Subject: Re: [bitcoin-dev] Revisiting NODE_BLOOM: Proposed BIP

From: Matt Corallo <[email-masked]>
Date: Fri, 21 Aug 2015 17:53:34 +0000

The proposal will not break any existing clients in the first release.
After sufficient time to upgrade SPV clients, a new version will be
released which will result in older SPV clients finding themselves
disconnected from peers when they send filter* commands, so they can go
find other peers which do support bloom filtering.

On 08/21/15 05:48, Jeff Garzik wrote:
> If this is widely deployed + enabled, what is the impact to current
> wallets in use?
> 
> 
> On Fri, Aug 21, 2015 at 12:46 AM, Matt Corallo via bitcoin-dev
> <[email-masked]
> <mailto:[email-masked]>> wrote:
> 
>     Peter: Since I stole most of this text from your old BIP, should I leave
>     you as an author?
> 
>     BIP: ?
>     Title: NODE_BLOOM service bit
>     Author: Matt Corallo <[email-masked] <mailto:[email-masked]>>,
>     Peter Todd <[email-masked] <mailto:[email-masked]>>
>     Type: Standards Track (draft)
>     Created: 20-08-2015
> 
>     Abstract
>     ========
> 
>     This BIP extends BIP 37, Connection Bloom filtering, by defining a
>     service bit to allow peers to advertise that they support bloom filters
>     explicitly. It also bumps the protocol version to allow peers to
>     identify old nodes which allow bloom filtering of the connection despite
>     lacking the new service bit.
> 
> 
>     Motivation
>     ==========
> 
>     BIP 37 did not specify a service bit for the bloom filter service, thus
>     implicitly assuming that all nodes that serve peers data support it.
>     However, the connection filtering algorithm proposed in BIP 37, and
>     implemented in several clients today, has been shown to provide little
>     to no privacy, as well as being a large DoS risk on some nodes. Thus,
>     allowing node operators to disable connection bloom filtering is a
>     much-needed feature.
> 
> 
>     Specification
>     =============
> 
>     The following protocol bit is added:
> 
>         NODE_BLOOM = (1 << 2)
> 
>     Nodes which support bloom filters should set that protocol bit.
>     Otherwise it should remain unset. In addition the protocol version is
>     increased from 70002 to 70011 in the reference implementation. It is
>     often the case that nodes which have a protocol version smaller than
>     70011, but larger than 70000 support bloom filtered connections without
>     the NODE_BLOOM bit set, however clients which require bloom filtered
>     connections should avoid making this assumption.
> 
>     NODE_BLOOM is distinct from NODE_NETWORK, and it is legal to advertise
>     NODE_BLOOM but not NODE_NETWORK (eg for nodes running in pruned mode
>     which, nonetheless, provide filtered access to the data which they
>     do have).
> 
>     If a node does not support bloom filters but receives a "filterload",
>     "filteradd", or "filterclear" message from a peer the node should
>     disconnect that peer immediately. For backwards compatibility, in
>     initial implementations, nodes may choose to only disconnect nodes which
>     have the new protocol version set and attempt to send a filter command.
> 
>     While outside the scope of this BIP it is suggested that DNS seeds and
>     other peer discovery mechanisms support the ability to specify the
>     services required; current implementations simply check only that
>     NODE_NETWORK is set.
> 
> 
>     Design rational
>     ===============
> 
>     A service bit was chosen as applying a bloom filter is a service.
> 
>     The increase in protocol version is for backwards compatibility. In
>     initial implementations, old nodes which are not yet aware of NODE_BLOOM
>     and use a protocol version < 70011 may still send filter* messages to a
>     node without NODE_BLOOM. This feature may be removed after there are
>     sufficient NODE_BLOOM nodes available and SPV clients have upgraded,
>     allowing node operators to fully close the bloom-related DoS vectors.
> 
> 
>     Reference Implementation
>     ========================
> 
>     https://github.com/bitcoin/bitcoin/pull/6579
> 
> 
>     Copyright
>     =========
> 
>     This document is placed in the public domain.
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>