Concise Binary Object Representation (CBOR) Tags for Date
draft-jones-cbor-date-tag-01

Abstract

The Concise Binary Object Representation (CBOR, RFC 7049) is a data format whose design goals include the possibility of extremely small code size, fairly small message size, and extensibility without the need for version negotiation.

In CBOR, one point of extensibility is the definition of CBOR tags. RFC 7049 defines two tags for time: CBOR tag 0 (RFC 3339 date/time string) and tag 1 (Posix "seconds since the epoch"). Since then, additional requirements have become known. This specification defines a CBOR tag for an RFC 3339 date text string, for applications needing a textual date representation without a time. It also defines a CBOR tag for days since the Posix epoch, for applicaitons needing a numeric date representation without a time. It is intended as the reference document for the IANA registration of the CBOR tags defined.

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This Internet-Draft will expire on October 23, 2020.

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Table of Contents

• 1. Introduction
• 1.1. Requirements Notation and Conventions
• 2. IANA Considerations
• 2.1. Concise Binary Object Representation (CBOR) Tags Registrations
• 3. Security Considerations
• 4. References
• 4.1. Normative References
• 4.2. Informative References
• Acknowledgements
• Document History
• Authors' Addresses

1. Introduction

The Concise Binary Object Representation (CBOR) [RFC7049] provides for the interchange of structured data without a requirement for a pre-agreed schema. RFC 7049 defines a basic set of data types, as well as a tagging mechanism that enables extending the set of data types supported via an IANA registry.

This specification defines a CBOR tag for a text string representing a date but not a time. The tagged text string is represented as specified by the RFC 3339 [RFC3339] full-date production.

This specification also defines a CBOR tag for an integer representing a date but not a time. The tagged integer is a positive or negative value indicating the number of days since the IEEE Std 1003.1, 2013 Edition epoch date 1970-01-01.

1.1. Requirements Notation and 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.

2. IANA Considerations

2.1. Concise Binary Object Representation (CBOR) Tags Registrations

This section registers the following values in the IANA "Concise Binary Object Representation (CBOR) Tags" registry [IANA.cbor-tags].

• Tag: 1004 (value requested)
• Data Item: UTF-8 text string
• Semantics: RFC 3339 full-date string
• Reference: [[ this specification ]]

• Tag: 100 (ASCII 'd') (value requested)
• Data Item: Positive or negative integer
• Semantics: Number of days since the epoch date 1970-01-01
• Reference: [[ this specification ]]

3. Security Considerations

The security considerations of RFC 7049 apply; the tags introduced here are not expected to raise security considerations beyond those.

A date, of course, has significant security considerations; these include the exploitation of ambiguities where the date is security relevant or where the date is used in access control decisions.

4. References

4.1. Normative References

4.2. Informative References

Acknowledgements

Thanks to Carsten Bormann for supporting creation of this specification. Parts of the explanatory text in this specification come from draft-bormann-cbor-time-tag-02.

Document History

[[ to be removed by the RFC Editor before publication as an RFC ]]

-01

• Added tag for numeric date values relative to the Posix Epoch that was proposed by Jörg Richter.

-00

• Initial version.

Authors' Addresses