Date: Thu, 20 Aug 2015 22:42:19 -0700
From: Peter Todd <pete@petertodd.org>
To: Matt Corallo <lf-lists@mattcorallo.com>,
	bitcoin-dev@lists.linuxfoundation.org
Message-ID: <20150821054219.GB18176@muck>
References: <55D6AD19.10305@mattcorallo.com>
 <20150821053819.GA18176@muck>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha256;
	protocol="application/pgp-signature"; boundary="dc+cDN39EJAMEtIO"
Content-Disposition: inline
In-Reply-To: <20150821053819.GA18176@muck>
Subject: Re: [bitcoin-dev] Revisiting NODE_BLOOM: Proposed BIP
Precedence: list


--dc+cDN39EJAMEtIO
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Thu, Aug 20, 2015 at 10:38:19PM -0700, Peter Todd via bitcoin-dev wrote:
> > Motivation
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> >=20
> > BIP 37 did not specify a service bit for the bloom filter service, thus
> > implicitly assuming that all nodes that serve peers data support it.
> > However, the connection filtering algorithm proposed in BIP 37, and
> > implemented in several clients today, has been shown to provide little
> > to no privacy, as well as being a large DoS risk on some nodes. Thus,
> > allowing node operators to disable connection bloom filtering is a
> > much-needed feature.
>=20
> I'd reference that paper on bloom filters re: the "little to no privacy"
> issue. There's also a post in the bitcoinj mailing list somewhere IIRC
> talking about the default settings, and how they don't provide any
> privacy.

Oh, and we should also point out that Bloom filters have scaling issues,
as each application of the filter has to scan the whole blockchain -
with future blocksize increases these issues increase, in some proposals
quite dramatically. The underlying idea also conflicts with some
proposals to "shard" the blockchain, again suggesting that we need a bit
to handle future upgrades to more scalable designs.

--=20
'peter'[:-1]@petertodd.org
00000000000000000402fe6fb9ad613c93e12bddfc6ec02a2bd92f002050594d

--dc+cDN39EJAMEtIO
Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: Digital signature

-----BEGIN PGP SIGNATURE-----
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==
=5hyw
-----END PGP SIGNATURE-----

--dc+cDN39EJAMEtIO--