Hi all,
I think I discovered an interesting form of sabotage attack (possible for miners) that tries to create coordination disincentives among Bitcoin users - named after the dystopian movie The Purge, where all crime is legal for one night every year.
TLDR
* An attacker replaces the most recent blocks full of transactions with empty blocks.
* Previously confirmed txns return into the mempool, where anyone with a minimum of technical knowledge or access to public tools can opportunistically double-spend their txns back to themselves. (the process is the same as double-spending regular zero-conf txns)
The attack seems useful to undermine trust in Bitcoin's assurances, e.g. the future finality of transactions. It differs from other forms of sabotage (e.g. DoS by mining only empty blocks) in that it specifically disrupts the coordination process among users in response to the attack.
By giving some users a chance to benefit from the attack, the attacker gives them a vested interest in staying on the attack chain. If enough users accept the invitation to double-spend, it might become harder to come to consensus on how to deal with the attack.
Purge attacks probably don’t constitute a bigger risk than other known forms of sabotage attacks, but seem like an interesting spin where the attacker specifically targets the pre-coordination of defenders.
You can find the full report, incl. some mitigations against sabotage attacks, at
https://blog.deribit.com/insights/destabilizing-bitcoin-consensus-with-purge-attacks/Your feedback is highly appreciated.
Regards,
Hasu