BIP Editor: Can I get a BIP # for this?
On 08/21/15 17:55, Matt Corallo via bitcoin-dev wrote: > Revised copy follows. re: mentioning the HTTP seeding stuff, I'm not > sure we want to encourage more people aside from bitcoinj to use > that...I thought about adding a DNS seed section to this bip, but > decided against it...still, I think we should add the option to select > service bits to DNS seeds ASAP. > > Re: need to "shard" the blockchain: not sure what you're referring to > here. The bloom filter stuff requires you to download the chain > in-order, sure, but you have to do that for headers anyway, and > hopefully your total data isnt too much more than headers alone. > > Anyone have the best reference for the DoS issues? > > BIP: ? > Title: NODE_BLOOM service bit > Author: Matt Corallo <b...@bluematt.me>, Peter Todd <p...@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. > > > > On 08/21/15 05:42, Peter Todd wrote: >> On Thu, Aug 20, 2015 at 10:38:19PM -0700, Peter Todd via bitcoin-dev wrote: >>>> 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. >>> >>> I'd reference that paper on bloom filters re: the "little to no privacy" >>> issue. There's also a post in the bitcoinj mailing list somewhere IIRC >>> talking about the default settings, and how they don't provide any >>> privacy. >> >> Oh, and we should also point out that Bloom filters have scaling issues, >> as each application of the filter has to scan the whole blockchain - >> with future blocksize increases these issues increase, in some proposals >> quite dramatically. The underlying idea also conflicts with some >> proposals to "shard" the blockchain, again suggesting that we need a bit >> to handle future upgrades to more scalable designs. >> > _______________________________________________ > bitcoin-dev mailing list > bitcoin-dev@lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev > _______________________________________________ bitcoin-dev mailing list bitcoin-dev@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
