📅 Original date posted:2019-12-02
📝 Original message:
Conner Fromknecht <conner at lightning.engineering> writes:
> Hi all,
>
> I recently revisited the eltoo paper and noticed some things related
> watchtowers that might affect channel construction.
>
> Due to NOINPUT, any update transaction _can_ spend from any other, so
> in theory the tower only needs the most recent update txn to resolve
> any dispute.
>
> In order to spend, however, the tower must also produce a witness
> script which when hashed matches the witness program of the input. To
> ensure settlement txns can only spend from exactly one update txn,
> each update txn uses unique keys for the settlement clause, meaning
> that each state has a _unique_ witness program.
I didn't think this was the design. The update transaction can spend
any prior, with a fixed script, due to NOINPUT.
The settlement transaction does *not* use NOINPUT, and thus can only
spend the matching update.
Cheers,
Rusty.
Rusty Russell [ARCHIVE] /
npub1zw…hkhpx
2023-06-09 12:57:32
in reply to nevent1q…zyr3
Author Public Key
npub1zw7cc8z78v6s3grujfvcv3ckpvg6kr0w7nz9yzvwyglyg0qu5sjsqhkhpxPublished at
2023-06-09 12:57:32Event JSON
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"content": "📅 Original date posted:2019-12-02\n📝 Original message:\nConner Fromknecht \u003cconner at lightning.engineering\u003e writes:\n\u003e Hi all,\n\u003e\n\u003e I recently revisited the eltoo paper and noticed some things related\n\u003e watchtowers that might affect channel construction.\n\u003e\n\u003e Due to NOINPUT, any update transaction _can_ spend from any other, so\n\u003e in theory the tower only needs the most recent update txn to resolve\n\u003e any dispute.\n\u003e\n\u003e In order to spend, however, the tower must also produce a witness\n\u003e script which when hashed matches the witness program of the input. To\n\u003e ensure settlement txns can only spend from exactly one update txn,\n\u003e each update txn uses unique keys for the settlement clause, meaning\n\u003e that each state has a _unique_ witness program.\n\nI didn't think this was the design. The update transaction can spend\nany prior, with a fixed script, due to NOINPUT.\n\nThe settlement transaction does *not* use NOINPUT, and thus can only\nspend the matching update.\n\nCheers,\nRusty.",
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