consensus: Reviewed implementation.

Cargo.toml

@@ -206,8 +206,11 @@ blockchain = [
 
 blockchain2 = [
     "blake3",
+    "chrono",
     "sled",
 
+    "crypto",
+    "net",
     "util",
 ]
 

src/blockchain2/blockstore.rs

@@ -1,58 +1,54 @@
 use sled::Batch;
 
 use crate::{
-    util::serial::{deserialize, serialize, SerialDecodable, SerialEncodable},
+    consensus2::{util::Timestamp, Block},
+    util::serial::{deserialize, serialize},
     Result,
 };
 
 const SLED_BLOCK_TREE: &[u8] = b"_blocks";
 
-// TODO: The block structure should be as follows
-#[derive(Debug, Clone, SerialEncodable, SerialDecodable)]
-pub struct Block {
-    /// Previous block hash (blake3)
-    pub st: blake3::Hash,
-    /// Slot UID, generated by the beacon
-    pub sl: u64,
-    /// Transaction hashes (blake3)
-    /// The actual transactions are in [`TxStore`]
-    pub txs: Vec<blake3::Hash>,
-    /// Additional block information
-    pub metadata: String,
-}
-
 pub struct BlockStore(sled::Tree);
 
 impl BlockStore {
-    /// Opens a new or existing blockstore tree given a sled database.
-    pub fn new(db: &sled::Db) -> Result<Self> {
+    /// Opens a new or existing `BlockStore` on the given sled database.
+    /// The database is typically initialized as a global instance reference
+    /// with e.g. lazy_static.
+    pub fn new(db: &sled::Db, genesis_ts: Timestamp, genesis_data: blake3::Hash) -> Result<Self> {
         let tree = db.open_tree(SLED_BLOCK_TREE)?;
-        Ok(Self(tree))
+        let store = Self(tree);
+
+        // In case the store is empty, create the genesis block.
+        if store.0.is_empty() {
+            store.insert(&[Block::genesis_block(genesis_ts, genesis_data)])?;
+        }
+
+        Ok(store)
     }
 
-    /// Insert a vector of [`Block`] into the blockstore.
-    /// The blocks are hashed with blake3 and this blockhash is used as
-    // the key, where value is the serialized block itself.
-    pub fn insert(&self, blocks: Vec<Block>) -> Result<()> {
+    /// Insert a slice of [`Block`] into the blockstore. With sled, the
+    /// operation is done as a batch.
+    /// The blocks are hashed with BLAKE3 and this blockhash is used as
+    /// the key, where value is the serialized block itself.
+    pub fn insert(&self, blocks: &[Block]) -> Result<()> {
         let mut batch = Batch::default();
-        for i in &blocks {
+        for i in blocks {
             let serialized = serialize(i);
             let blockhash = blake3::hash(&serialized);
             batch.insert(blockhash.as_bytes(), serialized);
         }
 
         self.0.apply_batch(batch)?;
-
         Ok(())
     }
 
     /// Fetch given blockhashes from the blockstore.
     /// The resulting vector contains `Option` which is `Some` if the block
     /// was found in the blockstore, and `None`, if it has not.
-    pub fn get(&self, blockhashes: Vec<blake3::Hash>) -> Result<Vec<Option<Block>>> {
+    pub fn get(&self, blockhashes: &[blake3::Hash]) -> Result<Vec<Option<Block>>> {
         let mut ret: Vec<Option<Block>> = Vec::with_capacity(blockhashes.len());
 
-        for i in &blockhashes {
+        for i in blockhashes {
             if let Some(found) = self.0.get(i.as_bytes())? {
                 let block = deserialize(&found)?;
                 ret.push(Some(block));
@@ -69,6 +65,7 @@ impl BlockStore {
         Ok(self.0.contains_key(blockhash.as_bytes())?)
     }
 
+    /*
     /// Fetch the first block in the tree, based on the Ord implementation for Vec<u8>.
     pub fn get_first(&self) -> Result<Option<(blake3::Hash, Block)>> {
         if let Some(found) = self.0.first()? {
@@ -131,4 +128,5 @@ impl BlockStore {
 
         self.0.range(start..end)
     }
+    */
 }

src/blockchain2/metadatastore.rs

@@ -0,0 +1,20 @@
+use crate::{consensus2::StreamletMetadata, util::serial::serialize, Result};
+
+const SLED_STREAMLET_METADATA_TREE: &[u8] = b"_streamlet_metadata";
+
+pub struct StreamletMetadataStore(sled::Tree);
+
+impl StreamletMetadataStore {
+    pub fn new(db: &sled::Db) -> Result<Self> {
+        let tree = db.open_tree(SLED_STREAMLET_METADATA_TREE)?;
+        Ok(Self(tree))
+    }
+
+    /// Insert [`StreamletMetadata`] into the `MetadataStore`.
+    /// The blockhash for the metadata is used as the key,
+    /// where value is the serialized metadata.
+    pub fn insert(&self, block: blake3::Hash, metadata: &StreamletMetadata) -> Result<()> {
+        self.0.insert(block.as_bytes(), serialize(metadata))?;
+        Ok(())
+    }
+}

src/blockchain2/mod.rs

@@ -1,38 +1,51 @@
 use std::io;
 
