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Network Working Group                                 J. Preuss Mattsson
Internet-Draft                                               G. Selander
Updates: draft-ietf-tls-certificate-                         Ericsson AB
         compression (if approved)                               S. Raza
Intended status: Standards Track                             J. Hoeglund
Expires: September 10, 2020                                      RISE AB
                                                              M. Furuhed
                                                             Nexus Group
                                                          March 09, 2020


       CBOR Certificate Algorithm for TLS Certificate Compression
                draft-mattsson-tls-cbor-cert-compress-00

Abstract

   Certificate chains often take up the majority of the bytes
   transmitted in TLS handshakes.  Large handshakes can cause problems,
   particularly in constrained IoT environments.  RFC 7925 defines a TLS
   certificate profile for constrained IoT.  General purpose compression
   algorithms can in many cases not compress RFC 7925 profiled
   certificates at all.  By using the fact that the certificates are
   profiled, the CBOR certificate compression algorithms can in many
   cases compress RFC 7925 profiled certificates with over 50%. This
   document specifies the CBOR certificate compression algorithm for use
   with TLS Certificate Compression in TLS 1.3 and DTLS 1.3.

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 September 10, 2020.








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Copyright Notice

   Copyright (c) 2020 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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . .   3
   3.  CBOR Certificate Compression Algorithm  . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   As stated in [I-D.ietf-tls-certificate-compression], certificate
   chains often take up the majority of the bytes transmitted in TLS
   handshakes.  Large handshakes negatively affect latency, but can also
   result in that the handshake cannot be completed
   [I-D.ietf-emu-eaptlscert].  To reduce handshake sizes,
   [I-D.ietf-tls-certificate-compression] specifies a mechanism for
   lossless compression of certificate chains in TLS 1.3 and defines
   three general purpose compression algorithms.

   Large handshakes is particularly a problem for constrained IoT
   environments [RFC7228] [I-D.ietf-lake-reqs].  [RFC7925] defines a
   X.509 certificate profile for constrained IoT.  The certificate
   profile in [RFC7925] is defined for TLS/DTLS 1.2 but works also for
   TLS 1.3 [RFC8446] and DTLS 1.3 [I-D.ietf-tls-dtls13].  For such
   profiled IoT certificates, general purpose compression algorithms
   such as zlib are however far from optimal and the general purpose
   compression algorithms defined in
   [I-D.ietf-tls-certificate-compression] can in many cases not compress



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   RFC 7925 profiled certificates at all.
   [I-D.raza-ace-cbor-certificates] therefore defines a CBOR [RFC7049]
   compression algorithm for RFC 7925 profiled certificates.  The
   algorithm works for all RFC 7925 profiled certificates and provide
   significant reduction in size, in many cases over 50%.

   This document specifies the CBOR certificate compression algorithm
   [I-D.raza-ace-cbor-certificates] for use with TLS Certificate
   Compression [I-D.ietf-tls-certificate-compression].  TLS Certificate
   Compression can be used in TLS 1.3 [RFC8446] and DTLS 1.3
   [I-D.ietf-tls-dtls13].

2.  Notational Conventions

   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.

3.  CBOR Certificate Compression Algorithm

   This document specifies the CBOR certificate compression algorithm
   specified in Section 3 of [I-D.raza-ace-cbor-certificates] for use
   with TLS Certificate Compression
   [I-D.ietf-tls-certificate-compression].  TLS Certificate Compression
   can be used in TLS 1.3 [RFC8446] and DTLS 1.3 [I-D.ietf-tls-dtls13].

   The CBOR Certificate compression algorithm takes as input a RFC 7925
   profiled X.509 certificate.  The output of the CBOR compression
   algorithm is a CBOR Sequence [I-D.ietf-cbor-sequence], i.e. a
   sequence of concatenated CBOR encoded CBOR data items [RFC7049].
   Compressed certificates can be analysed with any CBOR decoder and be
   validated against the CDDL specification defined in Section 3 of
   [I-D.raza-ace-cbor-certificates].

