Re: [bitcoin-dev] Standardisation of an unstructured taproot annex

2023-06-15 Thread Joost Jager via bitcoin-dev
Hi Greg,

Getting back to this:

Another solution could be to make annex usage "opt-in"
> by requiring all inputs to commit to an annex to be relay-standard. In
> this case, you've opted into a possible
> vector, but at least current usage patterns wouldn't be unduly affected.
>

Ignoring the argument that policy may provide a false sense of security, I
think this is an interesting idea. Opt-in would enable convenants through
presigned txes with atomic on-chain signature backup, without needing to
worry about non-annex multi-party protocols (coinjoin and dual funded
lightning mentioned previously) that may suffer from annex inflation or the
last signer presenting an unexpected annex. The downside is just that extra
empty annex byte per input, if there are other inputs involved. To me that
would be a reasonable trade-off.

Would it then still be necessary to restrict the annex to a maximum size?
Perhaps not opting into annex for multi-party protocols is sufficient. Or
otherwise, #24007 may be helpful. It is hard to pick a constant usually.

Joost.
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Re: [bitcoin-dev] Standardisation of an unstructured taproot annex

2023-06-15 Thread Greg Sanders via bitcoin-dev
Hi Joost,

> Ignoring the argument that policy may provide a false sense of security

This may take longer form arguments than I'm willing to make on this
thread, but I think this only true in a shallower sense that we cannot know
for sure that anything will be confirmed quickly. When crafting policy, we
are trying to make as reliable-as-possible systems to allow people to pay
miners. That may mean opening up the annex to potential use-cases, but it
certainly means allowing current users of the p2p network to make
reasonable feerate transactions in coinjoin-like scenarios. Ideally we
shoot for as many use cases as we can, to pay these miners.

> Would it then still be necessary to restrict the annex to a maximum size?

I think it's worth thinking about to protect the opt-in users, and can also
be used for other anti-pinning efforts(though clearly not sufficient by
itself for the many many pinning vectors we have :) )

Cheers,
Greg

On Thu, Jun 15, 2023 at 5:36 AM Joost Jager  wrote:

> Hi Greg,
>
> Getting back to this:
>
> Another solution could be to make annex usage "opt-in"
>> by requiring all inputs to commit to an annex to be relay-standard. In
>> this case, you've opted into a possible
>> vector, but at least current usage patterns wouldn't be unduly affected.
>>
>
> Ignoring the argument that policy may provide a false sense of security, I
> think this is an interesting idea. Opt-in would enable convenants through
> presigned txes with atomic on-chain signature backup, without needing to
> worry about non-annex multi-party protocols (coinjoin and dual funded
> lightning mentioned previously) that may suffer from annex inflation or the
> last signer presenting an unexpected annex. The downside is just that extra
> empty annex byte per input, if there are other inputs involved. To me that
> would be a reasonable trade-off.
>
> Would it then still be necessary to restrict the annex to a maximum size?
> Perhaps not opting into annex for multi-party protocols is sufficient. Or
> otherwise, #24007 may be helpful. It is hard to pick a constant usually.
>
> Joost.
>
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