 use crate::{
+    consensus2::{block::BlockProposal, util::Timestamp},
     impl_vec,
     util::serial::{Decodable, Encodable, ReadExt, VarInt, WriteExt},
     Result,
 };
 
 pub mod blockstore;
-pub mod nfstore;
-pub mod rootstore;
-pub mod txstore;
-
 use blockstore::BlockStore;
+
+pub mod metadatastore;
+use metadatastore::StreamletMetadataStore;
+
+pub mod nfstore;
 use nfstore::NullifierStore;
+
+pub mod rootstore;
 use rootstore::RootStore;
+
+pub mod txstore;
 use txstore::TxStore;
 
 pub struct Blockchain {
-    pub db: sled::Db,
+    /// Blocks sled tree
     pub blocks: BlockStore,
+    /// Transactions sled tree
     pub transactions: TxStore,
-    pub nullifiers: NullifierStore,
-    pub merkle_roots: RootStore,
+    /// Streamlet metadata sled tree
+    pub streamlet_metadata: StreamletMetadataStore,
+    // TODO:
+    //pub nullifiers: NullifierStore,
+    //pub merkle_roots: RootStore,
 }
 
 impl Blockchain {
-    pub fn new(db_path: &str) -> Result<Self> {
-        let db = sled::open(db_path)?;
-        let blocks = BlockStore::new(&db)?;
-        let transactions = TxStore::new(&db)?;
-        let nullifiers = NullifierStore::new(&db)?;
-        let merkle_roots = RootStore::new(&db)?;
-
-        Ok(Self { db, blocks, transactions, nullifiers, merkle_roots })
+    pub fn new(db: &sled::Db, genesis_ts: Timestamp, genesis_data: blake3::Hash) -> Result<Self> {
+        let blocks = BlockStore::new(db, genesis_ts, genesis_data)?;
+        let transactions = TxStore::new(db)?;
+        let streamlet_metadata = StreamletMetadataStore::new(db)?;
+
+        Ok(Self { blocks, transactions, streamlet_metadata })
+    }
+
+    /// Batch insert [`BlockProposal`]s.
+    pub fn add(&mut self, proposals: &[BlockProposal]) -> Result<Vec<blake3::Hash>> {
+        todo!()
     }
 }
 

