[psbt saga part 4/4]: Multisig demo

[guggero]

Depends on #787.

This PR adds an integration test that demonstrates how multi signatures can be used on both the BTC and asset level.
In the demo we use the following Tapscript to encumber the BTC level anchor output:

<key_1> OP_CHECKSIG <key_2> OP_CHECKSIGADD 2 OP_EQUAL

This is basically a 2-of-2 multi signature. To make sure the key spend path cannot be taken, we use the NUMS public key as the internal key.

On the asset level, we use a script key that is the MuSig2 combined key of two script keys.

This means that the 1000 units of assets sent to the constructed TAP address will be co-owned by both tapd instances, on the asset and BTC level.

We then spend from that address again, just to demonstrate how the witnesses for such transfers would be created.

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This change is 

[Roasbeef]

🌙

Reviewed 1 of 1 files at r1, 1 of 1 files at r2, 1 of 1 files at r3, 10 of 10 files at r4, 11 of 11 files at r5, all commit messages.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @GeorgeTsagk and @guggero)

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tapdb/sqlc/queries/assets.sql line 296 at r4 (raw file):

WHERE spent = FALSE
GROUP BY assets.genesis_id, genesis_info_view.asset_id,
         version, genesis_info_view.asset_tag, genesis_info_view.meta_hash,

Hmm, trying to remember why we also wanted to group by version in the first place 🤔

[GeorgeTsagk]

Looks good! 👌

[lukegao209]

Hi @guggero I saw the video about Multisig.
I have one question : Alice (tapd) + Bob(tapd) + Third party(tapd) Multisig.

for David(no tapd with) :

1. is it possible for alice to send an asset to Bob,and the target is multisig by (Bob,David,Third Party)?
2. can David and Bob transfer the asset by their Multisig?

[guggero]

1. is it possible for alice to send an asset to Bob,and the target is multisig by (Bob,David,Third Party)?

Yes, definitely. Both on the BTC level (internal_key and tapscript_sibling of the NewAddrRequest message) as well as on the asset level (custom script_key). Of course Alice would need to know all the public keys involved, so she can construct the outputs. Alice would then send the proof to Bob as usual and Bob can import it to show the asset in ListAssets. I think the only caveat is that the script_key_is_local field in the ListAssets response would be false, because the tadp wallet wouldn't be able to spend the asset without externally produced signatures.

2. can David and Bob transfer the asset by their Multisig?

Yes, if they use the correct RPCs to create the correct signatures.

[lukegao209]

1. is it possible for alice to send an asset to Bob,and the target is multisig by (Bob,David,Third Party)?

Yes, definitely. Both on the BTC level (internal_key and tapscript_sibling of the NewAddrRequest message) as well as on the asset level (custom script_key). Of course Alice would need to know all the public keys involved, so she can construct the outputs. Alice would then send the proof to Bob as usual and Bob can import it to show the asset in ListAssets. I think the only caveat is that the script_key_is_local field in the ListAssets response would be false, because the tadp wallet wouldn't be able to spend the asset without externally produced signatures.

2. can David and Bob transfer the asset by their Multisig?

Yes, if they use the correct RPCs to create the correct signatures.

Its a great feature. its possible for btccoin address to receive taproot assets without tapd.