Key Consistency and Discovery
draft-wood-key-consistency-00

Document Type Active Internet-Draft (individual)
Authors Alex Davidson  , Matthew Finkel  , Martin Thomson  , Christopher Wood 
Last updated 2021-02-22
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Network Working Group                                        A. Davidson
Internet-Draft                                                LIP Lisboa
Intended status: Informational                                 M. Finkel
Expires: 26 August 2021                                  The Tor Project
                                                              M. Thomson
                                                                 Mozilla
                                                               C.A. Wood
                                                              Cloudflare
                                                        22 February 2021

                     Key Consistency and Discovery
                     draft-wood-key-consistency-00

Abstract

   This document describes the key consistency and correctness
   requirements of protocols such as Privacy Pass, Oblivious DoH, and
   Oblivious HTTP for user privacy.  It discusses several mechanisms and
   proposals for enabling user privacy in varying threat models.  In
   concludes with discussion of open problems in this area.

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Discussion of this document takes place on the mailing list (), which
   is archived at .

   Source for this draft and an issue tracker can be found at
   https://github.com/chris-wood/key-consitency.

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
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 26 August 2021.

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Internet-Draft        Key Consistency and Discovery        February 2021

Copyright Notice

   Copyright (c) 2021 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
     1.1.  Requirements  . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Core Requirements . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Deploying Consistency and Correctness . . . . . . . . . . . .   4
     4.1.  Server-Provided Key Discovery . . . . . . . . . . . . . .   5
     4.2.  Proxy-Based Key Discovery . . . . . . . . . . . . . . . .   5
     4.3.  Log-Based Key Discovery . . . . . . . . . . . . . . . . .   6
     4.4.  Anonymous System Key Discovery  . . . . . . . . . . . . .   6
     4.5.  Consensus-based Key Discovery . . . . . . . . . . . . . .   6
     4.6.  Minimum Validity Periods  . . . . . . . . . . . . . . . .   7
   5.  Future Work . . . . . . . . . . . . . . . . . . . . . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

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1.  Introduction

   Several proposed privacy-enhancing protocols such as Privacy Pass
   [PRIVACY-PASS], Oblivious DoH [ODOH], and Oblivious HTTP [OHTTP]
   require clients to obtain and use a public key for execution.  For
   example, Privacy Pass public keys are used by clients for validating
   privately issued tokens for anonymous session resumption.  Oblivious
   DoH and HTTP both use public keys to encrypt messages to a particular
   server.  In all cases, a common security goal is that recipients
   cannot link usage of a public key to a specific (set of) user(s).  In
   other words, all users of a public key should belong to the same
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