src/consensus2/block.rs

@@ -0,0 +1,179 @@
+use std::io;
+
+use log::warn;
+
+use super::{util::Timestamp, Metadata, StreamletMetadata, Tx};
+use crate::{
+    crypto::{keypair::PublicKey, schnorr::Signature},
+    impl_vec, net,
+    util::serial::{serialize, Decodable, Encodable, SerialDecodable, SerialEncodable, VarInt},
+    Result,
+};
+
+/// This struct represents a tuple of the form (`st`, `sl`, txs`, `metadata`).
+#[derive(Debug, Clone, SerialEncodable, SerialDecodable)]
+pub struct Block {
+    /// Previous block hash
+    pub st: blake3::Hash,
+    /// Slot uid, generated by the beacon
+    pub sl: u64,
+    /// Transaction hashes
+    pub txs: Vec<blake3::Hash>,
+    /// Additional block information
+    pub metadata: Metadata,
+}
+
+impl Block {
+    pub fn new(st: blake3::Hash, sl: u64, txs: Vec<blake3::Hash>, metadata: Metadata) -> Self {
+        Self { st, sl, txs, metadata }
+    }
+
+    /// Generate the genesis block.
+    pub fn genesis_block(genesis_ts: Timestamp, genesis_data: blake3::Hash) -> Self {
+        let metadata =
+            Metadata::new(genesis_ts, String::from("proof"), String::from("r"), String::from("s"));
+
+        Self::new(genesis_data, 0, vec![], metadata)
+    }
+}
+
+/// This struct represents a block proposal, used for consensus.
+#[derive(Debug, Clone, SerialEncodable, SerialDecodable)]
+pub struct BlockProposal {
+    /// Leader public key
+    pub public_key: PublicKey,
+    /// Block signature
+    pub signature: Signature,
+    /// Leader ID
+    pub id: u64,
+    /// Previous block hash
+    pub st: blake3::Hash,
+    /// Slot uid, generated by the beacon
+    pub sl: u64,
+    /// Transactions payload
+    pub txs: Vec<Tx>,
+    /// Additional proposal information
+    pub metadata: Metadata,
+    /// Proposal information used by Streamlet consensus
+    pub sm: StreamletMetadata,
+}
+
+impl BlockProposal {
+    #[allow(clippy::too_many_arguments)]
+    pub fn new(
+        public_key: PublicKey,
+        signature: Signature,
+        id: u64,
+        st: blake3::Hash,
+        sl: u64,
+        txs: Vec<Tx>,
+        metadata: Metadata,
+        sm: StreamletMetadata,
+    ) -> Self {
+        Self { public_key, signature, id, st, sl, txs, metadata, sm }
+    }
+
+    /// Produce proposal hash using `st`, `sl`, `txs`, and `metadata`.
+    pub fn hash(&self) -> blake3::Hash {
+        Self::to_proposal_hash(self.st, self.sl, &self.txs, &self.metadata)
+    }
+
+    /// Generate a proposal hash using provided `st`, `sl`, `txs`, and `metadata`.
+    pub fn to_proposal_hash(
+        st: blake3::Hash,
+        sl: u64,
+        transactions: &[Tx],
+        metadata: &Metadata,
+    ) -> blake3::Hash {
+        let mut txs = Vec::with_capacity(transactions.len());
+        for tx in transactions {
+            txs.push(blake3::hash(&serialize(tx)));
+        }
+
+        blake3::hash(&serialize(&Block::new(st, sl, txs, metadata.clone())))
+    }
+}
+
+impl PartialEq for BlockProposal {
+    fn eq(&self, other: &Self) -> bool {
+        self.public_key == other.public_key &&
+            self.signature == other.signature &&
+            self.id == other.id &&
+            self.st == other.st &&
+            self.sl == other.sl &&
+            self.txs == other.txs &&
+            self.metadata == other.metadata
+    }
+}
+
+impl net::Message for BlockProposal {
+    fn name() -> &'static str {
+        "proposal"
+    }
+}
+
+impl_vec!(BlockProposal);
+
+/// This struct represents a sequence of block proposals.
+#[derive(Debug, Clone, PartialEq, SerialEncodable, SerialDecodable)]
+pub struct ProposalChain {
+    pub genesis: blake3::Hash,
+    pub proposals: Vec<BlockProposal>,
+}
+
+impl ProposalChain {
+    pub fn new(genesis: blake3::Hash, initial_proposal: BlockProposal) -> Self {
+        Self { genesis, proposals: vec![initial_proposal] }
+    }
+
+    /// A proposal is considered valid when its parent hash is equal to the
+    /// hash of the previous proposal and their epochs are incremental,
+    /// excluding the genesis block proposal.
+    /// Additional validity rules can be applied.
+    pub fn check_proposal(&self, proposal: &BlockProposal, previous: &BlockProposal) -> bool {
+        if proposal.st == self.genesis {
+            warn!("Genesis block proposal provided.");
+            return false
+        }
+
+        let prev_hash = previous.hash();
+        if proposal.st != prev_hash || proposal.sl <= previous.sl {
+            warn!("Provided proposal is invalid.");
+            return false
+        }
+
+        true
+    }
+
+    /// A proposals chain is considered valid when every proposal is valid,
+    /// based on the `check_proposal` function.
+    pub fn check_chain(&self) -> bool {
+        for (index, proposal) in self.proposals[1..].iter().enumerate() {
+            if !self.check_proposal(proposal, &self.proposals[index]) {
+                return false
+            }
+        }
+
+        true
+    }
+
+    /// Insertion of a valid proposal.
+    pub fn add(&mut self, proposal: &BlockProposal) {
+        if self.check_proposal(proposal, self.proposals.last().unwrap()) {
+            self.proposals.push(proposal.clone());
+        }
+    }
+
+    /// Proposals chain notarization check.
+    pub fn notarized(&self) -> bool {
+        for proposal in &self.proposals {
+            if !proposal.sm.notarized {
+                return false
+            }
+        }
+
+        true
+    }
+}
+
+impl_vec!(ProposalChain);

src/consensus2/metadata.rs

@@ -0,0 +1,56 @@
+use super::{util::Timestamp, Participant, Vote};
+use crate::util::serial::{SerialDecodable, SerialEncodable};
+
+/// This struct represents additional [`Block`] information used by
+/// the consensus protocol
+#[derive(Debug, Clone, PartialEq, SerialEncodable, SerialDecodable)]
+pub struct Metadata {
+    /// Block creation timestamp
+    pub timestamp: Timestamp,
+    /// Block information used by the Ouroboros Praos consensus
+    pub om: OuroborosMetadata,
+}
+
+impl Metadata {
+    pub fn new(timestamp: Timestamp, proof: String, r: String, s: String) -> Self {
+        Self { timestamp, om: OuroborosMetadata::new(proof, r, s) }
+    }
+}
+
+/// This struct represents [`Block`] information used by the Ouroboros
+/// Praos consensus protocol.
+#[derive(Debug, Clone, PartialEq, SerialEncodable, SerialDecodable)]
+pub struct OuroborosMetadata {
+    /// Proof that the stakeholder is the block owner
+    pub proof: String,
+    /// Random seed for VRF
+    pub r: String,
+    /// Block owner signature
+    pub s: String,
+}
+
+impl OuroborosMetadata {
+    pub fn new(proof: String, r: String, s: String) -> Self {
+        Self { proof, r, s }
+    }
+}
+
+/// This struct represents [`Block`] information used by the Streamlet
+/// consensus protocol.
+#[derive(Debug, Clone, SerialEncodable, SerialDecodable)]
+pub struct StreamletMetadata {
+    /// Epoch votes
+    pub votes: Vec<Vote>,
+    /// Block notarization flag
+    pub notarized: bool,
+    /// Block finalization flag
+    pub finalized: bool,
+    /// Nodes participated in the voting process
+    pub participants: Vec<Participant>,
+}
+
+impl StreamletMetadata {
+    pub fn new(participants: Vec<Participant>) -> Self {
+        Self { votes: vec![], notarized: false, finalized: false, participants }
+    }
+}

