public inbox for bitcoindev@googlegroups.com
 help / color / mirror / Atom feed
From: Gregory Maxwell <greg@xiph.org>
To: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
Subject: [bitcoin-dev] Getting around to fixing the timewarp attack.
Date: Mon, 20 Aug 2018 20:14:50 +0000	[thread overview]
Message-ID: <CAAS2fgRo5k8yBKXub46q7SQutskPKPmv5sXPZcM5+E_yzW5_mQ@mail.gmail.com> (raw)

Since 2012 (IIRC) we've known that Bitcoin's non-overlapping
difficulty calculation was vulnerable to gaming with inaccurate
timestamps to massively increase the rate of block production beyond
the system's intentional design. It can be fixed with a soft-fork that
further constraints block timestamps, and a couple of proposals have
been floated along these lines.

I put a demonstration of timewarp early in the testnet3 chain to also
let people test mitigations against that.  It pegs the difficulty way
down and then churned out blocks at the maximum rate that the median
time protocol rule allows.

I, and I assume others, haven't put a big priority into fixing this
vulnerability because it requires a majority hashrate and could easily
be blocked if someone started using it.

But there haven't been too many other network consensus rules going on
right now, and I believe at least several of the proposals suggested
are fully compatible with existing behaviour and only trigger in the
presence of exceptional circumstances-- e.g. a timewarp attack.  So
the risk of deploying these mitigations would be minimal.

Before I dust off my old fix and perhaps prematurely cause fixation on
a particular approach, I thought it would be useful to ask the list if
anyone else was aware of a favourite backwards compatible timewarp fix
proposal they wanted to point out.

Cheers.


             reply	other threads:[~2018-08-20 20:15 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-20 20:14 Gregory Maxwell [this message]
2018-08-22 13:48 ` [bitcoin-dev] Getting around to fixing the timewarp attack Jorge Timón
2018-08-24  9:35 ` Johnson Lau
2018-08-30 20:55   ` Bram Cohen
2018-08-29  9:54 Zawy

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CAAS2fgRo5k8yBKXub46q7SQutskPKPmv5sXPZcM5+E_yzW5_mQ@mail.gmail.com \
    --to=greg@xiph.org \
    --cc=bitcoin-dev@lists.linuxfoundation.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox