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Date: Fri, 20 Oct 2023 11:03:43 +0000
From: Peter Todd <pete@petertodd.org>
To: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Message-ID: <ZTJej/ipIl5hZIUn@petertodd.org>
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Cc: security@ariard.me,
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 <lightning-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] [Lightning-dev] Full Disclosure: CVE-2023-40231 /
 CVE-2023-40232 / CVE-2023-40233 / CVE-2023-40234 "All your mempool are
 belong to us"
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On Fri, Oct 20, 2023 at 10:31:03AM +0000, Peter Todd via bitcoin-dev wrote:
> As I have suggested before, the correct way to do pre-signed transactions=
 is to
> pre-sign enough *different* transactions to cover all reasonable needs for
> bumping fees. Even if you just increase the fee by 2x each time, pre-sign=
ing 10
> different replacement transactions covers a fee range of 1024x. And you
> obviously can improve on this by increasing the multiplier towards the en=
d of
> the range.

To be clear, when I say "increasing the multiplier", I mean, starting with a
smaller multiplier at the beginning of the range, and ending with a bigger =
one.

Eg feebumping with fee increases pre-signed for something like:

    1.1
    1.2
    1.4
    1.8
    2.6
    4.2
    7.4

etc.

That would use most of the range for smaller bumps, as a %, with larger % b=
umps
reserved for the end where our strategy is changing to something more
"scorched-earth"

And of course, applying this idea properly to commitment transactions will =
mean
that the replacements may have HTLCs removed, when their value drops below =
the
fees necessary to get those outputs mined.

Note too that we can sign simultaneous variants of transactions that deduct=
 the
fees from different party's outputs. Eg Alice can give Bob the ability to
broadcast higher and higher fee txs, taking the fees from Bob's output(s), =
and
Bob can give Alice the same ability, taking the fees from Alice's output(s)=
=2E I
haven't thought through how this would work with musig. But you can certain=
ly
do that with plain old OP_CheckMultisig.

--=20
https://petertodd.org 'peter'[:-1]@petertodd.org

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