src/consensus2/mod.rs

@@ -0,0 +1,35 @@
+/// Block definition
+pub mod block;
+pub use block::{Block, ProposalChain};
+
+/// Transactions
+pub mod tx;
+pub use tx::Tx;
+
+/// Consensus metadata
+pub mod metadata;
+pub use metadata::{Metadata, StreamletMetadata};
+
+/// Consensus participant
+pub mod participant;
+pub use participant::Participant;
+
+/// Consensus vote
+pub mod vote;
+pub use vote::Vote;
+
+/// Consensus state
+pub mod state;
+pub use state::ValidatorState;
+
+/// Utility functions
+pub mod util;
+
+use lazy_static::lazy_static;
+lazy_static! {
+    /// Genesis hash for the mainnet chain
+    pub static ref MAINNET_GENESIS_HASH_BYTES: [u8; 32] = *blake3::hash(b"darkfi_mainnet").as_bytes();
+
+    /// Genesis hash for the testnet chain
+    pub static ref TESTNET_GENESIS_HASH_BYTES: [u8; 32] = *blake3::hash(b"darkfi_testnet").as_bytes();
+}

src/consensus2/participant.rs

@@ -0,0 +1,56 @@
+use std::{collections::BTreeMap, io};
+
+use crate::{
+    impl_vec, net,
+    util::serial::{Decodable, Encodable, SerialDecodable, SerialEncodable, VarInt},
+    Result,
+};
+
+/// This struct represents a tuple of the form:
+/// (`node_id`, `epoch_joined`, `last_epoch_voted`)
+#[derive(Debug, Clone, PartialEq, SerialEncodable, SerialDecodable)]
+pub struct Participant {
+    // Node ID
+    pub id: u64,
+    /// Epoch node joined the network
+    pub joined: u64,
+    /// Last epoch node voted
+    pub voted: Option<u64>,
+}
+
+impl Participant {
+    pub fn new(id: u64, joined: u64) -> Self {
+        Self { id, joined, voted: None }
+    }
+}
+
+impl net::Message for Participant {
+    fn name() -> &'static str {
+        "participant"
+    }
+}
+
+impl Encodable for BTreeMap<u64, Participant> {
+    fn encode<S: io::Write>(&self, mut s: S) -> Result<usize> {
+        let mut len = 0;
+        len += VarInt(self.len() as u64).encode(&mut s)?;
+        for c in self.iter() {
+            len += c.1.encode(&mut s)?;
+        }
+        Ok(len)
+    }
+}
+
+impl Decodable for BTreeMap<u64, Participant> {
+    fn decode<D: io::Read>(mut d: D) -> Result<Self> {
+        let len = VarInt::decode(&mut d)?.0;
+        let mut ret = BTreeMap::new();
+        for _ in 0..len {
+            let participant: Participant = Decodable::decode(&mut d)?;
+            ret.insert(participant.id, participant);
+        }
+        Ok(ret)
+    }
+}
+
+impl_vec!(Participant);

