Signing Custom Tapscript Leaves with walletprocesspsbt using Bitcoind
As a taproot-wallet user, you’re likely familiar with the complexity of handling multisig scripts in Bitcoin. In this article, we’ll explore how to sign custom tapscript leaves using the walletprocesspsbt RPC endpoint from within a Bitcoin node.
Understanding Multisig Scripts and Tapscripts
Multisig scripts are used in taproot wallets to enable multiple parties to spend funds without revealing their private keys. Each multisig script is defined as a tapscript, which is a sequence of transactions that specify how to spend the funds. In your case, you have three different script paths for each multisig.
Tapscripts can be compiled and optimized by Bitcoin Core (the default wallet software) into scripts that can be used to sign custom leaves. A “leaf” in this context refers to a single transaction output that’s part of a multisig script.
Walletprocesspsbt RPC Endpoint
The walletprocesspsbt endpoint is a powerful tool provided by Bitcoind, the official Bitcoin node software. It allows you to process payment requests and generate multiple transaction outputs from your wallet’s private keys. You can use this endpoint to sign custom leaves using tapscripts.
To get started, make sure you have Bitcoin Core installed on your system and running. Then, navigate to your wallet’s configuration directory:
cd ~/.bitcoincorewallet
Next, edit the settings.conf file (usually located at ~/.bitcoincorewallet/settings.conf) to add the following line:
rpc-process-pssbt = true
This tells Bitcoin Core to use the walletprocesspsbt endpoint.
Signing Custom Leaves with Tapscripts
Now that you’ve enabled the walletprocesspsbt endpoint, you can sign custom leaves using tapscripts. Here’s an example of how to compile a tapscript for multisig script path 1:
taproot-compile -scriptpath /path/to/script1.txb --outputpath /path/to/output1.p2sh
Replace /path/to/script1.txb with the actual file containing your multisig script, and /path/to/output1.p2sh with the desired output file format (e.g., p2sh).
Once you’ve compiled the tapscript, you can use the walletprocesspsbt endpoint to sign it using your private key:
bitcoincorewallet --rpc-process-pssbt p2sh --path /path/to/output1.p2sh --privatekey
This will generate a single transaction output that contains all the multisig script outputs.
Example Use Case
Suppose you have three different multisig scripts defined as tapscripts, and each has a different script path. You can compile them using taproot-compile and then use the walletprocesspsbt endpoint to sign custom leaves for each script:
Compile multisig scripts 1-3
taproot-compile -scriptpath /path/to/script1.txb --outputpath /path/to/output1.p2sh
taproot-compile -scriptpath /path/to/script2.txb --outputpath /path/to/output2.p2sh
taproot-compile -scriptpath /path/to/script3.txb --outputpath /path/to/output3.p2sh
Sign custom leaves for each multisig script
bitcoincorewallet --rpc-process-pssbt p2sh --path /path/to/output1.p2sh --privatekey \
--scriptpath /path/to/script1.txb \
--script 0x1234567890abcdef \
--output /path/to/output1
This will generate three custom transaction outputs that contain all the multisig script outputs for each script.
In summary, you can sign custom tapscripts using walletprocesspsbt and generate multiple transaction outputs from your wallet’s private keys. This allows you to handle complex multisig scripts in taproot wallets with ease.