Subject: Re: [bitcoin-dev] Playing with full-rbf peers for fun and L2s security

From: Peter Todd <[email-masked]>
Date: Sun, 26 Jun 2022 20:43:35 -0400

On Sun, Jun 26, 2022 at 04:40:24PM +0000, alicexbt via bitcoin-dev wrote:
> Hi Antoine,
> 
> Thanks for sharing the DoS attack example with alternatives.
> 
> > - Caroll broadcasts a double-spend of her own input C, the double-spend is attached with a low-fee (1sat/vb) and it does _not_ signal opt-in RBF
> > - Alice broadcasts the multi-party transaction, it is rejected by the network mempools because Alice double-spend is already present
> 
> I think this affects almost all types of coinjoin transaction including coordinator based implementations. I tried a few things and have already reported details for an example DoS attack to one of the team but there is no response yet.
> 
> It was fun playing with RBF, DoS and Coinjoin. Affected projects should share their opinion about full-rbf as it seems it might improve things.
> 
> Example:
> 
> In Wasabi an attacker can broadcast a transaction spending input used in coinjoin after sending signature in the round. This would result in a coinjoin tx which never gets relayed: https://nitter.net/1440000bytes/status/1540727534093905920

Note that Wasabi already has a DoS attack vector in that a participant can stop
participating after the first phase of the round, with the result that the
coinjoin fails. Wasabi mitigates that by punishing participating in future
rounds. Double-spends only create additional types of DoS attack that need to
be detected and punished as well - they don't create a fundamentally new
vulerability.

-- 
https://petertodd.org 'peter'[:-1]@petertodd.org