src/consensus2/state.rs

@@ -0,0 +1,584 @@
+// TODO: Pending participants can also be a map?
+
+use std::{
+    collections::BTreeMap,
+    hash::{Hash, Hasher},
+    sync::{Arc, RwLock},
+    time::Duration,
+};
+
+use chrono::{NaiveDateTime, Utc};
+use fxhash::FxHasher;
+use log::{debug, error, warn};
+use rand::rngs::OsRng;
+
+use super::{
+    block::{Block, BlockProposal},
+    util::{get_current_time, Timestamp},
+    Metadata, Participant, ProposalChain, StreamletMetadata, Tx, Vote,
+};
+use crate::{
+    blockchain2::Blockchain,
+    crypto::{
+        keypair::{PublicKey, SecretKey},
+        schnorr::{SchnorrPublic, SchnorrSecret},
+    },
+    util::serial::{serialize, Encodable},
+    Result,
+};
+
+const DELTA: u64 = 60;
+
+/// This struct represents the information required by the consensus algorithm
+#[derive(Debug)]
+pub struct ConsensusState {
+    /// Genesis block creation timestamp
+    pub genesis_ts: Timestamp,
+    /// Genesis block
+    pub genesis_block: blake3::Hash,
+    /// Last finalized block hash,
+    pub last_block: blake3::Hash,
+    /// Last finalized block slot,
+    pub last_sl: u64,
+    /// Fork chains containing block proposals
+    pub proposals: Vec<ProposalChain>,
+    /// Orphan votes pool, in case a vote reaches a node before the
+    /// corresponding block
+    pub orphan_votes: Vec<Vote>,
+    /// Validators currently participating in the consensus
+    pub participants: BTreeMap<u64, Participant>,
+    /// Validators to be added on the next epoch as participants
+    pub pending_participants: Vec<Participant>,
+}
+
+impl ConsensusState {
+    pub fn new(genesis_ts: Timestamp, genesis_data: blake3::Hash) -> Result<Self> {
+        let genesis_block =
+            blake3::hash(&serialize(&Block::genesis_block(genesis_ts, genesis_data)));
+
+        Ok(Self {
+            genesis_ts,
+            genesis_block,
+            last_block: genesis_block,
+            last_sl: 0,
+            proposals: vec![],
+            orphan_votes: vec![],
+            participants: BTreeMap::new(),
+            pending_participants: vec![],
+        })
+    }
+}
+
+/// Atomic pointer to validator state.
+pub type ValidatorStatePtr = Arc<RwLock<ValidatorState>>;
+
+/// This struct represents the state of a validator node.
+pub struct ValidatorState {
+    /// Validator ID
+    pub id: u64,
+    /// Secret key, to sign messages
+    pub secret: SecretKey,
+    /// Validator public key
+    pub public: PublicKey,
+    /// Hot/Live data used by the consensus algorithm
+    pub consensus: ConsensusState,
+    /// Canonical (finalized) blockchain
+    pub blockchain: Blockchain,
+    /// Pending transactions
+    pub unconfirmed_txs: Vec<Tx>,
+}
+
+impl ValidatorState {
+    // TODO: Clock sync
+    // TODO: ID shouldn't be done like this
+    pub fn new(
+        db: &sled::Db, // <-- TODO: Avoid this with some wrapping, sled should only be in blockchain2
+        id: u64,
+        genesis_ts: Timestamp,
+        genesis_data: blake3::Hash,
+    ) -> Result<ValidatorStatePtr> {
+        let secret = SecretKey::random(&mut OsRng);
+        let public = PublicKey::from_secret(secret);
+        let consensus = ConsensusState::new(genesis_ts, genesis_data)?;
+        let blockchain = Blockchain::new(db, genesis_ts, genesis_data)?;
+        let unconfirmed_txs = vec![];
+
+        // TODO: Maybe async rwlock?
+        let state = Arc::new(RwLock::new(ValidatorState {
+            id,
+            secret,
+            public,
+            consensus,
+            blockchain,
+            unconfirmed_txs,
+        }));
+
+        Ok(state)
+    }
+
+    /// The node retrieves a transaction and appends it to the unconfirmed
+    /// transactions list. Additional validity rules must be defined by the
+    /// protocol for transactions.
+    pub fn append_tx(&mut self, tx: Tx) -> bool {
+        if self.unconfirmed_txs.contains(&tx) {
+            warn!("consensus::state::append_tx(): We already have this tx");
+            return false
+        }
+
+        self.unconfirmed_txs.push(tx);
+        true
+    }
+
+    /// Calculates current epoch, based on elapsed time from the genesis block.
+    /// Epoch duration is configured using the `DELTA` value.
+    pub fn current_epoch(&self) -> u64 {
+        self.consensus.genesis_ts.elapsed() / (2 * DELTA)
+    }
+
+    /// Calculates seconds until next epoch starting time.
+    /// Epochs durationis configured using the delta value.
+    pub fn next_epoch_start(&self) -> Duration {
+        let start_time = NaiveDateTime::from_timestamp(self.consensus.genesis_ts.0, 0);
+        let current_epoch = self.current_epoch() + 1;
+        let next_epoch_start = (current_epoch * (2 * DELTA)) + (start_time.timestamp() as u64);
+        let next_epoch_start = NaiveDateTime::from_timestamp(next_epoch_start as i64, 0);
+        let current_time = NaiveDateTime::from_timestamp(Utc::now().timestamp(), 0);
+        let diff = next_epoch_start - current_time;
+
+        Duration::new(diff.num_seconds().try_into().unwrap(), 0)
+    }
+
+    /// Find epoch leader, using a simple hash method.
+    /// Leader calculation is based on how many nodes are participating
+    /// in the network.
+    pub fn epoch_leader(&mut self) -> u64 {
+        let epoch = self.current_epoch();
+        let mut hasher = FxHasher::default();
+        epoch.hash(&mut hasher);
+        self.zero_participants_check();
+        let pos = hasher.finish() % (self.consensus.participants.len() as u64);
+        self.consensus.participants.iter().nth(pos as usize).unwrap().1.id
+    }
+
+    /// Check if we're the current epoch leader
+    pub fn is_epoch_leader(&mut self) -> bool {
+        self.id == self.epoch_leader()
+    }
+
+    /// Generate a block proposal for the current epoch, containing all
+    /// unconfirmed transactions. Proposal extends the longest notarized fork
+    /// chain the node is holding.
+    pub fn propose(&self) -> Result<Option<BlockProposal>> {
+        let epoch = self.current_epoch();
+        let prev_hash = self.longest_notarized_chain_last_hash().unwrap();
+        let unproposed_txs = self.unproposed_txs();
+
+        let metadata = Metadata::new(
+            get_current_time(),
+            String::from("proof"),
+            String::from("r"),
+            String::from("s"),
+        );
+
+        let sm = StreamletMetadata::new(self.consensus.participants.values().cloned().collect());
+
+        let signed_block = self.secret.sign(
+            &BlockProposal::to_proposal_hash(prev_hash, epoch, &unproposed_txs, &metadata)
+                .as_bytes()[..],
+        );
+
+        Ok(Some(BlockProposal::new(
+            self.public,
+            signed_block,
+            self.id,
+            prev_hash,
+            epoch,
+            unproposed_txs,
+            metadata,
+            sm,
+        )))
