ZisisFl/bitcoin-P2SH-scripting

Assignment on absolute time-locked P2SH addresses using bitcoin-utils library

Project description

This project consists of two different scripts. The first one creates a P2SH Bitcoin address where all funds sent to it are locked until a specific time, specified either by block height, or UNIX Epoch time; other than the time locking the redeem script is equivalent to P2PKH. The second program spends all funds from this address.

This project is based on the bitcoin-utils Python library

Dependencies

• Python 3
• Bitcoin core node running

In order to reproduce this project it is highly recommended to create a dedicated Python 3 virtual environment

python3 -m venv bitcoin_venv
source bitcoin_venv/bin/activate
pip install -r /path/to/requirements.txt

Scripts

Script a (P2SH creator)

Script a creates (and prints in the console) a P2SH address with an absolute time lock expressed either in block height, or UNIX Epoch time

Arguments

script_a.py expects as input:

• network: the network to run this script, it can be 'regtest' or 'testnet' (is required to setup network in bitcoin-utils library)
• timelock: positive integer that refers to the specific time until when btcs sent to the P2SH addres will be locked
• private or public key: in order to create the P2SH address

Execution example

python script_a.py --network=regtest \
                   --public_key=028b7f1ea5b1a092028e653916ab66d3cb5027d950a5b5d8ee1f3d8a579f1c266c \
                   --timelock=150

Script b (P2SH spender)

Script b sends all unspent UTXOs from a P2SH address (can be one created from script a) to a P2PKH address

Arguments

script_b.py expects as input:

• network: the network to run this script, it can be 'regtest' or 'testnet' (is required to setup network in bitcoin-utils library)
• p2sh: the address created with the script_a
• private_key: the one that P2SH address belongs to
• timelock: same integer value used to create the P2SH address with script_a
• p2pkh: A P2PKH address that will receive all the UTXOs send to the P2SH (destination address)
• rpc_user: RPC user of running bitcoin node in order to init proxy
• rpc_pass: RPC password of running bitcoin node in order to init proxy

Execution example

python script_b.py --network=regtest \
                   --p2sh=2N7ZMhYhdKtvkkgR2nV6n9KaAcbgGy4tH5D \ 
                   --private_key=923zDqT2JS6ggmhWKXUsvaFnHTEFPd7XKGXQfy1FvungqDCMiLE \ 
                   --timelock=150 \
                   --p2pkh={destination_address} \ 
                   --rpc_user={rpcuser} \
                   --rpc_pass={rpcpassword}

Reproduction scenario

In order to replicate the use case scenario of these 2 scripts you can find bellow a sequence of bitcoin-cli commands used on regtest network starting at blockheight 0.

Assume your private key is 923zDqT2JS6ggmhWKXUsvaFnHTEFPd7XKGXQfy1FvungqDCMiLE
Then your public key would be 028b7f1ea5b1a092028e653916ab66d3cb5027d950a5b5d8ee1f3d8a579f1c266c

• Start a bitcoin node (regtest)

bitcoind

• Execute script a to generate a P2SH address

python script_a.py --network=regtest \
                   --public_key=028b7f1ea5b1a092028e653916ab66d3cb5027d950a5b5d8ee1f3d8a579f1c266c \
                   --timelock=150

Given the above public key and an absolute timelock of 150 blocks the following P2SH address should be creted 2N7ZMhYhdKtvkkgR2nV6n9KaAcbgGy4tH5D

• Get blockcount

bitcoin-cli getblockcount

• Create or load a wallet

bitcoin-cli createwallet "mywallet" false false "" true

or

bitcoin-cli loadwallet "mywallet"

• Get wallet info

bitcoin-cli getwalletinfo

• Create an address (sender address) and generate some bitcoins, in order to send them to the PS2H address

bitcoin-cli getnewaddress "sender_address" legacy

• List addresses of wallet

bitcoin-cli listreceivedbyaddress 1 true

• Generate blocks to the sender address (coinbase transaction)

bitcoin-cli generatetoaddress 120 {sender_address}

• Create the destination P2PKH address where we will send the UTXOs received by the P2SH address

bitcoin-cli getnewaddress "destination_address" legacy

• Check again addresses of wallet

bitcoin-cli listreceivedbyaddress 1 true

• Send bitcoin to PS2H address from the sender_address if first transaction fee rate must be set (sathoshis per vByte) (segwit transactions 1 vB = 4 bytes, else 1 vB=1 byte)

bitcoin-cli -named sendtoaddress address=2N7ZMhYhdKtvkkgR2nV6n9KaAcbgGy4tH5D amount=1 fee_rate=100

else

bitcoin-cli sendtoaddress 2N7ZMhYhdKtvkkgR2nV6n9KaAcbgGy4tH5D 1

• Check transactions in mempool

bitcoin-cli getrawmempool

Generate 1 block to complete transactions made above

bitcoin-cli generatetoaddress 1 {sender_address}

• Try spending UTXOs from P2SH to P2PKH address (this should fail as the current blockcount is < that the one set in the timelock)

python script_b.py --network=regtest \
                   --p2sh=2N7ZMhYhdKtvkkgR2nV6n9KaAcbgGy4tH5D \ 
                   --private_key=923zDqT2JS6ggmhWKXUsvaFnHTEFPd7XKGXQfy1FvungqDCMiLE \ 
                   --timelock=150 \
                   --p2pkh={destination_address} \ 
                   --rpc_user={rpcuser} \
                   --rpc_pass={rpcpassword}

• Get blockcount

bitcoin-cli getblockcount

• Generate 29 more blocks (to reach 150 blockcount)

bitcoin-cli generatetoaddress 29 {sender_address}

• Retry spending UTXOs from P2SH address by executing the script_b with same parameters

• See the details of the raw transaction

bitcoin-cli decoderawtransaction {raw transaction hex}

• Check for the transaction in the mempool

bitcoin-cli getrawmempool

Other useful bitcoin cli commands

• Check if address isvalid

bitcoin-cli validateaddress {sender_address}

• Check UTXOs that you can spend

bitcoin-cli listunspent

• Check transactions of a block

bitcoin-cli getblockhash {block count}
bitcoin-cli getblock {block hash}

• Check transaction details

bitcoin-cli gettransaction {transaction hash}

*If details category = immature the transaction was coinbase so 100 blocks have to pass until bitcoins earned can be spend