[bitcoin-dev] Chain width expansion

[Braydon Fuller]

Hi everyone,

We would like to share a paper for broad discussion, it is titled
"Bitcoin Chain Width Expansion Denial-of-Service Attacks".

>From the abstract: The attacks leverage unprotected resources for a
denial-of-service by filling the disk and exhausting the CPU with
unnecessary header and block data. This forces the node to halt
operation. The attack difficulty ranges from difficult to easy. There
are currently limited guards for some of the attacks that require
checkpoints to be enabled. This paper describes a solution that does not
require enabling or maintaining checkpoints and provides improved security.

As the checkpoints in Bitcoin Core have not been maintained or updated
since mid 2014, this is especially relevant. Bitcoin Core implements
headers-first synchronization, since 2014, that provides the base for
the further improvements upon that design.

The paper is available at:
https://bcoin.io/papers/bitcoin-chain-expansion.pdf

The proposed solution has been implemented in Bcoin and is available at:
https://github.com/bcoin-org/bcoin/tree/chain-expansion

Best,
Braydon Fuller