bitcoin-da:

This package provides a reader / writer interface to bitcoin.

Example:

// ExampleRelayer_Read tests that reading data from the blockchain works as
// expected.
func ExampleRelayer_Read() {
	// Example usage
	relayer, err := bitcoinda.NewRelayer(bitcoinda.Config{
		Host:         "localhost:18332",
		User:         "rpcuser",
		Pass:         "rpcpass",
		HTTPPostMode: true,
		DisableTLS:   true,
	})
	if err != nil {
		fmt.Println(err)
		return
	}
	_, err = relayer.Write([]byte("rollkit-btc: gm"))
	if err != nil {
		fmt.Println(err)
		return
	}
	// TODO: either mock or generate block
	// We're assuming the prev tx was mined at height 146
	height := uint64(146)
	blobs, err := relayer.Read(height)
	if err != nil {
		fmt.Println(err)
		return
	}
	for _, blob := range blobs {
		got, err := hex.DecodeString(fmt.Sprintf("%x", blob))
		if err != nil {
			fmt.Println(err)
			return
		}
		fmt.Println(string(got))
	}
	// Output: rollkit-btc: gm
}

Tests:

Running the tests requires a local regtest node.

bitcoind -chain=regtest -rpcport=18332 -rpcuser=rpcuser -rpcpassword=rpcpass -fallbackfee=0.000001 -txindex=1

bitcoin-cli -regtest -rpcport=18332 -rpcuser=rpcuser -rpcpassword=rpcpass createwallet w1

export COINBASE=$(bitcoin-cli -regtest -rpcport=18332 -rpcuser=rpcuser -rpcpassword=rpcpass getnewaddress)

bitcoin-cli -regtest -rpcport=18332 -rpcuser=rpcuser -rpcpassword=rpcpass generatetoaddress 101 $COINBASE

Idle for a while till coinbase coins mature.

=== RUN   ExampleRelayer_Write
--- PASS: ExampleRelayer_Write (0.13s)
=== RUN   ExampleRelayer_Read
--- PASS: ExampleRelayer_Read (0.10s)
PASS
ok      github.com/rollkit/bitcoin-da   0.375s

Writer:

A commit transaction containing a taproot with one leaf script

OP_FALSE
OP_IF
  "roll" marker
  <embedded data>
OP_ENDIF
<pubkey>
OP_CHECKSIG

is used to create a new bech32m address and is sent an output.

A reveal transaction then posts the embedded data on chain and spends the commit output.

Reader:

The address of the reveal transaction is implicity used as a namespace.

Clients may call listunspent on the reveal transaction address to get a list of transactions and read the embedded data from the first witness input.

Spec:

For more details, read the spec