Basic Substrate Blockchain

A UTXO (Unspent Transaction Output) chain implementation on Substrate.

Installation

1. Install or update Rust

curl https://sh.rustup.rs -sSf | sh

rustup update nightly
rustup target add 
rustup update stable

UI Demo

In this UI demo, you will interact with the UTXO blockchain via the Polkadot UI.

The following example takes you through a scenario where:

• Alice already owns a UTXO of value 100 upon genesis
• Alice sends Bob a UTXO with value 50, tipping the remainder to validators

1. Compile and build a release node

cargo +nightly build --release

2. Start a node. The --dev flag will start a single mining node, and the --tmp flag will start it in a new temporary directory.

./target/release/utxo-workshop --dev --tmp

3. In the console note the helper printouts. In particular, notice the default account Alice already has 100 UTXO within the genesis block.

4. Open Polkadot JS making sure the client is connected to your local node by going to Settings > General and selecting Local Node in the remote node dropdown.

5. Declare custom datatypes in PolkadotJS as the frontend cannot automatically detect this information. To do this, go to Settings > Developer tab and paste in the following JSON:

{
  "Address": "AccountId",
  "LookupSource": "AccountId",
  "Value": "u128",
  "TransactionInput": {
    "outpoint": "Hash",
    "sigscript": "H512"
  },
  "TransactionOutput": {
    "value": "Value",
    "pubkey": "Hash"
  },
  "Transaction": {
    "inputs": "Vec<TransactionInput>",
    "outputs": "Vec<TransactionOutput>"
  },
  "Difficulty": "U256",
  "DifficultyAndTimestamp": {
    "difficulty": "Difficulty",
    "timestamp": "Moment"
  },
  "Public": "H256"
}

6. Confirm that Alice already has 100 UTXO at genesis. In Chain State > Storage, select utxo. Input the hash 0x76584168d10a20084082ed80ec71e2a783abbb8dd6eb9d4893b089228498e9ff. Click the + notation to query blockchain state.

   Notice that:

   • This UTXO has a value of 100
   • This UTXO belongs to Alice's pubkey. You use the subkey tool to confirm that the pubkey indeed belongs to Alice

7. Spend Alice's UTXO, giving 50 to Bob. In the Extrinsics tab, invoke the spend function from the utxo pallet, using Alice as the transaction sender. Use the following input parameters:

   • outpoint: 0x76584168d10a20084082ed80ec71e2a783abbb8dd6eb9d4893b089228498e9ff
   • sigscript: 0x6ceab99702c60b111c12c2867679c5555c00dcd4d6ab40efa01e3a65083bfb6c6f5c1ed3356d7141ec61894153b8ba7fb413bf1e990ed99ff6dee5da1b24fd83
   • value: 50
   • pubkey: 0x8eaf04151687736326c9fea17e25fc5287613693c912909cb226aa4794f26a48

   Send as an unsigned transaction. With UTXO blockchains, the proof is already in the sigscript input.

8. Verify that your transaction succeeded. In Chain State, look up the newly created UTXO hash: 0xdbc75ab8ee9b83dcbcea4695f9c42754d94e92c3c397d63b1bc627c2a2ef94e6 to verify that a new UTXO of 50, belonging to Bob, now exists! Also you can verify that Alice's original UTXO has been spent and no longer exists in UtxoStore.