How could the Bitcoin protocol be modified so that pruned nodes could still participate in BIP 37 SPV?

1

According to Jameson Lopp (https://www.coindesk.com/spv-support-billion-bitcoin-users-sizing-scaling-claim/), allowing pruned nodes to advertise that they support BIP 37 would be impossible without "extensive protocol changes." What changes would make this possible?

Ian MathWiz

Posted 2018-01-17T22:44:38.847

Reputation: 111

Answers

3

Pruned peers do not have the full blockchain history and therefore have only limited value for SPV clients.

With Bitcoin Core 0.16, pruned peers will announce their service via NODE_NETWORK_LIMITED (see BIP159). BIP159 is not a consensus change.

This will allow SPV clients to connect to pruned peers. But, since they only signal for the last 288 blocks, SPV/BIP37 clients interested to load history older than 1 day of blocks would still require to connect to traditional peers.

In the future, pruned nodes may have a way to signal how many blocks they will keep on disk (without adding a fingerprinting vulnerability).

Note that BIP37 is a controversial concept. It has significant privacy downsides (see Jonas Nick's research).

A far better concept is "Client side filtering". See the upcoming BIP157 and BIP158.

Jonas Schnelli

Posted 2018-01-17T22:44:38.847

Reputation: 5 718