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
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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
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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
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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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