The Messaging Layer Security (MLS) Architecture
draft-ietf-mls-architecture-05
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2020-07-26
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draft-omara-mls-architecture
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IETF
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Katriel Cohn-Gordon <me@katriel.co.uk>, Cas Cremers <cas.cremers@cs.ox.ac.uk>, Thyla van der Merwe< thyla.van.der@merwe.tech>, Jon Millican <jmillican@fb.com>, Raphael Robert <raphael@wire.com>
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Network Working Group E. Omara
Internet-Draft Google
Intended status: Informational B. Beurdouche
Expires: 27 January 2021 INRIA
E. Rescorla
Mozilla
S. Inguva
Twitter
A. Kwon
MIT
A. Duric
Wire
26 July 2020
The Messaging Layer Security (MLS) Architecture
draft-ietf-mls-architecture-05
Abstract
This document describes the reference architecture, functional and
security requirements for the Messaging Layer Security (MLS)
protocol. MLS provides a security layer for group messaging
applications, where the number of clients ranges from two to many.
It is meant to protect against eavesdropping, tampering, and message
forgery.
Discussion Venues
This note is to be removed before publishing as an RFC.
Source for this draft and an issue tracker can be found at
https://github.com/mlswg/mls-architecture.
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."
Omara, et al. Expires 27 January 2021 [Page 1]
Internet-Draft MLS Architecture July 2020
This Internet-Draft will expire on 27 January 2021.
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 . . . . . . . . . . . . . . . . . . . . . . . . 3
2. General Setting . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Group, Members and Clients . . . . . . . . . . . . . . . 6
2.2. Authentication Service . . . . . . . . . . . . . . . . . 6
2.3. Delivery Service . . . . . . . . . . . . . . . . . . . . 7
2.3.1. Key Storage . . . . . . . . . . . . . . . . . . . . . 8
2.3.2. Key Retrieval . . . . . . . . . . . . . . . . . . . . 8
2.3.3. Delivery of messages and attachments . . . . . . . . 9
2.3.4. Membership knowledge . . . . . . . . . . . . . . . . 10
2.3.5. Membership and offline members . . . . . . . . . . . 10
3. System Requirements . . . . . . . . . . . . . . . . . . . . . 10
3.1. Functional Requirements . . . . . . . . . . . . . . . . . 10
3.1.1. Asynchronous Usage . . . . . . . . . . . . . . . . . 11
3.1.2. Recovery After State Loss . . . . . . . . . . . . . . 11
3.1.3. Support for Multiple Devices . . . . . . . . . . . . 11
3.1.4. Extensibility / Pluggability . . . . . . . . . . . . 11
3.1.5. Privacy . . . . . . . . . . . . . . . . . . . . . . . 12
3.1.6. Federation . . . . . . . . . . . . . . . . . . . . . 12
3.1.7. Compatibility with future versions of MLS . . . . . . 12
3.2. Security Requirements . . . . . . . . . . . . . . . . . . 12
3.2.1. Connections between Clients and Servers
(one-to-one) . . . . . . . . . . . . . . . . . . . . 13
3.2.2. Message Secrecy and Authentication . . . . . . . . . 13
4. Security Considerations . . . . . . . . . . . . . . . . . . . 16
4.1. Transport Security Links . . . . . . . . . . . . . . . . 16
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