<p>You are right. You could either use a leaf with a single aggregated key or a leaf with a more traditional multisig construction using <code>OP_CHECKSIGADD</code>.</p>
<p>The advantage of the aggregated key is its smaller input saving fees. The disadvantage is that MuSig2 is an interactive protocol with multiple rounds which can be inconvenient if some of the signers are airgapped systems.</p>
<p>The <code>OP_CHECKSIGADD</code> construction on the other hand is a non-interactive construction, but reveals more information on-chain and costs more.</p>

CC BY-SA 4.0
2021-06-23T15:09:51.257Z
2021-10-28T17:18:38.330Z
2021-10-28T17:18:38.330Z
Murch
<p>I know that it is possible to create a 2-2 multsig using Taproot by combining both private keys into one public key and defining that as the key path spend. I also know that it is possible to use Tapscript to do the same thing with a script path spend using OP_CHECKSIGADD.</p>
<p>Is it also possible to use key aggregation in the script path spend, by just providing a public key and signature but doing the same key aggregation as in the key path spend? If so, would it ever make sense to use a &quot;normal&quot; OP_CHECKSIGADD operation in the case of multisig (not threshold signatures).</p>

<cryptography><taproot><musig><p2tr><key-aggregation>
Using key aggregation (multsig) in P2TR script path spends
Hellwerker
# Using key aggregation (multsig) in P2TR script path spends

(Asked by: username_0 on 2021-04-04)

I know that it is possible to create a 2-2 multsig using Taproot by combining both private keys into one public key and defining that as the key path spend. I also know that it is possible to use Tapscript to do the same thing with a script path spend using OP\_CHECKSIGADD.

Is it also possible to use key aggregation in the script path spend, by just providing a public key and signature but doing the same key aggregation as in the key path spend? If so, would it ever make sense to use a "normal" OP\_CHECKSIGADD operation in the case of multisig (not threshold signatures).

**Tags:** cryptography, taproot, musig, p2tr, key-aggregation


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## 1 answers

### Answer by username_1 on 2021-06-23. Score: 2 | Accepted answer

You are right. You could either use a leaf with a single aggregated key or a leaf with a more traditional multisig construction using `OP_CHECKSIGADD`.

The advantage of the aggregated key is its smaller input saving fees. The disadvantage is that MuSig2 is an interactive protocol with multiple rounds which can be inconvenient if some of the signers are airgapped systems.

The `OP_CHECKSIGADD` construction on the other hand is a non-interactive construction, but reveals more information on-chain and costs more.


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