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Date: Thu, 27 Nov 2014 11:27:34 +0000
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From: Wladimir <laanwj@gmail.com>
To: Gregory Maxwell <gmaxwell@gmail.com>
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Cc: Bitcoin Development <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Deanonymisation of clients in Bitcoin P2P
 network paper
Precedence: list

On Thu, Nov 27, 2014 at 2:22 AM, Gregory Maxwell <gmaxwell@gmail.com> wrote:
>> Since this attack vector has been discussed, I started making some
>> measurements on how effective it is to connect to Bitcoin using Tor,
>> and I found that the number of connections dropping to near-zero is
>> a situation which occurs rather frequently, which suggests that there
>> is still room to improve on the DoS handling.
>
> I'm confused by this, I run quite a few nodes exclusively on tor and
> chart their connectivity and have seen no such connection dropping
> behaviour.

In my experience the problem has always been getting bootstrapped.
Most nodes hardly give any hidden service nodes in their getaddr.
(this has been improved in master by including a set of hidden service
seed nodes)
But this assumes -onlynet=tor. Tor with exit nodes should be less
problematic, unless someone managed to DoSban all the exit nodes as
described in the paper (but I've never seen such an attack myself).

> Can you tell me more about how you measured this?
>
> [As an aside I agree that there are lots of things to improve here,
> but the fact that users can in theory be forced off of tor via DOS
> attacks is not immediately concerning to me because its a conscious
> choice users would make to abandon their privacy (and the behaviour of
> the system here is known and intentional). There are other mechanisms
> available for people to relay their transactions than connecting
> directly to the bitcoin network; so their choice isn't just abandon
> privacy or don't use bitcoin at all.]

Right, there's something to be said for splitting your own transaction
submission from normal P2P networking and transaction relay.
(esp for non-SPV wallets which don't inherently leak any information
about their addresses)

There was a pull request about this for Bitcoin Core one, maybe I
closed it unfairly https://github.com/bitcoin/bitcoin/issues/4564 .

Wladimir