Re: [Bitcoin-development] Peer Discovery and Overlay

2013-12-24 Thread Tier Nolan
On Tue, Dec 24, 2013 at 8:52 AM, Jeremy Spilman jer...@taplink.co wrote:

 Are there any past instances of applications hijacking or interfacing with
 the exiting p2p messages, or abusing 'getaddr' functionality? Are there
 any guidelines on this, or should there be?


There was a BIP by Stefan Thomas for adding custom services to the
protocol.  Discovery would be helpful here too.  If this was added, it
wouldn't be intended for use in a hostile way though.

This one was the custom services BIP.  It defines a change to the version
message and also custom sub-commands.
https://github.com/bitcoin/bips/blob/master/bip-0036.mediawiki

This one discusses how network discovery should be handles.
https://en.bitcoin.it/wiki/User:Justmoon/BIP_Draft:_Custom_Service_Discovery
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Re: [Bitcoin-development] Peer Discovery and Overlay

2013-12-24 Thread Peter Todd
On Tue, Dec 24, 2013 at 12:52:46AM -0800, Jeremy Spilman wrote:
 Some really nice efforts out there to map and analyze the bitcoin P2P  
 network.
 
 The current protocol apparently recommends returning up to 2500 addresses  
  from 'getaddr'. I'm not sure how much clients are expected to probe the  
 address space in order to select 'far-apart' peers, or how much such an  
 process would even attempt to achieve.

The logic is that by simply connecting to peers at random you keep the
network structure as a whole randomized. You don't need to make any
specific attempt at connecting to far-apart peers.

 How much does it matter if the ability to discover the entire network of  
 peers is fast or slow? There are probably pros and cons to both.
 
 Is there any thought to how existing bitcoin node relations, and the ease  
 at which peers can be discovered, becomes a service in itself, or even  
 possibly a vulnerability?

Keep in mind it's easy for better knowledge of the network to be a
vulnerability; the number of full nodes is small enough that DoS
attacking all of them is quite feasible.

The other big vulnerability is that getaddr data is best effort; we
currently have no mechanism to ensure that nodes are in fact operated by
separate individuals. It'd be quite easy for someone to set up a
relatively small number of nodes that only advertise themselves in the
getaddr information. Over time they would get proportionally more
incoming connections than is fair

As for node addresses being a service, that's what the DNS seeds are!
bitcoinj clients, for instance, depend very heavily on those seeds and
can be easily compromised in a variety of ways by them.

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Re: [Bitcoin-development] Peer Discovery and Overlay

2013-12-24 Thread Warren Togami Jr.
I was concerned about this issue so we sponsored BlueMatt to implement an
address database for bitcoinj.  In the future it won't be entirely reliant
on what DNS tells it.

Warren

On Tue, Dec 24, 2013 at 6:02 AM, Peter Todd p...@petertodd.org wrote:

 As for node addresses being a service, that's what the DNS seeds are!
 bitcoinj clients, for instance, depend very heavily on those seeds and
 can be easily compromised in a variety of ways by them.

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Re: [Bitcoin-development] Peer Discovery and Overlay

2013-12-24 Thread Mike Hearn
Thanks Warren! That's great. It's also a prerequisite for chain pruning, so
it's not only about decentralisation but also scalability.

Looking forward to reviewing and merging that.


On Tue, Dec 24, 2013 at 6:11 PM, Warren Togami Jr. wtog...@gmail.comwrote:

 I was concerned about this issue so we sponsored BlueMatt to implement an
 address database for bitcoinj.  In the future it won't be entirely reliant
 on what DNS tells it.

 Warren


 On Tue, Dec 24, 2013 at 6:02 AM, Peter Todd p...@petertodd.org wrote:

 As for node addresses being a service, that's what the DNS seeds are!
  bitcoinj clients, for instance, depend very heavily on those seeds and
 can be easily compromised in a variety of ways by them.



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