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Added simplified vault construction with CCV only
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‎examples/vault/README.md

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Compared to that prototype, this version uses the `CCV_FLAG_DEDUCT_OUTPUT_AMOUNT` to allow partial revaulting of a Vault UTXO. This was the only missing feature as compared to the implementation using `OP_VAULT` (albeit with some differences in the revaulting semantics).
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It uses the `OP_CHECKCONTRACTVERIFY` and `OP_CHECKTEMPLATEVERIFY` opcodes.
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## Prerequisites
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After following the [root prerequisites](../..#prerequisites), make sure to install the additional requirements:
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## Command-line Arguments
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- `--mine-automatically` or `-m`: Enables automatic mining any time transactions are broadcast (assuming a wallet is loaded in bitcoin-core).
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- `--script` or `-s`: Executes commands from a specified script file, instead of running the interactive CLI interface. Some examples are in the (script)[scripts] folder.
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- `--script` or `-s`: Executes commands from a specified script file, instead of running the interactive CLI interface. Some examples are in the [scripts](scripts) folder.
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## Interactive Commands
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- `withdraw`: Completes the withdrawal from the vault; will fail if the timelock of 10 blocks is not satisfied.
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The `scripts` folder has some example of interactions with the vault.
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## Minivault
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A simplified construction that only uses `OP_CHECKCONTRACTVERIFY` (without using `OP_CHECKTEMPLATEVERIFY`) is implemented in [minivault_contracts.py](minivault_contracts.py). It has all the same features of the full construction, except that the final withdrawal must necessarily go entirely to a single P2TR address.
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Check out [test_minivault.py](../../tests/test_minivault.py) to see how it would be used.

