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From: Eric Voskuil <eric@voskuil.org>
In-Reply-To: <20160628182202.GA5519@fedora-21-dvm>
Date: Tue, 28 Jun 2016 20:35:26 +0200
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References: <87h9cecad5.fsf@rustcorp.com.au>
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To: Peter Todd <pete@petertodd.org>
Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] BIP 151
Precedence: list

Hi Peter,

What in this BIP makes a MITM attack easier (or easy) to detect, or increase=
s the probability of one being detected?

e

> On Jun 28, 2016, at 8:22 PM, Peter Todd <pete@petertodd.org> wrote:
>=20
> On Tue, Jun 28, 2016 at 06:45:58PM +0200, Eric Voskuil via bitcoin-dev wro=
te:
>>> 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 rep=
ly).
>=20
> 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 necessar=
y
> checks to alert the wider community, who can then respond with stronger
> security measures. Those measures are likely to be more costly - authentic=
ated
> systems are significantly harder than not - so better to save your efforts=

> until the need for them is more obvious.
>=20
> 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 reve=
aled
> in the Snowden leaks was the fact that the NSA generally tries quite hard t=
o
> 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
> --=20
> https://petertodd.org 'peter'[:-1]@petertodd.org