[Lightning-dev] eltoo implementation in Bitcoin functional test framework

[Antoine Riard]

Hello all,

Didn't listen to Pieter Wuille interview, so don't know how he was thinking
to use miniscript for lightning.
But currently in lightning all our scripts are templates, a use of a
miniscript compiler would be to find optimized bitcoin scripts for a given
policy which model the channel and then hardcode them in lightning backend.
The other use I can see would be to use miniscript to write customizable
conditional-payment than our basic HTLCs, real hurdle would be to implement
on-chain monitoring and resolution right.
Not sure how Eltoo fit into it as it's a sighash extension to get a new
update mechanism, miniscript seems more tailored for the transfer layer.

Regards,
Antoine

Le mer. 4 sept. 2019 à 08:53, Bastien TEINTURIER <bastien at acinq.fr> a
écrit :

> Good morning Richard,
>
> This is an interesting initiative, I'm curious to see the results!
> I know we haven't worked on any Eltoo implementation yet at Acinq and I
> don't know if others have attempted it.
>
> However I have a very open question that may impact your project.
> I'm starting to look at miniscript [1] (still a total noob though) and
> listened to an interview where Pieter Wuille briefly mentioned that using
> miniscript for lightning may be more future-proof and extensible than
> directly using bitcoin script.
> Have you considered first re-writing the Eltoo scripts with miniscript? Or
> did someone else on this list attempt this already?
> Do people on this list have opinions on whether that is the right
> direction for Eltoo scripts (and maybe even for Bolt 1.x scripts if
> *any_prevout* never makes it to Bitcoin scripts)?
>
> Cheers,
> Bastien
>
> [1] http://bitcoin.sipa.be/miniscript/
>
> Le mer. 4 sept. 2019 à 13:20, Richard Myers <rich at gotenna.com> a écrit :
>
>> Hi All,
>>
>> To better understand how the eltoo update scheme (
>> https://blockstream.com/eltoo.pdf ) works in practice I implemented
>> eltoo in the Bitcoin functional test framework. These simulations exercise
>> a concrete implementation of the eltoo Bitcoin scripts and explore the data
>> flow between nodes that use eltoo to update their channel state.
>>
>> My motivation for creating these tests is to have a framework for both
>> understanding and refining the Bitcoin scripts and message passing protocol
>> for eltoo. I’d love to hear what people think of my initial implementation.
>>
>> This simulation uses a fork of Bitcoin with cdecker’s SIGHASH_NOINPUT
>> patch applied to the signet2 fork fjahr created with patches applied for
>> signet (kallewoof), taproot (sipa) and anyprevout* (ajtowns).
>>
>>
>> https://github.com/remyers/signet2/blob/eltoo/test/functional/simulate_eltoo.py
>>
>> Next steps:
>>
>>    -
>>
>>    add bidirectional channel updates
>>    -
>>
>>    derive public keys for settle transactions from a pre-shared basepoint
>>
>>
>> Does anyone know of any other eltoo implementations? I’d love to compare
>> notes and get the ball rolling on a detailed specification.
>>
>> Special thanks to the Chaincode Summer Residency and Christian Decker for
>> their helpful advice and encouragement while I worked on this project.
>>
>>   -- Richard
>>
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>>
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