Network Working Group J. Preuss Mattsson
Internet-Draft G. Selander
Updates: draft-ietf-cose-x509 (if Ericsson AB
approved) S. Raza
Intended status: Standards Track J. Hoeglund
Expires: September 10, 2020 RISE AB
M. Furuhed
Nexus Group
March 09, 2020
CBOR Object Signing and Encryption (COSE): Headers for Carrying CBOR
Compressed Certificates
draft-mattsson-cose-cbor-cert-compress-00
Abstract
Certificate chains often take up the majority of the bytes
transmitted in COSE message that carry certificates. Large messages
can cause problems, particularly in constrained IoT environments.
RFC 7925 defines a 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 COSE.
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
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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
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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
[I-D.ietf-cose-x509] provides attributes that refer to or contain
X.509 certificates. X.509 certificates often take up the majority of
the bytes transmitted in COSE messages that carry certificates.
Large messages negatively affect latency, but can also result in that
the security protocol cannot be completed [I-D.ietf-emu-eaptlscert].
Large messages 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 well also
for COSE and other protocols. For such RFC 7925 profiled IoT
certificates, general purpose compression algorithms can in many
cases only provide negliable or no compression 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%.
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This document specifies the CBOR certificate compression algorithm
[I-D.raza-ace-cbor-certificates] for use with COSE.
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 COSE.
The CBOR Certificate compression algorithm takes as input an 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. See Appendix A of [I-D.raza-ace-cbor-certificates] for
details.
+------------------+--------------+------------+--------------------+
| | RFC 7925 | zlib | CBOR Certificate |
+------------------+---------------------------+--------------------+
| Certificate Size | 314 | 295 | 136 |
+------------------+--------------+------------+--------------------+
The header attributes defined in this document are:
CBORchain: This header attribute contains an ordered array of
certicates similar to x5chain [I-D.ietf-cose-x509]. The
difference being that all the included certificates are CBOR
certificates [I-D.raza-ace-cbor-certificates] instead of DER
encoded X.509 certificates.
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+-----------+-------+----------------+---------------------+
| Name | Label | Value Type | Description |
+===========+=======+================+=====================+
| CBORchain | TBD1 | COSE_CBOR_Cert | An ordered chain of |
| | | | CBOR certificates |
+-----------+-------+----------------+---------------------+
Below is an equivalent CDDL [RFC8610] description of the text above.
COSE_CBOR_Cert = bstr / [ 2*certs: bstr ]
4. Security Considerations
The security considerations in [I-D.ietf-cose-x509] and
[I-D.raza-ace-cbor-certificates] apply.
5. IANA Considerations
This document registers the COSE Header items in Table 1 in the "COSE
Header Parameters" registry under the "CBOR Object Signing and
Encryption (COSE)" heading. For each item, the 'Reference' field
points to 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-cose-x509]
Schaad, J., "CBOR Object Signing and Encryption (COSE):
Headers for carrying and referencing X.509 certificates",
draft-ietf-cose-x509-05 (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>.
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>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/info/rfc8610>.
Acknowledgments
The authors want to thank TBD for their valuable comments and
feedback.
Authors' Addresses
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John Preuss Mattsson
Ericsson AB
Email: john.mattsson@ericsson.com
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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