Taproot multisig sample

examples/src/main/kotlin/MultisigTaprootTransaction.kt

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+package org.bitcoindevkit
+
+fun main() {
+    // Add your regtest URL here. Regtest environment must have esplora to run this.
+    // See here for regtest podman setup https://github.com/thunderbiscuit/podman-regtest-infinity-pro
+    val REGTEST_URL = "http://127.0.0.1:3002"
+
+    // An unspendable compressed public key to use as internal key for Taproot multisig
+    // This could be any valid compressed public key that no one has the private key for or
+    // full descriptor path including derivation.
+    val UNSPENDABLE_KEY = "0250929b74c1a04954b78b4b6035e97a5e078a5a0f28ec96d547bfee9ace803ac0"
+
+    // Create 3 wallets using existing helper (P2TR = Taproot)
+    val aliceWallet = getNewWallet(ActiveWalletScriptType.P2TR, Network.REGTEST)
+    val bobWallet = getNewWallet(ActiveWalletScriptType.P2TR, Network.REGTEST)
+    val mattWallet = getNewWallet(ActiveWalletScriptType.P2TR, Network.REGTEST)
+
+    // Get the public descriptors of each wallet. Extract inner key expressions
+    var alicePublicDescriptor = aliceWallet.publicDescriptor(KeychainKind.EXTERNAL)
+    alicePublicDescriptor = alicePublicDescriptor.substring(alicePublicDescriptor.indexOf("(") + 1, alicePublicDescriptor.indexOf(")"))
+    var bobPublicDescriptor = bobWallet.publicDescriptor(KeychainKind.EXTERNAL)
+    bobPublicDescriptor = bobPublicDescriptor.substring(bobPublicDescriptor.indexOf("(") + 1, bobPublicDescriptor.indexOf(")"))
+    var mattPublicDescriptor = mattWallet.publicDescriptor(KeychainKind.EXTERNAL)
+    mattPublicDescriptor = mattPublicDescriptor.substring(mattPublicDescriptor.indexOf("(") + 1, mattPublicDescriptor.indexOf(")"))
+
+    // Get the change descriptors of each wallet (for change path)
+    var aliceChangeDescriptor = aliceWallet.publicDescriptor(KeychainKind.INTERNAL)
+    aliceChangeDescriptor = aliceChangeDescriptor.substring(aliceChangeDescriptor.indexOf("(") + 1, aliceChangeDescriptor.indexOf(")"))
+    var bobChangeDescriptor = bobWallet.publicDescriptor(KeychainKind.INTERNAL)
+    bobChangeDescriptor = bobChangeDescriptor.substring(bobChangeDescriptor.indexOf("(") + 1, bobChangeDescriptor.indexOf(")"))
+    var mattChangeDescriptor = mattWallet.publicDescriptor(KeychainKind.INTERNAL)
+    mattChangeDescriptor = mattChangeDescriptor.substring(mattChangeDescriptor.indexOf("(") + 1, mattChangeDescriptor.indexOf(")"))
+
+    // Define Taproot multisig descriptors. For Taproot, an internal key is required.
+    // We use a random unspendable compressed public key as the internal key. This means
+    // that the wallet can only be spent via the script path (no key-path spending).
+    val externalDescriptor = Descriptor(
+        descriptor = "tr($UNSPENDABLE_KEY,multi_a(2,$alicePublicDescriptor,$bobPublicDescriptor,$mattPublicDescriptor))",
+        network = Network.REGTEST
+    )
+    val changeDescriptor = Descriptor(
+        descriptor = "tr($UNSPENDABLE_KEY,multi_a(2,$aliceChangeDescriptor,$bobChangeDescriptor,$mattChangeDescriptor))",
+        network = Network.REGTEST
+    )
+
+    // Create multisig wallet (reuse shared persistence helper)
+    val connection: Persister = Persister.newSqlite(generateUniquePersistenceFilePath())
+    val multisigWallet = Wallet(externalDescriptor, changeDescriptor, Network.REGTEST, connection)
+
+    val changeAddress = multisigWallet.revealNextAddress(KeychainKind.INTERNAL)
+    val address = multisigWallet.revealNextAddress(KeychainKind.EXTERNAL)
+    println("Change address: ${changeAddress.address}")
+
+    // Fund this address. Alice, Bob and Matt own funds sent here
+    println("receiving address: ${address.address}")
+
+    // Client: wait for funding then scan
+    println("Waiting 40 seconds for funds to arrive here before scanning ${address.address} ...")
