Privacy Pass: The Protocol
draft-davidson-pp-protocol-00

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Network Working Group                                        A. Davidson
Internet-Draft                                       Cloudflare Portugal
Intended status: Informational                              9 March 2020
Expires: 10 September 2020

                       Privacy Pass: The Protocol
                     draft-davidson-pp-protocol-00

Abstract

   This document specifies the Privacy Pass protocol for privacy-
   preserving authorization of clients to servers.  The privacy
   requirement is that client re-authorization events cannot be linked
   to any previous initial authorization.  Privacy Pass is intended to
   be used as a performant protocol in the Internet setting.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 10 September 2020.

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
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   provided without warranty as described in the Simplified BSD License.

Davidson                Expires 10 September 2020               [Page 1]
Internet-Draft                 PP protocol                    March 2020

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Layout  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Preliminaries . . . . . . . . . . . . . . . . . . . . . . . .   5
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   5
     2.2.  Basic assumptions . . . . . . . . . . . . . . . . . . . .   5
   3.  Privacy Pass functional API . . . . . . . . . . . . . . . . .   6
     3.1.  Data structures . . . . . . . . . . . . . . . . . . . . .   6
       3.1.1.  Ciphersuite . . . . . . . . . . . . . . . . . . . . .   6
       3.1.2.  ServerConfig  . . . . . . . . . . . . . . . . . . . .   6
       3.1.3.  ServerUpdate  . . . . . . . . . . . . . . . . . . . .   7
       3.1.4.  ClientConfig  . . . . . . . . . . . . . . . . . . . .   7
       3.1.5.  ClientIssuanceInput . . . . . . . . . . . . . . . . .   7
       3.1.6.  IssuanceMessage . . . . . . . . . . . . . . . . . . .   8
       3.1.7.  IssuanceResponse  . . . . . . . . . . . . . . . . . .   8
       3.1.8.  RedemptionToken . . . . . . . . . . . . . . . . . . .   8
       3.1.9.  RedemptionMessage . . . . . . . . . . . . . . . . . .   9
       3.1.10. RedemptionResponse  . . . . . . . . . . . . . . . . .   9
     3.2.  API functions . . . . . . . . . . . . . . . . . . . . . .   9
       3.2.1.  PP_Server_Setup . . . . . . . . . . . . . . . . . . .   9
       3.2.2.  PP_Client_Setup . . . . . . . . . . . . . . . . . . .  10
       3.2.3.  PP_Generate . . . . . . . . . . . . . . . . . . . . .  10
       3.2.4.  PP_Issue  . . . . . . . . . . . . . . . . . . . . . .  10
       3.2.5.  PP_Process  . . . . . . . . . . . . . . . . . . . . .  11
       3.2.6.  PP_Redeem . . . . . . . . . . . . . . . . . . . . . .  11
       3.2.7.  PP_Verify . . . . . . . . . . . . . . . . . . . . . .  12
     3.3.  Error types . . . . . . . . . . . . . . . . . . . . . . .  12
   4.  Generalized protocol overview . . . . . . . . . . . . . . . .  12
     4.1.  Key initialisation phase  . . . . . . . . . . . . . . . .  13
     4.2.  Issuance phase  . . . . . . . . . . . . . . . . . . . . .  14
     4.3.  Redemption phase  . . . . . . . . . . . . . . . . . . . .  14
       4.3.1.  Double-spend protection . . . . . . . . . . . . . . .  15
     4.4.  Handling errors . . . . . . . . . . . . . . . . . . . . .  16
   5.  Security requirements . . . . . . . . . . . . . . . . . . . .  16
     5.1.  Unlinkability . . . . . . . . . . . . . . . . . . . . . .  16
     5.2.  One-more unforgeability . . . . . . . . . . . . . . . . .  17
     5.3.  Double-spend protection . . . . . . . . . . . . . . . . .  18
   6.  VOPRF instantiation . . . . . . . . . . . . . . . . . . . . .  18
     6.1.  VOPRF conventions . . . . . . . . . . . . . . . . . . . .  18
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