diff --git a/coordinator/tributary/Cargo.toml b/coordinator/tributary/Cargo.toml
index 6ca0da73..89b87634 100644
--- a/coordinator/tributary/Cargo.toml
+++ b/coordinator/tributary/Cargo.toml
@@ -12,8 +12,10 @@ async-trait = "0.1"
 thiserror = "1"
 
 subtle = "^2"
-zeroize = { version = "^1.5", optional = true }
-rand_core = { version = "0.6", optional = true }
+zeroize = "^1.5"
+
+rand = "0.8"
+rand_chacha = "0.3"
 
 blake2 = "0.10"
 transcript = { package = "flexible-transcript", path = "../../crypto/transcript", features = ["recommended"] }
@@ -25,6 +27,7 @@ hex = "0.4"
 log = "0.4"
 
 scale = { package = "parity-scale-codec", version = "3", features = ["derive"] }
+futures = "0.3"
 tendermint = { package = "tendermint-machine", path = "./tendermint" }
 
 tokio = { version = "1", features = ["macros", "sync", "time", "rt"] }
@@ -34,4 +37,4 @@ zeroize = "^1.5"
 rand_core = "0.6"
 
 [features]
-tests = ["zeroize", "rand_core"]
+tests = []
diff --git a/coordinator/tributary/src/blockchain.rs b/coordinator/tributary/src/blockchain.rs
index 93517de1..7a44904f 100644
--- a/coordinator/tributary/src/blockchain.rs
+++ b/coordinator/tributary/src/blockchain.rs
@@ -8,6 +8,7 @@ use crate::{Signed, TransactionKind, Transaction, ProvidedTransactions, BlockErr
 pub struct Blockchain<T: Transaction> {
   genesis: [u8; 32],
   // TODO: db
+  block_number: u64,
   tip: [u8; 32],
   next_nonces: HashMap<<Ristretto as Ciphersuite>::G, u32>,
 
@@ -17,7 +18,7 @@ pub struct Blockchain<T: Transaction> {
 
 impl<T: Transaction> Blockchain<T> {
   pub fn new(genesis: [u8; 32], participants: &[<Ristretto as Ciphersuite>::G]) -> Self {
-    // TODO: Reload next_nonces/provided/mempool
+    // TODO: Reload block_number/tip/next_nonces/provided/mempool
 
     let mut next_nonces = HashMap::new();
     for participant in participants {
@@ -27,6 +28,7 @@ impl<T: Transaction> Blockchain<T> {
     Self {
       genesis,
 
+      block_number: 0,
       tip: genesis,
       next_nonces,
 
@@ -39,6 +41,10 @@ impl<T: Transaction> Blockchain<T> {
     self.tip
   }
 
+  pub fn block_number(&self) -> u64 {
+    self.block_number
+  }
+
   pub fn add_transaction(&mut self, tx: T) -> bool {
     self.mempool.add(&self.next_nonces, tx)
   }
@@ -73,6 +79,7 @@ impl<T: Transaction> Blockchain<T> {
 
     // None of the following assertions should be reachable since we verified the block
     self.tip = block.hash();
+    self.block_number += 1;
     for tx in &block.transactions {
       match tx.kind() {
         TransactionKind::Provided => {
diff --git a/coordinator/tributary/src/lib.rs b/coordinator/tributary/src/lib.rs
index 7fef0032..5563bc35 100644
--- a/coordinator/tributary/src/lib.rs
+++ b/coordinator/tributary/src/lib.rs
@@ -1,4 +1,23 @@
-use std::io;
+use core::fmt::Debug;
+use std::{
+  sync::{Arc, RwLock},
+  io,
+  collections::HashMap,
+};
+
+use async_trait::async_trait;
+
+use zeroize::Zeroizing;
+
+use ciphersuite::{Ciphersuite, Ristretto};
+
+use scale::Decode;
+use futures::SinkExt;
+use ::tendermint::{
+  ext::{BlockNumber, Commit, Block as BlockTrait, Network as NetworkTrait},
+  SignedMessageFor, SyncedBlock, SyncedBlockSender, MessageSender, TendermintMachine,
+  TendermintHandle,
+};
 
 mod merkle;
 pub(crate) use merkle::*;
@@ -19,11 +38,14 @@ mod mempool;
 pub use mempool::*;
 
 mod tendermint;
-pub use crate::tendermint::*;
+pub(crate) use crate::tendermint::*;
 
 #[cfg(any(test, feature = "tests"))]
 pub mod tests;
 