   The algorithm works for all RFC 7925 profiled certificates and
   provide significant reduction in size, in many cases over 50%. An
   example compression of a RFC 7925 profiled certificate is given
   below.

   +------------------+--------------+------------+--------------------+
   |                  |   RFC 7925   |    zlib    |  CBOR Certificate  |
   +------------------+---------------------------+--------------------+
   | Certificate Size |     314      |     295    |         136        |
   +------------------+--------------+------------+--------------------+





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4.  Security Considerations

   The security considerations in [I-D.ietf-tls-certificate-compression]
   and [I-D.raza-ace-cbor-certificates] apply.

5.  IANA Considerations

   This document registers the following entry in the "Certificate
   Compression Algorithm IDs" registry under the "Transport Layer
   Security (TLS) Extensions" heading.

   +------------------+------------------------------+-----------------+
   | Algorithm Number | Description                  | Reference       |
   +------------------+------------------------------+-----------------+
   | TBD              | CBOR Certificate             | [this document] |
   +------------------+------------------------------+-----------------+

6.  References

6.1.  Normative References

   [I-D.ietf-cbor-sequence]
              Bormann, C., "Concise Binary Object Representation (CBOR)
              Sequences", draft-ietf-cbor-sequence-02 (work in
              progress), September 2019.

   [I-D.ietf-tls-certificate-compression]
              Ghedini, A. and V. Vasiliev, "TLS Certificate
              Compression", draft-ietf-tls-certificate-compression-10
              (work in progress), January 2020.

   [I-D.ietf-tls-dtls13]
              Rescorla, E., Tschofenig, H., and N. Modadugu, "The
              Datagram Transport Layer Security (DTLS) Protocol Version
              1.3", draft-ietf-tls-dtls13-34 (work in progress),
              November 2019.

   [I-D.raza-ace-cbor-certificates]
              Raza, S., Hoglund, J., Selander, G., Mattsson, J., and M.
              Furuhed, "CBOR Profile of X.509 Certificates", draft-raza-
              ace-cbor-certificates-03 (work in progress), December
              2019.

   [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>.




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   [RFC7049]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
              October 2013, <https://www.rfc-editor.org/info/rfc7049>.

   [RFC7925]  Tschofenig, H., Ed. and T. Fossati, "Transport Layer
              Security (TLS) / Datagram Transport Layer Security (DTLS)
              Profiles for the Internet of Things", RFC 7925,
              DOI 10.17487/RFC7925, July 2016,
              <https://www.rfc-editor.org/info/rfc7925>.

   [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>.

   [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>.

6.2.  Informative References

   [I-D.ietf-emu-eaptlscert]
              Sethi, M., Mattsson, J., and S. Turner, "Handling Large
              Certificates and Long Certificate Chains in TLS-based EAP
              Methods", draft-ietf-emu-eaptlscert-01 (work in progress),
              March 2020.

   [I-D.ietf-lake-reqs]
              Vucinic, M., Selander, G., Mattsson, J., and D. Garcia-
              Carillo, "Requirements for a Lightweight AKE for OSCORE",
              draft-ietf-lake-reqs-01 (work in progress), February 2020.

   [RFC7228]  Bormann, C., Ersue, M., and A. Keranen, "Terminology for
              Constrained-Node Networks", RFC 7228,
              DOI 10.17487/RFC7228, May 2014,
              <https://www.rfc-editor.org/info/rfc7228>.

Acknowledgments

   The authors want to thank TBD for their valuable comments and
   feedback.

Authors' Addresses

   John Preuss Mattsson
   Ericsson AB

   Email: john.mattsson@ericsson.com




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   Goeran Selander
   Ericsson AB

   Email: goran.selander@ericsson.com


   Shahid Raza
   RISE AB

   Email: shahid.raza@ri.se


   Joel Hoeglund
   RISE AB

   Email: joel.hoglund@ri.se


   Martin Furuhed
   Nexus Group

   Email: martin.furuhed@nexusgroup.com





























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