Spacechains Mining Implementation

Intro

This project reimplements the spacechain proposal.

Some improvements over the original design:

• The covenant's private key is no longer in the code. All covenant transaction are pre-signed and stored in covenant.db.

• Instead of using P2SH, all transactions are P2WSH, so they cannot be malleated.

• Instead of manually calling the Bitcoin-Core wallet, it uses BDK, improving the UX and automating all the steps.

Caveats

Currently covenant.db is only configured for testnet covenant pre-signed transactions.

But a covenant.db for signet can be via spacechain generator project.

Do not generate it for mainnet. The code is not reviewed and will result in irreversible loss of funds.

Tutorial

0 - Clone the project and build

$ git clone git@github.com:w0xlt/spacechain-v0.git
$ cd spacechain-v0
$ cargo build --release
$ cd target
$ cd release
$ cp ../../convenant.db .

By default, a configuration file is created in $HOME/.spacechains/spacechains.conf. When executing any comand below, the software will try to connect to the Blockstream's testnet server ssl://electrum.blockstream.info:60002. If different settings are required, the file should be edited.

1 - Create or Import a wallet

To create a new wallet, run:

$ spacechains create-wallet w1

Wallet created successfully !

Alternatively, a wallet can be imported. This can be used when the user already has a funded wallet.

cargo run import-wallet "w2" "wpkh(tprv8ZgxMBicQKsPcyyLXWZPp4Xt7jKNDKvMZBhu195bqp2Hv2nvTEtziqpr4cZcJiEKdUD1AD9CoGUihrgmjoXukFbDEtLptcyinEbPQjouBhH/84'/1'/0'/0/*)#tqeruafe" "wpkh(tprv8ZgxMBicQKsPcyyLXWZPp4Xt7jKNDKvMZBhu195bqp2Hv2nvTEtziqpr4cZcJiEKdUD1AD9CoGUihrgmjoXukFbDEtLptcyinEbPQjouBhH/84'/1'/0'/1/*)#65uzpgep"

w1 and w2 are the wallet names. Any name can be used.

2 - Get a new address and fund it

Then run the software with the following command to get a new address. If a wallet does not exist, this command will create one.

$ spacechains get-new-address w1
{
  "address": "tb1qqe2xuqa4kt5j40tfd0m2820q9njxpd23tse2wp",
  "index": 0
}

Note that the wallet was created in $HOME/.spacechains. The keys of all wallets are stored in $HOME/.spacechains/wallet.db.

Proceed to the testnet faucet and send some coins on the address indicated in the terminal.

3 - Check wallet balance

The wallet balance can be checked with the following command:

$ spacechains get-balance w1
{
  "confirmed": 1349017,
  "immature": 0,
  "trusted_pending": 0,
  "untrusted_pending": 0
}

Wait until the balance is confirmed and proceed to the next step. This may take a while.

3 - Mine a new block

The mine command will create and broadcast the covenant and the fee-bumping CPFP transactions.

If broadcasted successfully, the command will return the id of both transactions.

$ spacechains mine w1 "Hello World" 100000

{
  "covenant_transaction_id": "0e5dbbb78236116f741399e617048d2ebc7e4c6b3d5038306afea4d776acd2a7",
  "cpfp_transaction_id": "1c5ec24460adf9d020d1556d15a571e24546e5ee2693c5c1b6dd12a9472a09c1"
}

The first is the data to be include in the OP_RETURN output of the fee-bumping CPFP transaction.

The second parameter is the fee amount to be paid. This must be less than the confirmed wallet balance.

4 - Backup wallet

The backup command shows the private descriptor. With this, the wallet can be exported to Bitcoin Core or others that support descriptors.

$ spacechains backup w1

{
  "blockheight": 116443,
  "descriptor": "wpkh(tprv8ZgxMBicQKsPcyyLXWZPp4Xt7jKNDKvMZBhu195bqp2Hv2nvTEtziqpr4cZcJiEKdUD1AD9CoGUihrgmjoXukFbDEtLptcyinEbPQjouBhH/84'/1'/0'/0/*)",
  "label": "exported wallet"
}

5 - Config File

The command config_file displays the configurable parameters the user can customize.

The blockchain option can be bitcoin_rpc and electrum.

For now, only signet and testnet options are supported.

Other options can be changed according to user's Electrum, bitcoind settings.

The first line shows where the file is located. By default it is in $HOME/.spacechains/spacechains.conf

$ spacechains config-file

Config file located in /home/node/.spacechains/spacechains.conf
{
  "bitcoind_auth_file": "/home/node/.bitcoin/signet/.cookie",
  "bitcoind_url": "127.0.0.1:38332",
  "blockchain": "electrum",
  "electrum_url": "ssl://electrum.blockstream.info:60002",
  "network": "testnet"
}