Implement calculation of genesis blocks

Author: philipr-za

src/genesis.rs

@@ -0,0 +1,255 @@
+// Rust Elements Library
+// Written by
+//   The Elements developers
+//
+// To the extent possible under law, the author(s) have dedicated all
+// copyright and related and neighboring rights to this software to
+// the public domain worldwide. This software is distributed without
+// any warranty.
+//
+// You should have received a copy of the CC0 Public Domain Dedication
+// along with this software.
+// If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
+//
+
+//! Helpers to calculate the genesis block for a given network.
+
+use bitcoin::secp256k1::impl_array_newtype;
+use secp256k1_zkp::Tweak;
+use crate::hashes::{sha256, sha256d, Hash, HashEngine};
+use crate::opcodes::all::OP_RETURN;
+use crate::opcodes::OP_TRUE;
+use crate::pset::serialize::Serialize;
+use crate::{confidential, script, AssetId, Block, BlockExtData, BlockHash, BlockHeader, LockTime, Script, Sequence, Transaction, TxIn, TxInWitness, TxOut, TxOutWitness};
+use crate::{AssetIssuance, ContractHash, OutPoint, Txid};
+use crate::confidential::Nonce;
+
+/// Parameters that influence chain consensus. The contents of the genesis block for a given network
+/// are defined by these values.
+#[derive(Clone, Debug)]
+pub struct NetworkParams {
+    /// The network identifier string that elementsd accepts as the `chain` config argument
+    pub network_id: String,
+    /// This network's Fedpeg script
+    pub fedpeg_script: Script,
+    /// This network's `sign_block_script`
+    pub sign_block_script: Script,
+    /// How many free coins are present in this network
+    pub initial_free_coins: u64,
+}
+
+impl NetworkParams {
+    /// New custom network params
+    pub fn new(
+        network_id: String,
+        fedpeg_script: Script,
+        sign_block_script: Script,
+        initial_free_coins: u64,
+    ) -> NetworkParams {
+        NetworkParams {
+            network_id,
+            fedpeg_script,
+            sign_block_script,
+            initial_free_coins,
+        }
+    }
+
+    /// Network params for Liquid mainnet
+    pub fn liquidv1() -> Self {
+        NetworkParams {
+            network_id: "liquidv1".to_string(),
+            // Can be verified at https://github.com/ElementsProject/elements/blob/27c2fb6b7de404908f9ef2eb5c98c9989d1ab8e4/src/chainparams.cpp#L1243
+            fedpeg_script: Script::from_hex_no_prefix("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").expect("constant fedpeg script parse"),
+            // Can be verified at https://github.com/ElementsProject/elements/blob/27c2fb6b7de404908f9ef2eb5c98c9989d1ab8e4/src/chainparams.cpp#L1193
+            sign_block_script: Script::from_hex_no_prefix("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").expect("constant sign_block_script parse"),
+            initial_free_coins: 0,
+        }
+    }
+
+    /// Network params for Liquid testnet
+    pub fn liquidtestnet() -> Self {
+        NetworkParams {
+            network_id: "liquidtestnet".to_string(),
+            fedpeg_script: script::Builder::new().push_opcode(OP_TRUE).into_script(),
+            // Can be verified at https://github.com/ElementsProject/elements/blob/27c2fb6b7de404908f9ef2eb5c98c9989d1ab8e4/src/chainparams.cpp#L1108
+            sign_block_script: Script::from_hex_no_prefix("51210217e403ddb181872c32a0cd468c710040b2f53d8cac69f18dad07985ee37e9a7151ae").expect("constant sign_block_script parse"),
+            initial_free_coins: 2_100_000_000_000_000,
+        }
+    }
+
+    /// Network params for a custom Elements network with defaults
+    pub fn custom_network(network_id: String, fedpeg_script: Option<Script>, sign_block_script: Option<Script>, initial_free_coins: Option<u64>) -> Self {
+        NetworkParams {
+            network_id,
+            fedpeg_script: fedpeg_script.unwrap_or_else(|| script::Builder::new().push_opcode(OP_TRUE).into_script()),
+            sign_block_script: sign_block_script.unwrap_or_else(|| script::Builder::new().push_opcode(OP_TRUE).into_script()),
+            initial_free_coins: initial_free_coins.unwrap_or(0),
+        }
+    }
+}
+
+/// Hash commitment of network parameters for a given Network
+pub fn commit_to_custom_network_parameters(params: &NetworkParams) -> Vec<u8> {
+    let mut eng = sha256::Hash::engine();
+    eng.input(params.network_id.clone().as_bytes());
+    eng.input(format!("{:x}", params.fedpeg_script).as_bytes());
+    eng.input(format!("{:x}", params.sign_block_script).as_bytes());
+    sha256::Hash::from_engine(eng).serialize()
+}
+
+/// Produce the genesis transaction for a given elements Network
+fn liquid_genesis_tx(network_params: &NetworkParams) -> Transaction {
+    let commit = commit_to_custom_network_parameters(network_params);
+
+    let input = TxIn {
+        previous_output: OutPoint::default(),
+        is_pegin: false,
+        script_sig: script::Builder::new()
+            .push_slice(commit.as_slice())
+            .into_script(),
+        sequence: Sequence::default(),
+        asset_issuance: AssetIssuance::default(),
+        witness: TxInWitness::default(),
+    };
+
+    let output = TxOut {
+        asset: confidential::Asset::Explicit(AssetId::default()),
+        value: confidential::Value::Explicit(0),
