
              <https://www.rfc-editor.org/info/rfc4492>.

   [RFC4507]  Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,
              "Transport Layer Security (TLS) Session Resumption without
              Server-Side State", RFC 4507, DOI 10.17487/RFC4507, May
              2006, <https://www.rfc-editor.org/info/rfc4507>.

   [RFC4572]  Lennox, J., "Connection-Oriented Media Transport over the
              Transport Layer Security (TLS) Protocol in the Session
              Description Protocol (SDP)", RFC 4572,
              DOI 10.17487/RFC4572, July 2006,
              <https://www.rfc-editor.org/info/rfc4572>.

   [RFC4934]  Hollenbeck, S., "Extensible Provisioning Protocol (EPP)
              Transport Over TCP", RFC 4934, DOI 10.17487/RFC4934, May
              2007, <https://www.rfc-editor.org/info/rfc4934>.

   [RFC5077]  Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,
              "Transport Layer Security (TLS) Session Resumption without
              Server-Side State", RFC 5077, DOI 10.17487/RFC5077,
              January 2008, <https://www.rfc-editor.org/info/rfc5077>.

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   [RFC5081]  Mavrogiannopoulos, N., "Using OpenPGP Keys for Transport
              Layer Security (TLS) Authentication", RFC 5081,
              DOI 10.17487/RFC5081, November 2007,
              <https://www.rfc-editor.org/info/rfc5081>.

   [RFC5101]  Claise, B., Ed., "Specification of the IP Flow Information
              Export (IPFIX) Protocol for the Exchange of IP Traffic
              Flow Information", RFC 5101, DOI 10.17487/RFC5101, January
              2008, <https://www.rfc-editor.org/info/rfc5101>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/info/rfc5246>.

   [RFC5415]  Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley,
              Ed., "Control And Provisioning of Wireless Access Points
              (CAPWAP) Protocol Specification", RFC 5415,
              DOI 10.17487/RFC5415, March 2009,
              <https://www.rfc-editor.org/info/rfc5415>.

   [RFC5456]  Spencer, M., Capouch, B., Guy, E., Ed., Miller, F., and K.
              Shumard, "IAX: Inter-Asterisk eXchange Version 2",
              RFC 5456, DOI 10.17487/RFC5456, February 2010,
              <https://www.rfc-editor.org/info/rfc5456>.

   [RFC6012]  Salowey, J., Petch, T., Gerhards, R., and H. Feng,
              "Datagram Transport Layer Security (DTLS) Transport
              Mapping for Syslog", RFC 6012, DOI 10.17487/RFC6012,
              October 2010, <https://www.rfc-editor.org/info/rfc6012>.

   [RFC6083]  Tuexen, M., Seggelmann, R., and E. Rescorla, "Datagram
              Transport Layer Security (DTLS) for Stream Control
              Transmission Protocol (SCTP)", RFC 6083,
              DOI 10.17487/RFC6083, January 2011,
              <https://www.rfc-editor.org/info/rfc6083>.

   [RFC6084]  Fu, X., Dickmann, C., and J. Crowcroft, "General Internet
              Signaling Transport (GIST) over Stream Control
              Transmission Protocol (SCTP) and Datagram Transport Layer
              Security (DTLS)", RFC 6084, DOI 10.17487/RFC6084, January
              2011, <https://www.rfc-editor.org/info/rfc6084>.

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
              January 2012, <https://www.rfc-editor.org/info/rfc6347>.

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   [RFC6460]  Salter, M. and R. Housley, "Suite B Profile for Transport
              Layer Security (TLS)", RFC 6460, DOI 10.17487/RFC6460,
              January 2012, <https://www.rfc-editor.org/info/rfc6460>.

   [RFC6614]  Winter, S., McCauley, M., Venaas, S., and K. Wierenga,
              "Transport Layer Security (TLS) Encryption for RADIUS",
              RFC 6614, DOI 10.17487/RFC6614, May 2012,
              <https://www.rfc-editor.org/info/rfc6614>.

   [RFC7457]  Sheffer, Y., Holz, R., and P. Saint-Andre, "Summarizing
              Known Attacks on Transport Layer Security (TLS) and
              Datagram TLS (DTLS)", RFC 7457, DOI 10.17487/RFC7457,
              February 2015, <https://www.rfc-editor.org/info/rfc7457>.

   [RFC8143]  Elie, J., "Using Transport Layer Security (TLS) with
              Network News Transfer Protocol (NNTP)", RFC 8143,
              DOI 10.17487/RFC8143, April 2017,
              <https://www.rfc-editor.org/info/rfc8143>.

