Add last-fully-posted version of BIP 111

bip-0111.mediawiki

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+BIP: 111
+Title: NODE_BLOOM service bit
+Author: Matt Corallo <bip@bluematt.me>, Peter Todd <pete@petertodd.org>
+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[1], as well as being a large DoS risk on some nodes[2].
+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.
+
+
+References
+==========
+
+[1] http://eprint.iacr.org/2014/763
+[2] ???? is one example where the issues were found, though others
+independently discovered issues as well. Sample DoS exploit code
+available at https://github.com/petertodd/bloom-io-attack.