Chain width expansion DoS

[braydonf]

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.

The complete paper:
https://bcoin.io/papers/bitcoin-chain-expansion.pdf

Further discussion:
https://www.mail-archive.com/[email protected]/msg08391.html

The branch:
https://github.com/bcoin-org/bcoin/tree/chain-expansion

[braydonf]

Related time warp issue #925 that should be considered in relation to chain width expansion. It's further discussed on the mailing list.