Network-Based Website Fingerprinting
draft-wood-pearg-website-fingerprinting-00

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Last updated 2019-11-04
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pearg                                                        I. Goldberg
Internet-Draft                                    University of Waterloo
Intended status: Informational                                   T. Wang
Expires: May 7, 2020             HK University of Science and Technology
                                                                 C. Wood
                                                             Apple, Inc.
                                                       November 04, 2019

                  Network-Based Website Fingerprinting
               draft-wood-pearg-website-fingerprinting-00

Abstract

   The IETF is well on its way to protecting connection metadata with
   protocols such as DNS-over-TLS and DNS-over-HTTPS, and work-in-
   progress towards encrypting the TLS SNI.  However, more work is
   needed to protect traffic metadata, especially in the context of web
   traffic.  In this document, we survey Website Fingerprinting attacks,
   which are a class of attacks that use machine learning techniques to
   attack web privacy, and highlight metadata leaks used by said
   attacks.  We also survey proposed mitigations for such leakage and
   discuss their applicability to IETF protocols such as TLS, QUIC, and
   HTTP.  We endeavor to show that Website Fingerprinting attacks are a
   serious problem that affect all Internet users, and we pose open
   problems and directions for future research in this area.

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
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   This Internet-Draft will expire on May 7, 2020.

Goldberg, et al.           Expires May 7, 2020                  [Page 1]
Internet-Draft    Network-Based Website Fingerprinting     November 2019

Copyright Notice

   Copyright (c) 2019 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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Website Fingerprinting  . . . . . . . . . . . . . . . . . . .   4
   4.  Attacks . . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Base Rate Fallacy . . . . . . . . . . . . . . . . . . . . . .   8
   6.  Defenses  . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   7.  Open Problems and Directions  . . . . . . . . . . . . . . . .  12
   8.  Protocol Design Considerations  . . . . . . . . . . . . . . .  14
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   11. Informative References  . . . . . . . . . . . . . . . . . . .  14
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  20

1.  Introduction

   Internet protocols such as TLS 1.3 [RFC8446] and QUIC
   [I-D.ietf-quic-transport] bring substantial improvements to end-
   users.  The IETF engineered these with security and privacy in mind
   by encrypting more protocol messages using modern cryptographic
   primitives and algorithms, and engineering against flaws found in
   previous protocols, yielding several desirable security properties,
   including: forward-secure session key secrecy, downgrade protection,
   key compromise impersonation resistance, and protection of endpoint
   identities.  Combined, these two protocols are set to protect a
   significant amount of Internet data.  However, significant metadata
   leaks still exist for users of these protocols.  Examples include
   plaintext TLS SNI and application-specific extensions (ALPN), as well
   as DNS queries.  This information can be used by a passive attacker
   to learn information about the contents of an otherwise encrypted
   network connection.  Recently, such information has also been studied
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