An implementation of the Ark second-layer payment protocol for Bitcoin.

This repository comprises an ASP server, aspd, a client wallet, bark, and a library that contains all the primitives used for these implementations.

The ark_demo.sh script creates a nice environment to play with ark.

source ark_demo.sh

First you have to setup a regtest bicoind node. If you already have a regtest-node you can use that one. You just have to ensure that txindex is enabled. However, the tutorial is easier to follow if you spin up a new regtest node.

bd --daemon

You can always use type -a bd to see what the alias does. In this case it will tell you that bd is an alias for bitcoind -regtest -datadir=/ark/test/bitcoindatadir -server -txdindex.

You can use the bitcoin-cli which is aliased to bcli to interact with the node.

bcli getnetworkinfo

Then we create and configure an ark-server using the aspd-command. Our ark-server will run on regtest and use the bitcoin-node we've started a few lines before.

aspd create \
    --network regtest \
    --datadir ./test/arkdatadir \
    --bitcoind-url $BITCOIND_URL \
    --bitcoind-cookie $BITCOIND_COOKIE

The server can be started using

aspd start --datadir ./test/arkdatadir

The server will start working immediately but requires some funds to work properly. You can find an the onchain address in the logs and send some funds to it.

bcli generatetoaddress 1 <asp-addr>

The funds are only useable after we generate 100 extra blocks.

bcli generatetoaddress 100 mtDDKi5mDjZqGzmbnfUnVQ8ZhCPMPVsApj

Next, you can start some clients. To create a client, use the following command:

bark --datadir ./test/bark1 create \
    --regtest \
    --asp https://localhost:3535 \
    --bitcoind $BITCOIND_URL \
    --bitcoind-cookie $BITCOIND_COOKIE

bark --datadir ./test/bark2 create \
    --regtest \
    --asp https://localhost:3535 \
    --bitcoind $BITCOIND_URL \
    --bitcoind-cookie $BITCOIND_COOKIE

These will create individual wallets and print an on-chain address you can use to fund them the same way as you did for the ASP above. Note that clients can receive off-chain Ark transactions without having any on-chain balance, but a little bit of on-chain money is needed to perform unilateral exits.

You can find the wallet using

BARK1_ADDR=$(bark --datadir ./test/bark1 get-address)
bcli generatetoaddress 1 $BARK1_ADDR
bcli generatetoaddress 100 mtDDKi5mDjZqGzmbnfUnVQ8ZhCPMPVsApj

To use the onchain wallets, there are a few commands available:

BARK2_ADDR=$(bark --datadir ./test/bark2 get-address)
bark --datadir ./test/bark1 send-onchain $BARK2_ADDR "0.1 btc"
bark --datadir ./test/bark2 balance

Once we have money, we can onboard into the Ark, afterwards the balance will also show an off-chain element.

bark --datadir ./test/bark1 onboard "1 btc"
bark --datadir ./test/bark1 balance

Remember that all txs will just be in the mempool if you don't generate blocks once a while...

bcli generatetoaddress 1 mtDDKi5mDjZqGzmbnfUnVQ8ZhCPMPVsApj

Then, let's send some money off-chain:

## Should be empty..
BARK2_PK=$(bark --datadir ./test/bark2 get-vtxo-pubkey)
# For now every client has just a single pubkey.
echo "${BARK2_PK}"
bark --datadir ./test/bark1 send-round ${BARK2_PK} "0.1 btc"
bark --datadir ./test/bark2 balance

You will notice that there is a slight delay when sending, this is because the client needs to wait for the start of the next round and currently no out-of-round payments are supported. The round interval can be changed in the aspd configuration.