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Date: Fri, 6 Jun 2014 05:11:34 -0400
From: Peter Todd <pete@petertodd.org>
To: Gregory Maxwell <gmaxwell@gmail.com>
Message-ID: <20140606091134.GA23205@savin>
References: <20140606081933.GA29458@savin>
	<20140606084852.GA30247@netbook.cypherspace.org>
	<CAAS2fgTsjZPxds+QHb+ceC_Thu4xsDFAEqXtxznCs_EbyLZepg@mail.gmail.com>
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Cc: Bitcoin Development <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] NODE_BLOOM service bit
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On Fri, Jun 06, 2014 at 02:03:29AM -0700, Gregory Maxwell wrote:
> On Fri, Jun 6, 2014 at 1:48 AM, Adam Back <adam@cypherspace.org> wrote:
> > Advertising NODE BLOOM as a service sounds good.
> >
> > But the critique of bloom filters, I am not so sure prefix filters are
> > better.  Prefix filters offer questionable privacy tradeoffs in my opin=
ion.
> > Same problem as with stealth address proposed use of prefixes.
> >
> > All for scalability, efficiency and decentralization but not ideally at=
 the
> > expense of nuking privacy.  The effects on privacy are cumulative, and
> > affect everyone not just the user.  Same pattern of local decision, glo=
bal
> > effect as with reused addresses.
>=20
> The performance Bytecoin/Monero/Fantom/etc. systems that use ECDH
> addresses for all transactions seem to be suggesting that the prefixes
> aren't really needed.
>=20
> At least with current system rules doing the ECDH for each transaction
> seems pretty reasonable.

Yup. Obelisk's indexing is sufficiently fast that they hadn't even
bothered making Dark Wallet store transaction information between
sessions until recently. Prefix brute-forcing isn't yet implemented,
although prefix filters is being implemented for lookups in general. (at
the very least it gives the server operators some valuable plausible
deniability)

--=20
'peter'[:-1]@petertodd.org
00000000000000003a68ee16d702ca5dd5547fb4aead910a004747cb06241dd6

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