+    Thread.sleep(40000)
+
+    val esploraClient = EsploraClient(REGTEST_URL)
+    val fullScanRequest: FullScanRequest = multisigWallet.startFullScan().build()
+    val update = esploraClient.fullScan(fullScanRequest, 10uL, 1uL)
+    multisigWallet.applyUpdate(update)
+    multisigWallet.persist(connection)
+    println("Balance: ${multisigWallet.balance().total.toSat()}")
+
+    Thread.sleep(40000)
+
+    // Create PSBT
+    val recipient = Address("bcrt1q645m0j78v9pajdfp0g0w6wacl4v8s7mvrwsjx5", Network.REGTEST)
+    println("Balance: ${multisigWallet.balance().total.toSat()}")
+    val psbt: Psbt = TxBuilder()
+        .addRecipient(recipient.scriptPubkey(), Amount.fromSat(4420uL))
+        .feeRate(FeeRate.fromSatPerVb(22uL))
+        .finish(multisigWallet)
+
+    val psbtTransaction = psbt.extractTx()
+    println(psbtTransaction.toString())
+    println("Before any signature ${psbt.serialize()}")
+    println("Before any signature. Json: ${psbt.jsonSerialize()}")
+
+    // Sign Psbt via script path; do not allow key-path signing so taptree fields are populated
+    aliceWallet.sign(psbt, SignOptions(
+        trustWitnessUtxo = false,
+        assumeHeight = null,
+        allowAllSighashes = false,
+        tryFinalize = false,
+        signWithTapInternalKey = false,
+        allowGrinding = false
+    ))
+    println("After signing with aliceWallet ${psbt.serialize()}")
+    println("After signing with aliceWallet Json ${psbt.jsonSerialize()}")
+    println("Transaction after signing with wallet1: ${psbt.extractTx().toString()}")
+
+    bobWallet.sign(psbt, SignOptions(
+        trustWitnessUtxo = false,
+        assumeHeight = null,
+        allowAllSighashes = false,
+        tryFinalize = false,
+        signWithTapInternalKey = false,
+        allowGrinding = false
+    ))
+    println("After signing with bobWallet ${psbt.serialize()}")
+    println("After signing with bobWallet Json ${psbt.jsonSerialize()}")
+    println("Transaction after signing with bobWallet: ${psbt.extractTx().toString()}")
+
+    // Matt does not need to sign since it is a 2 of 3 multisig. Alice and Bob have already signed.
+    mattWallet.sign(psbt, SignOptions(
+        trustWitnessUtxo = false,
+        assumeHeight = null,
+        allowAllSighashes = false,
+        tryFinalize = false,
+        signWithTapInternalKey = false,
+        allowGrinding = false
+    ))
+    println("After signing with mattWallet ${psbt.serialize()}")
+    println("After signing with mattWallet Json ${psbt.jsonSerialize()}")
+    println("Transaction after signing with mattWallet: ${psbt.extractTx().toString()}")
+
+    multisigWallet.finalizePsbt(psbt)
+    println("After finalize: ${psbt.serialize()}")
+    println("After finalize Json: ${psbt.jsonSerialize()}")
+    println("Transaction after finalize: ${psbt.extractTx().toString()}")
+
+
+    val tx: Transaction = psbt.extractTx()
+    println("Txid is: ${tx.computeTxid()}")
+
+    // Now you can broadcast the transaction
+    esploraClient.broadcast(tx)
+    println("Tx was broadcasted")
+}