[bitcoin-dev] A design for Probabilistic Partial Pruning
David A. Harding
dave at dtrt.org
Sat Feb 27 19:19:34 UTC 2021
On Fri, Feb 26, 2021 at 11:40:35AM -0700, Keagan McClelland via bitcoin-dev wrote:
> Hi all,
> 4. Once the node's IBD is complete it would advertise this as a peer
> service, advertising its seed and threshold, so that nodes could
> deterministically deduce which of its peers had which blocks.
Although some of the details differed, I believe this general idea of
sharded block storage was previously discussed in the context of BIP159,
"Peers may have different prune depths (depending on the peers
configuration, disk space, etc.) which can result in a
fingerprinting weakness (finding the prune depth through getdata
requests). NODE_NETWORK_LIMITED supporting peers SHOULD avoid
leaking the prune depth and therefore not serve blocks deeper than
the signaled NODE_NETWORK_LIMITED threshold (288 blocks)."
- BIP: https://github.com/bitcoin/bips/blob/master/bip-0159.mediawiki#counter-measures-for-peer-fingerprinting
- Discussion thread 1: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-April/014186.html
- Discussion thread 2: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-May/014314.html
- Discussion thread 2, continued: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-April/014186.html
- BIP159-related PR, review comments: https://github.com/bitcoin/bitcoin/pull/10387
> If you have thoughts on
> A. The protocol design itself
> B. The barriers to put this kind of functionality into Core
> I would love to hear from you,
I think it would be unlikely for any popular node software to adopt a
technique that could make specific nodes easily fingerprintable on an
ongoing basis unless it solved some other urgent problem. Luke Dashjr's
rough data collection currently shows 5,629 archival listening nodes,
which is a substantial fraction of the roughly 10,000 listening nodes
reported by Addy Yeow, so I don't think we're near the point of
needing to worry about the unavailability of historic blocks.
However, if there's a reasonable solution to the fingerprinting problem,
I do think node developers would find that very interesting.
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