‎examples/vault/minivault_contracts.py

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from dataclasses import dataclass
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from typing import Optional
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from matt import CCV_FLAG_DEDUCT_OUTPUT_AMOUNT, NUMS_KEY
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from matt.argtypes import BytesType, IntType, SignerType
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from matt.btctools.script import OP_CHECKCONTRACTVERIFY, OP_CHECKSIG, OP_DUP, OP_PICK, OP_SWAP, OP_TRUE, CScript
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from matt.contracts import ClauseOutput, ClauseOutputAmountBehaviour, OpaqueP2TR, StandardClause, StandardP2TR, StandardAugmentedP2TR, ContractState
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from matt.script_helpers import check_input_contract, older
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class Vault(StandardP2TR):
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def __init__(self, alternate_pk: Optional[bytes], spend_delay: int, recover_pk: bytes, unvault_pk: bytes, *, has_partial_revault=True, has_early_recover=True):
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assert (alternate_pk is None or len(alternate_pk) == 32) and len(recover_pk) == 32 and len(unvault_pk)
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self.alternate_pk = alternate_pk
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self.spend_delay = spend_delay
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self.recover_pk = recover_pk
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unvaulting = Unvaulting(alternate_pk, spend_delay, recover_pk)
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self.has_partial_revault = has_partial_revault
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self.has_early_recover = has_early_recover
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# witness: <sig> <withdrawal_pk> <out_i>
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trigger = StandardClause(
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name="trigger",
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script=CScript([
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# data and index already on the stack
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0 if alternate_pk is None else alternate_pk, # pk
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unvaulting.get_taptree_merkle_root(), # taptree
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0, # standard flags
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OP_CHECKCONTRACTVERIFY,
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unvault_pk,
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OP_CHECKSIG
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]),
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arg_specs=[
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('sig', SignerType(unvault_pk)),
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('withdrawal_pk', BytesType()),
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('out_i', IntType()),
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],
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next_outputs_fn=lambda args, _: [ClauseOutput(
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n=args['out_i'],
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next_contract=unvaulting,
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next_state=unvaulting.State(withdrawal_pk=args["withdrawal_pk"])
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)]
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)
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# witness: <sig> <withdrawal_pk> <trigger_out_i> <revault_out_i>
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trigger_and_revault = StandardClause(
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name="trigger_and_revault",
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script=CScript([
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0, OP_SWAP, # no data tweak
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# <revault_out_i> from the witness
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-1, # current input's internal key
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-1, # current input's taptweak
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CCV_FLAG_DEDUCT_OUTPUT_AMOUNT, # revault output
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OP_CHECKCONTRACTVERIFY,
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# data and index already on the stack
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0 if alternate_pk is None else alternate_pk, # pk
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unvaulting.get_taptree_merkle_root(), # taptree
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0, # standard flags
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OP_CHECKCONTRACTVERIFY,
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unvault_pk,
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OP_CHECKSIG
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]),
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arg_specs=[
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('sig', SignerType(unvault_pk)),
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('withdrawal_pk', BytesType()),
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('out_i', IntType()),
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('revault_out_i', IntType()),
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],
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next_outputs_fn=lambda args, _: [
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ClauseOutput(n=args['revault_out_i'], next_contract=self,
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next_amount=ClauseOutputAmountBehaviour.DEDUCT_OUTPUT),
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ClauseOutput(
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n=args['out_i'],
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next_contract=unvaulting,
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next_state=unvaulting.State(withdrawal_pk=args["withdrawal_pk"])),
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]
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)
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# witness: <out_i>
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recover = StandardClause(
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name="recover",
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script=CScript([
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0, # data
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OP_SWAP, # <out_i> (from witness)
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recover_pk, # pk
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0, # taptree
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0, # flags
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OP_CHECKCONTRACTVERIFY,
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OP_TRUE
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]),
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arg_specs=[
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('out_i', IntType()),
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],
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next_outputs_fn=lambda args, _: [ClauseOutput(n=args['out_i'], next_contract=OpaqueP2TR(recover_pk))]
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)
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if self.has_partial_revault:
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if self.has_early_recover:
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clauses = [trigger, [trigger_and_revault, recover]]
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else:
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clauses = [trigger, trigger_and_revault]
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else:
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if self.has_early_recover:
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clauses = [trigger, recover]
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else:
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clauses = trigger
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super().__init__(NUMS_KEY if alternate_pk is None else alternate_pk, clauses)
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class Unvaulting(StandardAugmentedP2TR):
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@dataclass
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class State(ContractState):
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withdrawal_pk: bytes
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def encode(self):
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return self.withdrawal_pk
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def encoder_script():
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return CScript([])
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def __init__(self, alternate_pk: Optional[bytes], spend_delay: int, recover_pk: bytes):
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assert (alternate_pk is None or len(alternate_pk) == 32) and len(recover_pk) == 32
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self.alternate_pk = alternate_pk
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self.spend_delay = spend_delay
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self.recover_pk = recover_pk
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# witness: <withdrawal_pk>
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withdrawal = StandardClause(
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name="withdraw",
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script=CScript([
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OP_DUP,
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*check_input_contract(-1, alternate_pk),
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# Check timelock
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*older(self.spend_delay),
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# Check that the transaction output is as expected
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0, # no data
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0, # output index
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2, OP_PICK, # withdrawal_pk
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0, # no taptweak
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0, # default flags
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OP_CHECKCONTRACTVERIFY,
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# withdrawal_pk is left on the stack on success
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]),
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arg_specs=[
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('withdrawal_pk', BytesType())
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],
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next_outputs_fn=lambda args, _: [ClauseOutput(n=0, next_contract=OpaqueP2TR(args['withdrawal_pk']))]
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)
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# witness: <out_i>
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recover = StandardClause(
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name="recover",
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script=CScript([
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0, # data
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OP_SWAP, # <out_i> (from witness)
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recover_pk, # pk
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0, # taptree
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0, # flags
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OP_CHECKCONTRACTVERIFY,
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OP_TRUE
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]),
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arg_specs=[
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('out_i', IntType()),
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],
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next_outputs_fn=lambda args, _: [ClauseOutput(n=args['out_i'], next_contract=OpaqueP2TR(recover_pk))]
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)
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super().__init__(NUMS_KEY if alternate_pk is None else alternate_pk, [withdrawal, recover])

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