Received-SPF: pass (sog-mx-3.v43.ch3.sourceforge.com: domain of petertodd.org
	designates 62.13.149.43 as permitted sender)
	client-ip=62.13.149.43; envelope-from=pete@petertodd.org;
	helo=outmail149043.authsmtp.co.uk; 
Date: Thu, 18 Apr 2013 05:28:24 -0400
From: Peter Todd <pete@petertodd.org>
To: Mike Hearn <mike@plan99.net>
Message-ID: <20130418092824.GA10184@savin>
References: <CANEZrP1yKeQMayFHsEUWtA3=q+v5rPAutjzEFVVHopPGNZ4jGQ@mail.gmail.com>
	<453bfc69-b2ab-4992-9807-55270fbda0db@email.android.com>
	<CANEZrP0z6W0ZDsytQ7Rcqb5L6rswn1wv8cbR7c383Dmpzu+gyg@mail.gmail.com>
	<CAPaL=UVJd3mdd0bs6Oo9vFHnv_6RbFowjmp0tD-ZbOzZxJEJ3g@mail.gmail.com>
	<CANEZrP3ocAJNoQ3xJqRTL8Gz3_T8xsCPPAvSfEOYpPo76wgbig@mail.gmail.com>
	<20130418090444.GA30995@savin>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha1;
	protocol="application/pgp-signature"; boundary="Qxx1br4bt0+wmkIi"
Content-Disposition: inline
In-Reply-To: <20130418090444.GA30995@savin>
User-Agent: Mutt/1.5.21 (2010-09-15)
Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Anti DoS for tx replacement
Precedence: list


--Qxx1br4bt0+wmkIi
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Thu, Apr 18, 2013 at 05:04:44AM -0400, Peter Todd wrote:
> An attack still shuts down useful tx replacement though. For instance in
> the adjusting payments example an attacker sets up a legit adjusting
> payment channel, does a bunch of adjustments, and then launches their
> attack. They broadcast enough adjustments that their adjustment session
> looks like part of an attack, and then don't have to pay for the full
> adjusted amount.

=2E..and actually, that's not a problem if the defender is online, because
they can just broadcast the highest sequence numbered tx, which blocks
further broadcasts by the attacker. You still need some way of
distinguishing the two acts, by time is probably fine, but it'd make a
real attack difficult.

Of course, regardless you are still asking nodes to set aside however
many KB/second to tx replacement transactions, and they're all going to
use different settings, which makes overall network convergence
impossible to guarantee as legit replacement transactions outnumber
non-legit ones. Any protocol requiring the broadcast of more than one or
two replacements, either normally or against an attacker, just isn't
going to be reliable. But many don't, so they're probably doable.


But lets see some working code first...

--=20
'peter'[:-1]@petertodd.org

--Qxx1br4bt0+wmkIi
Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: Digital signature

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.11 (GNU/Linux)

iQEcBAEBAgAGBQJRb7y3AAoJEH+rEUJn5PoEA7IH/AyhRVWdgLfet5//Wl3An3P1
qjtRZvAMFCQHB7Nx73TXHuZbMTXuQV4F2LsZB790sI0FE6vLFVKHhjov0g06a00X
YW9WNDkIXMOX3vVLRuhBMAaltrSZKE57q8z3ctkfMu0+21d2G4T9jpaoDKBrcm7u
o9h4HUni3WVB5mj9K9HgMZZQxFjAm4ozkGe3WrVY4+Z2iWGsfnaAIDtQ/IKnyUnQ
qTHgg7+OUjpZW0DgNrs9MHttFqipgeOrl66ogWC9SxLJ3oWlxnnYHq4JlCT9+r2C
J6mk3qrjQWCRdBDLzo6gP5+65ueivDPols6VXf7UNoRR2eNYd+RsGaXqgSfnC9M=
=Tsha
-----END PGP SIGNATURE-----

--Qxx1br4bt0+wmkIi--