- Download bitcoin core
- Unpack it wherever you want.
- Create a directory named
data
inside the unpacked folder. - Create a directory named
.bitcoin
inside your home folder:mkdir ~/.bitcoin
- Copy bitcoin.conf into
~/.bitcoin
- Copy rpcauth into
<unpacked_folder>/share/rpcauth
- Run
<unpacked_folder>/share/rpcauth/rpcauth.py <YOUR_USERNAME>
. Keep the output somewhere, you'll need it later. - Edit your
bitcoin.conf
. - Uncomment
regtest=0
and enable it:regtest=1
- Uncomment
rpcuser=alice
and replace the value with your username. - Uncomment
rpcpassword=...
and replace the value with the password you got fromrpcauth
. - Uncomment
rpcauth=bob:...
and replace the value with the line you got fromrpcauth
. - (Optionnal) Append
datadir=<unpacked_folder>/data
to the end of the file, where<unpacked_folder>
is the absolute path to your unpacked folder. - Run
<unpacked_folder>/bin/bitcoind
- Open another terminal, and run
<unpacked_folder>/bin/bitcoin-cli getbalance
. It should return0
.
Your first node is set. Now let's setup another one to connect to. We need to use another port and another data dir.
Run: bitcoind -port=18445 -rpcport=8333 -datadir=<unpacked_folder>/data2
We'll start by generating a new wallet address. We will use it for all our future operations, so keep it somewhere.
bitcoin-cli getnewaddress
bitcoin-cli generatetoaddress 50 <youraddress>
# Check the blocks are mined
bitcoin-cli getblockcount # Should return 50
Let's connect to our second node: bitcoin-cli addnode "127.0.0.1:18445" add
.
To keep the connection after a restart, add the following to your bitcoin.conf
: addnode=127.0.0.1:18445
Check if your nodes are connected: bitcoin-cli getaddednodeinfo
.
Now check if the second node is synchronized: bitcoin-cli -rpcport=8333 getblockcount
.
Let's mine some blocks and check if everything is synchronized:
bitcoin-cli generatetoaddress 25 "<your_address>"
bitcoin-cli getblockcount # Should return 75
bitcoin-cli -rpcport=8333 getblockcount # Should return 75
We got some funds from mining the first blocks. We will transfer them to our wallet on the second node.
address=`bitcoin-cli -rpcport=8333 getnewaddress`
bitcoin-cli sendtoaddress "$1" 10
# Check the funds have been received
address=`bitcoin-cli -rpcport=8333 getwalletinfo`
As we only have two nodes in the network, it's easy to make a 51% attack. We're going to double spend some bitcoin.
# Get a unspent output with a non-zero output
bitcoin-cli listunspent
# Create a raw transaction and sign it
# Don't forget to set the amount of your vout a little bit lower than the amount of your utxo so your tx has fees
transaction=`bitcoin-cli createrawtransaction '[{"txid":"<TX_ID>","vout":0}]' '{"$address":12.49}'`
bitcoin-cli signrawtransactionwithwallet "$transaction"
Keep the generated hex of the signed transaction. We need to disconnect both nodes and broadcast the transaction from the other node.
# Disconnect nodes
bitcoin-cli disconnectnode "127.0.0.1:18445"
bitcoin-cli -rpcport=8333 disconnectnode "127.0.0.1:18444"
# Broadcast from other node
bitcoin-cli -rpcport=8333 sendrawtransaction "<HEX>"
To make a double spend, we need to create another transaction with the same utxo and broadcast it on the chain where the first one wasn't broadcasted.
# Generate a second address to make it easier to differenciate both transactions
address=`bitcoin-cli -rpcport=8333 getnewaddress`
transaction=`bitcoin-cli createrawtransaction '[{"txid":"<TX_ID>","vout":0}]' '{"$address":12.49}'`
bitcoin-cli signrawtransactionwithwallet "$transaction"
bitcoin-cli sendrawtransaction "<HEX>"
We need to mine some blocks so when we join the two nodes, the longest chain is kept. (In our case, the one with the second transaction).
bitcoin-cli generate 50
# Join
bitcoin-cli addnode "127.0.0.1:18445" add
Check that the first transaction doesn't exist anymore:
bitcoin-cli -rpcport=8333 listtransactions
The last one should have the address we used for the second transaction. The double-spend worked!