Date: Tue, 28 Jun 2016 14:22:02 -0400
From: Peter Todd <pete@petertodd.org>
To: Eric Voskuil <eric@voskuil.org>,
	Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Message-ID: <20160628182202.GA5519@fedora-21-dvm>
References: <87h9cecad5.fsf@rustcorp.com.au>
	<1E86A00F-0609-4DBC-9543-94AE04CC13C9@voskuil.org>
	<577234A4.3030808@jonasschnelli.ch>
	<360EF9B8-A174-41CA-AFDD-2BC2C0B4DECB@voskuil.org>
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In-Reply-To: <360EF9B8-A174-41CA-AFDD-2BC2C0B4DECB@voskuil.org>
User-Agent: Mutt/1.5.23 (2014-03-12)
Subject: Re: [bitcoin-dev] BIP 151
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On Tue, Jun 28, 2016 at 06:45:58PM +0200, Eric Voskuil via bitcoin-dev wrot=
e:
> > 1) Transaction censorship
> > ISPs, WIFI provider or any other MITM, can holdback/censor unconfirmed
> > transactions. Regardless if you are a miner or a validation/wallet node.
> >=20
> > 2) Peer censorship
> > MITM can remove or add entries from a "addr" message.
> >=20
> > 3) Fingerprinting
> > ISPs or any other MITM can intercept/inject fingerprinting relevant
> > messages like "mempool" to analyze the bitcoin network.
>=20
> Encryption alone cannot protect against a MITM attack in an anonymous and=
 permissionless network. This is accepted in the BIP (and your follow-up re=
ply).

Being able to easily detect MITM attacks is a _huge_ step forward that
shouldn't be underestimated; even if 99% of users aren't in a position to
detect the MITM you only need a small subset of users that do the necessary
checks to alert the wider community, who can then respond with stronger
security measures. Those measures are likely to be more costly - authentica=
ted
systems are significantly harder than not - so better to save your efforts
until the need for them is more obvious.

Also the fact that an attack has a reasonable probability of detection is a=
 big
disincentive for many types of attackers - note how one of the things revea=
led
in the Snowden leaks was the fact that the NSA generally tries quite hard to
avoid tipping off targets to the fact that they're being surveilled, with a
myriad of carefully scripted policies to control when and how exploits are =
used
against targets.

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

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