MOCHA Personal Address Book

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Table of Contents

1. Introduction

MOCHA users need to maintain a personal directory of contacts — mapping user identities (e.g., alice@provider.example) to display names and other metadata they trust. This address book must synchronize across all devices belonging to the same user without requiring a centralized contacts server.¶

This document specifies:¶

• The MOQT namespace and track structure for address book data¶

• The contact card format (based on jCard [RFC7095])¶

• The synchronization model across a user's devices¶

• Group and object organization for efficient retrieval¶

2. Conventions and Definitions

See BCP 14 [RFC2119] [RFC8174].¶

This document uses terminology defined in [MOCHA-ARCH], including Provider, Organization, UserID, and Device. HDevID is defined in [MOCHA-IDENTITY].¶

The following additional terms are used:¶

Personal Address Book (PAB):

A per-user collection of contact cards synchronized across all of the user's devices via MOQT.¶

Contact Card:

A single entry in the address book, encoded as a jCard [RFC7095] object. Each card maps an identity to a human-readable name and optional metadata.¶

3. Namespace and Track Structure

  ("mocha_v1", <Provider>, <OrgID>, "pab", <UserID>)

  Track Name: ("msg", <HDevID>)

  Namespace: ("mocha_v1", "example.com", "acme", "pab", "alice")
  Track:     ("msg", "device-a3f2")

4. Group and Object Organization

  Group ID = (year - 2024) * 12 + (month - 1)

  Example: June 2026 = (2026 - 2024) * 12 + (6 - 1) = 29

  Namespace: ("mocha_v1", "example.com", "acme", "pab", "alice")
  Track:     ("msg", "device-a3f2")
  Group:     29 (June 2026)
  Object:    0, 1, 2, ... (sequential operations)

5. Contact Card Format

{
  "op": "add" | "update" | "delete",
  "id": "<contact identity>",
  "timestamp": <unix timestamp>,
  "card": <jCard object (for add/update)>
}

{
  "op": "add",
  "id": "bob@example.com",
  "timestamp": 1751000000,
  "card": ["vcard", [
    ["version", {}, "text", "4.0"],
    ["fn", {}, "text", "Bob Smith"],
    ["email", {}, "text", "bob@example.com"]
  ]]
}

{
  "op": "delete",
  "id": "bob@example.com",
  "timestamp": 1751100000
}

6. Synchronization Model

  SUBSCRIBE_NAMESPACE ("mocha_v1", <Provider>, <OrgID>,
                       "pab", <UserID>)

7. Authorization

Access to a user's PAB namespace is restricted to that user's own devices. The Token Service issues C4M tokens (or Privacy Pass tokens) scoped to the user's PAB namespace:¶

  publish:   ["mocha_v1/<provider>/<org>/pab/<user_id>/msg/<own-device>"]
  subscribe: ["mocha_v1/<provider>/<org>/pab/<user_id>/*"]

Each device can only publish to its own track but can subscribe to all tracks within the user's PAB namespace.¶

8. Security Considerations

TODO¶

9. IANA Considerations

This document makes no requests of IANA.¶

10. Normative References

[MOCHA-ARCH]

"*** BROKEN REFERENCE ***".

[MOCHA-IDENTITY]

Jennings, C. F. and S. Nandakumar, "MOCHA Identity: Authentication, Authorization, and Federation", Work in Progress, Internet-Draft, draft-jennings-moq-mocha-identity-00, 6 July 2026, <https://datatracker.ietf.org/doc/html/draft-jennings-moq-mocha-identity-00>.

[MoQTransport]

Nandakumar, S., Vasiliev, V., Swett, I., and A. Frindell, "Media over QUIC Transport", Work in Progress, Internet-Draft, draft-ietf-moq-transport-18, 12 May 2026, <https://datatracker.ietf.org/doc/html/draft-ietf-moq-transport-18>.

[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/rfc/rfc2119>.

[RFC7095]

Kewisch, P., "jCard: The JSON Format for vCard", RFC 7095, DOI 10.17487/RFC7095, January 2014, <https://www.rfc-editor.org/rfc/rfc7095>.

[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/rfc/rfc8174>.

[RFC8259]

Bray, T., Ed., "The JavaScript Object Notation (JSON) Data Interchange Format", STD 90, RFC 8259, DOI 10.17487/RFC8259, December 2017, <https://www.rfc-editor.org/rfc/rfc8259>.

Authors' Addresses