Subject: Re: [bitcoindev] Anyone can boost - a more efficient alternative to anchor outputs

From: Peter Todd <[email-masked]>
Date: Wed, 27 Mar 2024 12:20:54 +0000

On Sun, Mar 24, 2024 at 03:36:30PM -1000, David A. Harding wrote:
> On 2024-03-19 04:24, Peter Todd wrote:
> > To reduce trust you could do an automated, multiple round, signing
> > scheme where
> > the service signs transations with higher and higher fee-rates in
> > exchange for
> > most funds over LN.
> 
> When the service thinks the user has paid all that they're going to pay,
> what stops them from replacing their transaction one more time with a
> version that does not sponsor the user's transaction?

That at least is mitigated a bit by the fact that the earlier versions existed
and were valid; it's still a potentially useful reduction in trust as the
service needs to be able to do something economically useful with the high-fee
transaction for it to be a profitable attack.

As I said, I'm suggesting a way to reduce trust. Not eliminate it.

> Also, what stops the
> service from selling the same space in a sponsor transaction to multiple
> users at once, e.g. customers Alice and Bob each iterate with the service
> many times until they get a sponsor with as much fee as they want, but when
> they go to broadcast, they discover that their transactions conflict, so one
> of them paid for nothing?

That might actually be a weaker attack than the first: you can watch a mempool,
unknown to the service, to see if you recieve the transaction you paid for. If
you don't, there's a reasonable chance they're trying to rip you off.

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

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