TLS Client Puzzles Extension
draft-nygren-tls-client-puzzles-02

Document Type Active Internet-Draft (individual)
Last updated 2016-12-25
Stream (None)
Intended RFC status (None)
Formats plain text xml pdf html bibtex
Stream Stream state (No stream defined)
Consensus Boilerplate Unknown
RFC Editor Note (None)
IESG IESG state I-D Exists
Telechat date
Responsible AD (None)
Send notices to (None)
Network Working Group                                          E. Nygren
Internet-Draft                                                    S. Erb
Intended status: Standards Track                     Akamai Technologies
Expires: July 1, 2017                                        A. Biryukov
                                                         D. Khovratovich
                                                University of Luxembourg
                                                                A. Juels
                                                      Cornell University
                                                       December 28, 2016

                      TLS Client Puzzles Extension
                   draft-nygren-tls-client-puzzles-02

Abstract

   Client puzzles allow a TLS server to defend itself against asymmetric
   DDoS attacks.  In particular, it allows a server to request clients
   perform a selected amount of computation prior to the server
   performing expensive cryptographic operations.  This allows servers
   to employ a layered defense that represents an improvement over pure
   rate-limiting strategies.

   Client puzzles are implemented as an extension to TLS 1.3
   [I-D.ietf-tls-tls13] wherein a server can issue a HelloRetryRequest
   containing the puzzle as an extension.  The client must then resend
   its ClientHello with the puzzle results in the extension.

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 http://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."

   This Internet-Draft will expire on July 1, 2017.

Nygren, et al.            Expires July 1, 2017                  [Page 1]
Internet-Draft               Client Puzzles                December 2016

Copyright Notice

   Copyright (c) 2016 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
   (http://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.  Overview and rationale  . . . . . . . . . . . . . . . . . . .   2
   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . .   3
   3.  Handshake Changes . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  The ClientPuzzleExtension Message . . . . . . . . . . . .   5
   4.  Usage by Servers  . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Proposed Client Puzzles . . . . . . . . . . . . . . . . . . .   6
     5.1.  Cookie Client Puzzle Type . . . . . . . . . . . . . . . .   7
     5.2.  SHA-256 CPU Puzzle Type . . . . . . . . . . . . . . . . .   7
     5.3.  SHA-512 CPU Puzzle Type . . . . . . . . . . . . . . . . .   8
     5.4.  Equihash: Memory-hard Generalized Birthday Problem Puzzle
           Type  . . . . . . . . . . . . . . . . . . . . . . . . . .   8
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   8.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  11
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  11
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     10.2.  Informative References . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Overview and rationale

   Adversaries can exploit the design of the TLS protocol to craft
   powerful asymmetric DDOS attacks.  Once an attacker has opened a TCP
   connection, the attacker can transmit effectively static content that
   causes the server to perform expensive cryptographic operations.
   Rate limiting offers one possible defense against this type of
   attack; however, pure rate limiting systems represent an incomplete
Show full document text