   [RFC8261]  Tuexen, M., Stewart, R., Jesup, R., and S. Loreto,
              "Datagram Transport Layer Security (DTLS) Encapsulation of
              SCTP Packets", RFC 8261, DOI 10.17487/RFC8261, November
              2017, <https://www.rfc-editor.org/info/rfc8261>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [RFC8447]  Salowey, J. and S. Turner, "IANA Registry Updates for TLS
              and DTLS", RFC 8447, DOI 10.17487/RFC8447, August 2018,
              <https://www.rfc-editor.org/info/rfc8447>.

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Appendix A.  Change Log

   [[RFC editor: please remove this before publication.]]

   From draft-ietf-tls-oldversions-deprecate-11 to draft-ietf-tls-
   oldversions-deprecate-12 (IESG review):

   o  Minor edits from IESG review comments.

   From draft-ietf-tls-oldversions-deprecate-10 to draft-ietf-tls-
   oldversions-deprecate-11:

   o  RFC 5953 was mentioned in the wrong para of section 1.1 - it has
      been obsoleted already.

   From draft-ietf-tls-oldversions-deprecate-09 to draft-ietf-tls-
   oldversions-deprecate-10:

   o  We missed adding change logs for a few versions, but since -09 was
      the one that underwent IETF last call, and there was some
      discussion, we figured it'd be good to mention substantive changes
      here.
   o  Added Ben's suggested text for "operational considerations"
      following extensive last call discussion.
   o  Re-checked the references to RFC 4347 after Tom Petch noticed we
      missed a couple.  Added RFCs 5953 and 6353 to the list here.  All
      others were in already.
   o  Fixed various typos and ack'd those who engaged a bit in the IETF
      LC discussion.  (If we missed you and you want to be added, or if
      you'd rather not be mentioned, just ping the authors.)

   From draft-ietf-tls-oldversions-deprecate-05 to draft-ietf-tls-
   oldversions-deprecate-06:

   o  Fixed "yaleman" ack.
   o  Added RFC6614 to UPDATEs list.
   o  per preliminary AD review:

      *  Remove references from abstract
      *  s/primary technical reasons/technical reasons/
      *  Add rfc7030 to 1.1
      *  verified that all the RFCs in the (massive:-) Updates meta-data
         are mentioned in section 1.1 (I think appropriately;-)

   From draft-ietf-tls-oldversions-deprecate-04 to draft-ietf-tls-
   oldversions-deprecate-05:

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   o  Removed references to goverment related deprecation statements:
      US, Canada, and Germany.  NIST documentation rationale remains as
      a reference describing the relevent RFCs and justification.

   From draft-ietf-tls-oldversions-deprecate-02 to draft-ietf-tls-
   oldversions-deprecate-03:

   o  Added 8261 to updates list based on IETF-104 meeting.

   From draft-ietf-tls-oldversions-deprecate-01 to draft-ietf-tls-
   oldversions-deprecate-02:

   o  Correction: 2nd list of referenced RFCs in Section 1.1 aren't
      informatively refering to tls1.0/1.1
   o  Remove RFC7255 from updates list - datatracker has bad data
      (spotted by Robert Sparks)
   o  Added point about RFCs 8143 and 4642
   o  Added UPDATEs for RFCs that refer to 4347 and aren't OBSOLETEd
   o  Added note about RFC8261 to see what WG want.

   From draft-ietf-tls-oldversions-deprecate-00 to draft-ietf-tls-
   oldversions-deprecate-01:

   o  PRs with typos and similar: so far just #1
   o  PR#2 noting msft browser announced deprecation (but this was OBE
      as per...)
   o  Implemented actions as per IETF-103 meeting:

      *  Details about which RFC's, BCP's are affected were generated
         using a script in the git repo: https://github.com/tlswg/
         oldversions-deprecate/blob/master/nonobsnorms.sh
      *  Removed the 'measurements' part
      *  Removed SHA-1 deprecation (section 8 of -00)

   From draft-moriarty-tls-oldversions-diediedie-01 to draft-ietf-tls-
   oldversions-deprecate-00:

   o  I-Ds became RFCs 8446/8447 (old-repo PR#4, for TLSv1.3)
   o  Accepted old-repo PR#5 fixing typos

   From draft-moriarty-tls-oldversions-diediedie-00 to draft-moriarty-
   tls-oldversions-diediedie-01:

   o  Added stats sent to list so far
   o  PR's #2,3
   o  a few more references
   o  added section on email

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Authors' Addresses

   Kathleen Moriarty
   Dell EMC
   176 South Street
   Hopkinton
   United States

   EMail: Kathleen.Moriarty.ietf@gmail.com

   Stephen Farrell
   Trinity College Dublin
   Dublin  2
   Ireland

   Phone: +353-1-896-2354
   EMail: stephen.farrell@cs.tcd.ie

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