+    }
+
+    /// Retrieve all unconfirmed transactions not proposed in previous blocks.
+    pub fn unproposed_txs(&self) -> Vec<Tx> {
+        let mut unproposed_txs = self.unconfirmed_txs.clone();
+        for chain in &self.consensus.proposals {
+            for proposal in &chain.proposals {
+                for tx in &proposal.txs {
+                    if let Some(pos) = unproposed_txs.iter().position(|txs| *txs == *tx) {
+                        unproposed_txs.remove(pos);
+                    }
+                }
+            }
+        }
+
+        unproposed_txs
+    }
+
+    /// Finds the longest fully notarized blockchain the node holds and
+    /// returns the last block hash.
+    pub fn longest_notarized_chain_last_hash(&self) -> Result<blake3::Hash> {
+        let hash = if !self.consensus.proposals.is_empty() {
+            let mut longest_notarized_chain = &self.consensus.proposals[0];
+            let mut length = longest_notarized_chain.proposals.len();
+            if self.consensus.proposals.len() > 1 {
+                for chain in &self.consensus.proposals[1..] {
+                    if chain.notarized() && chain.proposals.len() > length {
+                        length = chain.proposals.len();
+                        longest_notarized_chain = chain;
+                    }
+                }
+            }
+
+            longest_notarized_chain.proposals.last().unwrap().hash()
+        } else {
+            self.consensus.last_block
+        };
+
+        Ok(hash)
+    }
+
+    /// Receive the proposed block, verify its sender (epoch leader),
+    /// and proceed with voting on it.
+    pub fn receive_proposal(&mut self, proposal: &BlockProposal) -> Result<Option<Vote>> {
+        let leader = self.epoch_leader();
+        if leader != proposal.id {
+            warn!(
+                "Received proposal not from epoch leader ({}), but from ({})",
+                leader, proposal.id
+            );
+            return Ok(None)
+        }
+
+        if !proposal.public_key.verify(
+            BlockProposal::to_proposal_hash(
+                proposal.st,
+                proposal.sl,
+                &proposal.txs,
+                &proposal.metadata,
+            )
+            .as_bytes(),
+            &proposal.signature,
+        ) {
+            warn!("Proposer ({}) signature could not be verified", proposal.id);
+            return Ok(None)
+        }
+
+        self.vote(proposal)
+    }
+
+    /// Given a proposal, the node finds which blockchain it extends.
+    /// If the proposal extends the canonical blockchain, a new fork chain
+    // is created. The node votes on the proposal only if it extends the
+    /// longest notarized fork chain it has seen.
+    pub fn vote(&mut self, proposal: &BlockProposal) -> Result<Option<Vote>> {
+        self.zero_participants_check();
+        let mut proposal = proposal.clone();
+
+        // Generate proposal hash
+        let proposal_hash = proposal.hash();
+
+        // Add orphan votes
+        let mut orphans = Vec::new();
+        for vote in self.consensus.orphan_votes.iter() {
+            if vote.proposal == proposal_hash {
+                proposal.sm.votes.push(vote.clone());
+                orphans.push(vote.clone());
+            }
+        }
+
+        for vote in orphans {
+            self.consensus.orphan_votes.retain(|v| *v != vote);
+        }
+
+        let index = self.find_extended_chain_index(&proposal)?;
+
+        if index == -2 {
+            return Ok(None)
+        }
+
+        let chain = match index {
+            -1 => {
+                let pc = ProposalChain::new(self.consensus.genesis_block, proposal.clone());
+                self.consensus.proposals.push(pc);
+                self.consensus.proposals.last().unwrap()
+            }
+            _ => {
+                self.consensus.proposals[index as usize].add(&proposal);
+                &self.consensus.proposals[index as usize]
+            }
+        };
+
+        if !self.extends_notarized_chain(chain) {
+            return Ok(None)
+        }
+
+        let signed_hash = self.secret.sign(&serialize(&proposal_hash));
+        Ok(Some(Vote::new(self.public, signed_hash, proposal_hash, proposal.sl, self.id)))
+    }
+
+    /// Verify if the provided chain is notarized excluding the last block.
+    pub fn extends_notarized_chain(&self, chain: &ProposalChain) -> bool {
+        for proposal in &chain.proposals[..(chain.proposals.len() - 1)] {
+            if !proposal.sm.notarized {
+                return false
+            }
+        }
+
+        true
+    }
+
+    /// Given a proposal, find the index of the chain it extends.
+    pub fn find_extended_chain_index(&self, proposal: &BlockProposal) -> Result<i64> {
+        for (index, chain) in self.consensus.proposals.iter().enumerate() {
+            let last = chain.proposals.last().unwrap();
+            let hash = last.hash();
+            if proposal.st == hash && proposal.sl > last.sl {
+                return Ok(index as i64)
+            }
+
+            if proposal.st == last.st && proposal.sl == last.sl {
+                warn!("Proposal already received");
+                return Ok(-2)
+            }
+        }
+
+        if proposal.st != self.consensus.last_block || proposal.sl <= self.consensus.last_sl {
+            warn!("Proposal doesn't extend any known chain");
+            return Ok(-2)
+        }
+
+        Ok(-1)
+    }
+
+    /// Receive a vote for a proposal.
+    /// First, sender is verified using their public key.
+    /// The proposal is then searched for in the node's fork chains.
+    /// If the vote wasn't received before, it is appended to the proposal
+    /// votes list.
+    /// When a node sees 2n/3 votes for a proposal, it notarizes it.
+    /// When a proposal gets notarized, the transactions it contains are
+    /// removed from the node's unconfirmed tx list.
+    /// Finally, we check if the notarization of the proposal can finalize
+    /// parent proposals in its chain.
+    pub fn receive_vote(&mut self, vote: &Vote) -> Result<bool> {
+        let mut encoded_proposal = vec![];
+
+        let result = vote.proposal.encode(&mut encoded_proposal);
+        match result {
+            Ok(_) => (),
+            Err(e) => {
+                error!("Proposal encoding failed: {:?}", e);
+                return Ok(false)
+            }
+        };
+
+        if !vote.public_key.verify(&encoded_proposal, &vote.vote) {
+            warn!("Voter ({}), signature couldn't be verified", vote.id);
+            return Ok(false)
+        }
+
+        let node_count = self.consensus.participants.len();
+        self.zero_participants_check();
+
+        // Checking that the voter can actually vote.
+        match self.consensus.participants.get(&vote.id) {
+            Some(participant) => {
