Date: Tue, 28 Jun 2016 16:14:47 -0400
From: Peter Todd <pete@petertodd.org>
To: Eric Voskuil <eric@voskuil.org>
Message-ID: <20160628201447.GA1148@fedora-21-dvm>
References: <87h9cecad5.fsf@rustcorp.com.au>
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	<577234A4.3030808@jonasschnelli.ch>
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User-Agent: Mutt/1.5.23 (2014-03-12)
Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] BIP 151
Precedence: list


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On Tue, Jun 28, 2016 at 08:35:26PM +0200, Eric Voskuil wrote:
> Hi Peter,
>=20
> What in this BIP makes a MITM attack easier (or easy) to detect, or incre=
ases the probability of one being detected?

BIP151 gives users the tools to detect a MITM attack.

It's kinda like PGP in that way: lots of PGP users don't properly check key=
s,
so an attacker won't have a hard time MITM attacking those users. But some
users do check keys, a labor intensive manual process, but not a process th=
at
requires any real cryptographic sophistication, let alone writing any code.
It's very difficult for widescale attackers to distinguish the users who do
check keys from the ones that don't, so if you MITM attack _any_ user you r=
un
the risk of running into one of the few that does check, and those users can
alert everyone else.

The key thing, is we need to get everyones communications encrypted first: =
if
we don't the MITM attacker can intercept 99% of the communications with 0% =
risk
of detection, because the non-sophisticated users are trivially distinguish=
able
=66rom the sophisticated users: just find the users with unencrypted
communications!

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

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