Since I raised this with Hasu in early Jan[0], I've been looking for ways
to eliminate transaction replacement that are consensus compatible (since
first safe seen is not). The best I could come up with is "Uncontested
Safe", which I've tried to sketch out in a brief medium article[1].

Am I retracing steps? Feedback would be appreciated.

[0] https://twitter.com/mikekelly85/status/1217590668735983622
[1] https://medium.com/@mikekelly85/uncontested-safe-protocol-e5af8c145f1

Cheers,
M

On Sat, Feb 1, 2020 at 10:12 PM ha su via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> 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
>
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>


-- 
Mike

http://twitter.com/mikekelly85
http://linkedin.com/in/mikekelly123