+                if self.current_epoch() <= participant.joined {
+                    warn!("Voter ({}) joined after current epoch.", vote.id);
+                    return Ok(false)
+                }
+            }
+            None => {
+                warn!("Voter ({}) is not a participant!", vote.id);
+                return Ok(false)
+            }
+        }
+
+        let proposal = self.find_proposal(&vote.proposal)?;
+        if proposal.is_none() {
+            warn!("Received vote for unknown proposal.");
+            if !self.consensus.orphan_votes.contains(vote) {
+                self.consensus.orphan_votes.push(vote.clone());
+            }
+
+            return Ok(false)
+        }
+
+        let (proposal, chain_idx) = proposal.unwrap();
+        if proposal.sm.votes.contains(vote) {
+            return Ok(false)
+        }
+
+        proposal.sm.votes.push(vote.clone());
+
+        if !proposal.sm.notarized && proposal.sm.votes.len() > (2 * node_count / 3) {
+            debug!("Notarized a block");
+            proposal.sm.notarized = true;
+            self.chain_finalization(chain_idx)?;
+        }
+
+        // Updating participant vote
+        let mut participant = match self.consensus.participants.get(&vote.id) {
+            Some(p) => p.clone(),
+            None => Participant::new(vote.id, vote.sl),
+        };
+
+        match participant.voted {
+            Some(voted) => {
+                if vote.sl > voted {
+                    participant.voted = Some(vote.sl);
+                }
+            }
+            None => participant.voted = Some(vote.sl),
+        }
+
+        self.consensus.participants.insert(participant.id, participant);
+        Ok(true)
+    }
+
+    /// Search the chains we're holding for the given proposal.
+    pub fn find_proposal(
+        &mut self,
+        vote_proposal: &blake3::Hash,
+    ) -> Result<Option<(&mut BlockProposal, i64)>> {
+        for (index, chain) in &mut self.consensus.proposals.iter_mut().enumerate() {
+            for proposal in chain.proposals.iter_mut().rev() {
+                let proposal_hash = proposal.hash();
+                if vote_proposal == &proposal_hash {
+                    return Ok(Some((proposal, index as i64)))
+                }
+            }
+        }
+
+        Ok(None)
+    }
+
+    /// Provided an index, the node checks if the chain can be finalized.
+    /// Consensus finalization logic:
+    /// - If the node has observed the notarization of 3 consecutive
+    ///   proposals in a fork chain, it finalizes (appends to canonical
+    ///   blockchain) all proposals up to the middle block.
+    /// When fork chain proposals are finalized, the rest of fork chains not
+    /// starting by those proposals are removed.
+    pub fn chain_finalization(&mut self, chain_index: i64) -> Result<()> {
+        let chain = &mut self.consensus.proposals[chain_index as usize];
+        let len = chain.proposals.len();
+        if len < 3 {
+            return Ok(())
+        }
+
+        let mut consecutive = 0;
+        for proposal in &chain.proposals {
+            if proposal.sm.notarized {
+                consecutive += 1;
+                continue
+            }
+
+            break
+        }
+
+        if consecutive < 3 {
+            return Ok(())
+        }
+
+        let mut finalized = vec![];
+        for proposal in &mut chain.proposals[..(consecutive - 1)] {
+            proposal.sm.finalized = true;
+            finalized.push(proposal.clone());
+            for tx in proposal.txs.clone() {
+                if let Some(pos) = self.unconfirmed_txs.iter().position(|txs| *txs == tx) {
+                    self.unconfirmed_txs.remove(pos);
+                }
+            }
+        }
+
+        chain.proposals.drain(0..(consecutive - 1));
+
+        // Append to canonical chain
+        let blockhashes = self.blockchain.add(&finalized)?;
+        self.consensus.last_block = *blockhashes.last().unwrap();
+        self.consensus.last_sl = finalized.last().unwrap().sl;
+
+        let mut dropped = vec![];
+        for chain in self.consensus.proposals.iter() {
+            let first = chain.proposals.first().unwrap();
+            if first.st != self.consensus.last_block || first.sl <= self.consensus.last_sl {
+                dropped.push(chain.clone());
+            }
+        }
+
+        for chain in dropped {
+            self.consensus.proposals.retain(|c| *c != chain);
+        }
+
+        // Remove orphan votes
+        let mut orphans = vec![];
+        for vote in self.consensus.orphan_votes.iter() {
+            if vote.sl <= self.consensus.last_sl {
+                orphans.push(vote.clone());
+            }
+        }
+
+        for vote in orphans {
+            self.consensus.orphan_votes.retain(|v| *v != vote);
+        }
+
+        Ok(())
+    }
+
+    /// Append a new participant to the pending participants list.
+    pub fn append_participant(&mut self, participant: Participant) -> bool {
+        if self.consensus.pending_participants.contains(&participant) {
+            return false
+        }
+
+        self.consensus.pending_participants.push(participant);
+        true
+    }
+
+    /// Prevent the extreme case scenario where network is initialized, but
+    /// some nodes have not pushed the initial participants in the map.
+    pub fn zero_participants_check(&mut self) {
+        if self.consensus.participants.is_empty() {
+            for participant in &self.consensus.pending_participants {
+                self.consensus.participants.insert(participant.id, participant.clone());
+            }
+
+            self.consensus.pending_participants = Vec::new();
+        }
+    }
+
+    /// Refresh the participants map, to retain only the active ones.
+    /// Active nodes are considered those who joined or voted on a previous epoch.
+    pub fn refresh_participants(&mut self) {
+        // Adding pending participants
+        for participant in &self.consensus.pending_participants {
+            self.consensus.participants.insert(participant.id, participant.clone());
+        }
+
+        self.consensus.pending_participants = vec![];
+
+        let mut inactive = Vec::new();
+        let previous_epoch = self.current_epoch() - 1;
+        for (index, participant) in self.consensus.participants.clone().iter() {
+            match participant.voted {
+                Some(epoch) => {
+                    if epoch < previous_epoch {
+                        inactive.push(*index);
+                    }
+                }
+
+                None => {
+                    if participant.joined < previous_epoch {
+                        inactive.push(*index);
+                    }
+                }
+            }
+        }
+
+        for index in inactive {
+            self.consensus.participants.remove(&index);
+        }
+    }
+}

