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Date: Thu, 10 Nov 2022 17:00:58 -1000
From: "David A. Harding" <dave@dtrt.org>
To: Peter Todd <pete@petertodd.org>, Bitcoin Protocol Discussion
 <bitcoin-dev@lists.linuxfoundation.org>
In-Reply-To: <Y2l1/qXHxyctU9ir@petertodd.org>
References: <Y2ln2fJ+8+Q0qS0E@petertodd.org> <Y2l1/qXHxyctU9ir@petertodd.org>
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Subject: Re: [bitcoin-dev] Using Full-RBF to fix BIP-125 Rule #3 Pinning
 with nLockTime
Precedence: list

On 2022-11-07 11:17, Peter Todd via bitcoin-dev wrote:
> We can ensure with high probability that the transaction can be 
> cancelled/mined
> at some point after N blocks by pre-signing a transaction, with 
> nLockTime set
> sufficiently far into the future, spending one or more inputs of the
> transaction with a sufficiently high fee that it would replace 
> transaction(s)
> attempting to exploit Rule #3 pinning (note how the package limits in 
> Bitcoin
> Core help here).

This implies a floor on the funds involved in a contract.  For example, 
if the pinning transaction is 100,000 vbytes at a feerate of 1 sat/vb, 
the minimum contract amount must be a bit over 100,000 sats (about $17 
USD at current prices).  However, participants in a contract not meant 
to settle immediately probably need to assume the worst case future 
pinning, for example where transactions paying even 100 sat/vb won't be 
mined promptly; in which case the minimum contract amount becomes 
something like $1,700 USD.

That seems sub-optimal to me.

-Dave