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Charms

Enchanting a transaction

Now that we have implemented an app, we’re ready to put a spell onto a real Bitcoin transaction. This guide is pretty low level, as we’re using bitcoin-cli to interact with the Bitcoin network.

Pre-requisites

Bitcoin Core v22.0 or later is required:

Terminal window
brew install bitcoin

This walkthrough assumes a bitcoin node running with the following configuration (bitcoin.conf):

server=1
testnet4=1
txindex=1
addresstype=bech32m
changetype=bech32m

On macOS, bitcoin.conf is usually located at ~/Library/Application Support/Bitcoin/bitcoin.conf.

You will need to have bitcoin-cli aliased as b:

Terminal window
alias b=bitcoin-cli

You will also need to have jq installed:

Terminal window
brew install jq

Walkthrough

Terminal window
recipient="$(b getnewaddress)"


rawtxhex=$(b createrawtransaction '''[]''' '''[{ "'$recipient'": 0.00010000 }]''')


# or something like this if you want to spend an existing Charm
# rawtxhex=$(b createrawtransaction '''[ { "txid": "dafd94568e0d8fb0e72c9bb84e54b227c9cad28168611fe3d37f06276125e247", "vout": 0 } ]''' '''[{ "'$recipient'": 0.00010000 }]''')


fee_rate=2 # per vB


draft_tx_hex=$(b -named fundrawtransaction $rawtxhex changePosition=1 fee_rate=$fee_rate | jq -r '.hex')


# now choose a funding output with a few thousand sats (10000 should be more than enough)
b listunspent


# MUST NOT be one of those being spent by $draft_tx_hex (printed out by this)
b decoderawtransaction $(echo $draft_tx_hex) | jq -r '.vin[] | "\(.txid):\(.vout)"'


funding_utxo_id=acbef6b2f3808ad4fe36fff4d70ba1d0ccc05ce254d8096a8591de76683af8d0:0
funding_utxo_value=10000
# value in sats


change_address=$(b getrawchangeaddress)


b decoderawtransaction $draft_tx_hex


# now get the hex representation of $draft_tx_hex's input transactions


prev_txs=$(b decoderawtransaction $draft_tx_hex | jq -r '.vin[].txid' | sort | uniq | xargs -I {} bitcoin-cli getrawtransaction {} | paste -sd, -)


spell_source=./examples/toad-token/spells/mint-token.yml
toad_app_bin=./examples/toad-token/elf/riscv32im-succinct-zkvm-elf


RUST_LOG=info charms spell prove --spell=$spell_source --tx=$draft_tx_hex --prev-txs=$prev_txs --app-bins=$toad_app_bin --funding-utxo-id=$funding_utxo_id --funding-utxo-value=$funding_utxo_value --change-address=$change_address --fee-rate=$fee_rate


# sign the resulting transactions
# copy the output from the previous command into spell_prove_result:


spell_prove_result='["0200000001d0...000","020000000001041...000"]'


signed_commit_tx=$(b signrawtransactionwithwallet $(echo $spell_prove_result | jq -r '.[0]') | jq -r '.hex')


signed_spell_tx=$(b signrawtransactionwithwallet $(echo $spell_prove_result | jq -r '.[1]') $(b decoderawtransaction $signed_commit_tx | jq -c '[{txid: .txid, vout: .vout[0].n, scriptPubKey: .vout[0].scriptPubKey.hex, amount: .vout[0].value}]') | jq -r '.hex')


b submitpackage '["'$signed_commit_tx'","'$signed_spell_tx'"]'