Gossiping in CT
draft-linus-trans-gossip-ct-01

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Last updated 2015-03-09
Replaced by draft-ietf-trans-gossip
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TRANS                                                        L. Nordberg
Internet-Draft                                                  NORDUnet
Intended status: Experimental                                 D. Gillmor
Expires: September 10, 2015                                         ACLU
                                                          March 09, 2015

                            Gossiping in CT
                     draft-linus-trans-gossip-ct-01

Abstract

   This document describes two gossiping mechanisms for Certificate
   Transparency [RFC6962]; SCT feedback and STH gossip.  In order for
   HTTPS clients to share SCTs with CT auditors in a privacy-preserving
   manner they send SCTs to originating HTTP servers which in turn share
   the SCTs with CT auditors.  CT auditors and monitors share STHs among
   each other.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on September 10, 2015.

Copyright Notice

   Copyright (c) 2015 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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   include Simplified BSD License text as described in Section 4.e of

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Problem . . . . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Who should gossip . . . . . . . . . . . . . . . . . . . . . .   3
   3.  What to gossip about and how  . . . . . . . . . . . . . . . .   3
     3.1.  SCT feedback  . . . . . . . . . . . . . . . . . . . . . .   3
       3.1.1.  HTTPS client to server  . . . . . . . . . . . . . . .   3
       3.1.2.  HTTPS server to auditors  . . . . . . . . . . . . . .   4
       3.1.3.  SCT feedback data format  . . . . . . . . . . . . . .   5
     3.2.  STH gossip  . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Security considerations . . . . . . . . . . . . . . . . . . .   6
     4.1.  Privacy considerations  . . . . . . . . . . . . . . . . .   6
       4.1.1.  Privacy and SCTs  . . . . . . . . . . . . . . . . . .   7
       4.1.2.  Privacy in SCT feedback . . . . . . . . . . . . . . .   7
       4.1.3.  Privacy in STH gossip . . . . . . . . . . . . . . . .   7
   5.  IANA considerations . . . . . . . . . . . . . . . . . . . . .   8
   6.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   8
   7.  ChangeLog . . . . . . . . . . . . . . . . . . . . . . . . . .   8
     7.1.  Changes between -00 and -01 . . . . . . . . . . . . . . .   8
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Problem

   Public append-only untrusted logs have to be monitored for
   consistency, i.e. that they should never rewrite history.  Monitors
   and other log clients need to exchange information about monitored
   logs in order to be able to detect a partitioning attack.

   A partitioning attack is when a log serves different views of the log
   to different clients.  Each client would be able to verify the
   append-only nature of the log while in the extreme case being the
   only client seeing this particular view.

   Gossiping about what's known about logs helps solving the problem of
   detecting malicious or compromised logs mounting such a partitioning
   attack.  We want some side of the partitioned tree, and ideally both
   sides, to see the other side.

   Disseminating known information about a log poses a potential threat
   to the privacy of end users.  Gossiping about data which is linkable
   to a specific log entry and by that to a specific site has to take
   privacy considerations into account in order not to leak sensitive
   information.

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