Subject: Re: [Bitcoin-development] NODE_BLOOM service bit

From: Peter Todd <[email-masked]>
Date: Fri, 6 Jun 2014 05:11:34 -0400

On Fri, Jun 06, 2014 at 02:03:29AM -0700, Gregory Maxwell wrote:
> On Fri, Jun 6, 2014 at 1:48 AM, Adam Back <[email-masked]> 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 opinion.
> > 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, global
> > effect as with reused addresses.
> 
> 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.
> 
> 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)

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