+        nonce: Nonce::default(),
+        script_pubkey: script::Builder::new().push_opcode(OP_RETURN).into_script(),
+        witness: TxOutWitness::default(),
+    };
+
+    Transaction {
+        version: 1,
+        lock_time: LockTime::ZERO,
+        input: vec![input],
+        output: vec![output],
+    }
+}
+
+/// Create the confidential asset transaction for the genesis block if required by the specified Network
+fn liquid_genesis_asset_tx(network_params: &NetworkParams) -> Option<Transaction> {
+    let commit = commit_to_custom_network_parameters(network_params);
+    let asset_amount = network_params.initial_free_coins;
+    if asset_amount == 0 {
+        return None;
+    }
+    let asset_outpoint = OutPoint::new(Txid::from_slice(commit.as_slice()).expect("txid"), 0);
+    let contract_hash = ContractHash::from_byte_array([0u8; 32]);
+    let asset_entropy = AssetId::generate_asset_entropy(asset_outpoint, contract_hash);
+    let asset_id = AssetId::from_entropy(asset_entropy);
+
+    let asset_issuance = AssetIssuance {
+        asset_blinding_nonce: Tweak::default(),
+        asset_entropy: [0u8; 32],
+        amount: confidential::Value::Explicit(asset_amount),
+        inflation_keys: confidential::Value::Explicit(0),
+    };
+
+    let input = TxIn {
+        previous_output: asset_outpoint,
+        is_pegin: false,
+        script_sig: Script::new(),
+        sequence: Sequence::default(),
+        asset_issuance,
+        witness: TxInWitness::default(),
+    };
+
+    let output = TxOut {
+        asset: confidential::Asset::Explicit(asset_id),
+        value: confidential::Value::Explicit(asset_amount),
+        nonce: Nonce::default(),
+        script_pubkey: script::Builder::new().push_opcode(OP_TRUE).into_script(),
+        witness: TxOutWitness::default(),
+    };
+
+    let ret = Transaction {
+        version: 1,
+        lock_time: LockTime::ZERO,
+        input: vec![input],
+        output: vec![output],
+    };
+    Some(ret)
+}
+
+/// Constructs and returns the Liquid genesis blocks assuming default consensus parameters
+/// Does not return upstream bitcoin network blocks as they are a different format and can be
+/// acquired from the `rust-bitcoin` library
+pub fn genesis_block(params: &NetworkParams) -> Block {
+    let tx = liquid_genesis_tx(params);
+    let mut txdata = vec![tx.clone()];
+
+    let merkle_root: sha256d::Hash =
+        if let Some(asset_tx) = liquid_genesis_asset_tx(params) {
+            txdata.push(asset_tx.clone());
+            let tx_hashes = vec![tx.txid().to_raw_hash(), asset_tx.txid().to_raw_hash()];
+            bitcoin::merkle_tree::calculate_root(tx_hashes.into_iter())
+                .expect("merkle root")
+        } else {
+            tx.txid().to_raw_hash()
+        };
+
+    Block {
+        header: BlockHeader {
+            version: 1,
+            prev_blockhash: BlockHash::all_zeros(),
+            merkle_root: merkle_root.into(),
+            time: 1_296_688_602,
+            height: 0,
+            ext: BlockExtData::Proof {
+                challenge: params.sign_block_script.clone(),
+                solution: Script::default(),
+            },
+        },
+        txdata,
+    }
+}
+/// The uniquely identifying hash of the target blockchain.
+/// Liquid networks assume default consensus constants, Elements allows for modification of fedpeg and signblock scripts
+/// via configuration argument which will cause these values to differ so these are only for default parameters
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct ChainHash([u8; 32]);
+impl_array_newtype!(ChainHash, u8, 32);
+
+impl ChainHash {
+    /// `ChainHash` for Liquid v1 mainnet.
+    pub const LIQUIDV1: Self = Self([
+        3, 96, 32, 138, 136, 150, 146, 55, 44, 141, 104, 176, 132, 166, 46, 253, 246, 14, 161, 163,
+        89, 160, 76, 148, 178, 13, 34, 54, 88, 39, 102, 20,
+    ]);
+    /// `ChainHash` for Liquid testnet.
+    pub const LIQUIDTESTNET: Self = Self([
+        193, 177, 106, 226, 79, 36, 35, 174, 162, 234, 52, 85, 34, 146, 121, 59, 91, 94, 130, 153,
+        154, 30, 237, 129, 213, 106, 238, 82, 142, 218, 113, 167,
+    ]);
+
+    /// Calculates the chainhash for a set of network parameters
+    pub fn for_params(params: &NetworkParams) -> Self {
+        let genesis_block = genesis_block(params);
+        ChainHash(genesis_block.block_hash().to_byte_array())
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::genesis::{genesis_block, ChainHash, NetworkParams};
+    use crate::hashes::Hash;
+
+    #[test]
+    fn genesis_block_hash() {
+        let genesis_block = genesis_block(&NetworkParams::liquidv1());
+        assert_eq!(
+            genesis_block.block_hash().to_byte_array(),
+            ChainHash::LIQUIDV1.0
+        );
+
+        let genesis_block =
+            crate::genesis::genesis_block(&NetworkParams::liquidtestnet());
+
+        assert_eq!(
+            genesis_block.block_hash().to_byte_array(),
+            ChainHash::LIQUIDTESTNET.0
+        );
+    }
+}

src/lib.rs

@@ -73,6 +73,8 @@ pub mod taproot;
 mod transaction;
 // consider making upstream public
 mod endian;
+pub mod genesis;
+
 // re-export bitcoin deps which we re-use
 pub use bitcoin::hashes;
 // export everything at the top level so it can be used as `elements::Transaction` etc.