src/consensus2/tx.rs

@@ -0,0 +1,21 @@
+use std::io;
+
+use crate::{
+    impl_vec, net,
+    util::serial::{Decodable, Encodable, SerialDecodable, SerialEncodable, VarInt},
+    Result,
+};
+
+/// Temporary transaction representation.
+#[derive(Debug, Clone, PartialEq, SerialEncodable, SerialDecodable)]
+pub struct Tx {
+    pub payload: String,
+}
+
+impl net::Message for Tx {
+    fn name() -> &'static str {
+        "tx"
+    }
+}
+
+impl_vec!(Tx);

src/consensus2/util.rs

@@ -0,0 +1,22 @@
+use chrono::{NaiveDateTime, Utc};
+
+use crate::util::serial::{SerialDecodable, SerialEncodable};
+
+/// Wrapper struct to represent [`chrono`] UTC timestamps.
+#[derive(Debug, Copy, Clone, PartialEq, SerialDecodable, SerialEncodable)]
+pub struct Timestamp(pub i64);
+
+impl Timestamp {
+    /// Calculates elapsed time of a `Timestamp`.
+    pub fn elapsed(&self) -> u64 {
+        let start_time = NaiveDateTime::from_timestamp(self.0, 0);
+        let end_time = NaiveDateTime::from_timestamp(Utc::now().timestamp(), 0);
+        let diff = end_time - start_time;
+        diff.num_seconds() as u64
+    }
+}
+
+/// Generate a [`Timestamp`] of the current time.
+pub fn get_current_time() -> Timestamp {
+    Timestamp(Utc::now().timestamp())
+}

src/consensus2/vote.rs

@@ -0,0 +1,43 @@
+use std::io;
+
+use crate::{
+    crypto::{keypair::PublicKey, schnorr::Signature},
+    impl_vec, net,
+    util::serial::{Decodable, Encodable, SerialDecodable, SerialEncodable, VarInt},
+    Result,
+};
+
+/// This struct represents a `Vote` used by the Streamlet consensus
+#[derive(Debug, Clone, PartialEq, SerialDecodable, SerialEncodable)]
+pub struct Vote {
+    /// Node public key
+    pub public_key: PublicKey,
+    /// Block signature
+    pub vote: Signature,
+    /// Block proposal hash to vote on
+    pub proposal: blake3::Hash,
+    /// Slot uid, generated by the beacon
+    pub sl: u64,
+    /// Node ID
+    pub id: u64,
+}
+
+impl Vote {
+    pub fn new(
+        public_key: PublicKey,
+        vote: Signature,
+        proposal: blake3::Hash,
+        sl: u64,
+        id: u64,
+    ) -> Self {
+        Self { public_key, vote, proposal, sl, id }
+    }
+}
+
+impl net::Message for Vote {
+    fn name() -> &'static str {
+        "vote"
+    }
+}
+
+impl_vec!(Vote);

src/lib.rs

@@ -10,6 +10,9 @@ pub mod blockchain2;
 #[cfg(feature = "blockchain")]
 pub mod consensus;
 
+#[cfg(feature = "blockchain2")]
+pub mod consensus2;
+
 #[cfg(feature = "wasm-runtime")]
 pub mod runtime;