+pub(crate) const TRANSACTION_MESSAGE: u8 = 0;
+pub(crate) const TENDERMINT_MESSAGE: u8 = 1;
+
 /// An item which can be read and written.
 pub trait ReadWrite: Sized {
   fn read<R: io::Read>(reader: &mut R) -> io::Result<Self>;
@@ -36,3 +58,128 @@ pub trait ReadWrite: Sized {
     buf
   }
 }
+
+#[async_trait]
+pub trait P2p: 'static + Send + Sync + Clone + Debug {
+  async fn broadcast(&self, msg: Vec<u8>);
+}
+
+#[async_trait]
+impl<P: P2p> P2p for Arc<P> {
+  async fn broadcast(&self, msg: Vec<u8>) {
+    (*self).broadcast(msg).await
+  }
+}
+
+pub struct Tributary<T: Transaction, P: P2p> {
+  network: Network<T, P>,
+
+  synced_block: SyncedBlockSender<Network<T, P>>,
+  messages: MessageSender<Network<T, P>>,
+}
+
+impl<T: Transaction, P: P2p> Tributary<T, P> {
+  pub async fn new(
+    genesis: [u8; 32],
+    start_time: u64,
+    key: Zeroizing<<Ristretto as Ciphersuite>::F>,
+    validators: HashMap<<Ristretto as Ciphersuite>::G, u64>,
+    p2p: P,
+  ) -> Self {
+    let validators_vec = validators.keys().cloned().collect::<Vec<_>>();
+
+    let signer = Arc::new(Signer::new(genesis, key));
+    let validators = Arc::new(Validators::new(genesis, validators));
+
+    let mut blockchain = Blockchain::new(genesis, &validators_vec);
+    let block_number = blockchain.block_number();
+    let start_time = start_time; // TODO: Get the start time from the blockchain
+    let proposal = TendermintBlock(blockchain.build_block().serialize());
+    let blockchain = Arc::new(RwLock::new(blockchain));
+
+    let network = Network { genesis, signer, validators, blockchain, p2p };
+
+    // The genesis block is 0, so we're working on block #1
+    let block_number = BlockNumber(block_number + 1);
+    let TendermintHandle { synced_block, messages, machine } =
+      TendermintMachine::new(network.clone(), block_number, start_time, proposal).await;
+    tokio::task::spawn(machine.run());
+
+    Self { network, synced_block, messages }
+  }
+
+  pub fn provide_transaction(&self, tx: T) {
+    self.network.blockchain.write().unwrap().provide_transaction(tx)
+  }
+
+  // Returns if the transaction was valid.
+  pub async fn add_transaction(&self, tx: T) -> bool {
+    let mut to_broadcast = vec![TRANSACTION_MESSAGE];
+    tx.write(&mut to_broadcast).unwrap();
+    let res = self.network.blockchain.write().unwrap().add_transaction(tx);
+    if res {
+      self.network.p2p.broadcast(to_broadcast).await;
+    }
+    res
+  }
+
+  // Sync a block.
+  // TODO: Since we have a static validator set, we should only need the tail commit?
+  pub async fn sync_block(&mut self, block: Block<T>, commit: Vec<u8>) -> bool {
+    let (tip, block_number) = {
+      let blockchain = self.network.blockchain.read().unwrap();
+      (blockchain.tip(), blockchain.block_number())
+    };
+
+    if block.header.parent != tip {
+      return false;
+    }
+
+    let block = TendermintBlock(block.serialize());
+    let Ok(commit) = Commit::<Arc<Validators>>::decode(&mut commit.as_ref()) else {
+      return false;
+    };
+    if !self.network.verify_commit(block.id(), &commit) {
+      return false;
+    }
+
+    let number = BlockNumber(block_number + 1);
+    self.synced_block.send(SyncedBlock { number, block, commit }).await.unwrap();
+    true
+  }
+
+  // Return true if the message should be rebroadcasted.
+  pub async fn handle_message(&mut self, msg: Vec<u8>) -> bool {
+    match msg[0] {
+      TRANSACTION_MESSAGE => {
+        let Ok(tx) = T::read::<&[u8]>(&mut &msg[1 ..]) else {
+          return false;
+        };
+
+        // TODO: Sync mempools with fellow peers
+        // Can we just rebroadcast transactions not included for at least two blocks?
+        self.network.blockchain.write().unwrap().add_transaction(tx)
+      }
+
+      TENDERMINT_MESSAGE => {
+        let Ok(msg) = SignedMessageFor::<Network<T, P>>::decode::<&[u8]>(&mut &msg[1 ..]) else {
+          return false;
+        };
+
+        // If this message isn't to form consensus on the next block, ignore it
+        if msg.block().0 != (self.network.blockchain.read().unwrap().block_number() + 1) {
+          return false;
+        }
+
+        if !msg.verify_signature(&self.network.validators) {
+          return false;
+        }
+
+        self.messages.send(msg).await.unwrap();
+        true
+      }
+
+      _ => false,
+    }
+  }
+}
diff --git a/coordinator/tributary/src/tendermint.rs b/coordinator/tributary/src/tendermint.rs
index 919df6c7..99b48fb1 100644
--- a/coordinator/tributary/src/tendermint.rs
+++ b/coordinator/tributary/src/tendermint.rs
@@ -1,11 +1,17 @@
 use core::ops::Deref;
-use std::{sync::Arc, collections::HashMap};
+use std::{
+  sync::{Arc, RwLock},
+  collections::HashMap,
+};
 
 use async_trait::async_trait;
 
 use subtle::ConstantTimeEq;
 use zeroize::{Zeroize, Zeroizing};
 
+use rand::{SeedableRng, seq::SliceRandom};
+use rand_chacha::ChaCha12Rng;
+
 use transcript::{Transcript, RecommendedTranscript};
 
 use ciphersuite::{
@@ -28,7 +34,10 @@ use tendermint::{
 
 use tokio::time::{Duration, sleep};
 
-use crate::{ReadWrite, Transaction, TransactionError, BlockHeader, Block, BlockError, Blockchain};
+use crate::{
+  TENDERMINT_MESSAGE, ReadWrite, Transaction, TransactionError, BlockHeader, Block, BlockError,
+  Blockchain, P2p,
+};
 
 fn challenge(
   genesis: [u8; 32],
@@ -46,11 +55,17 @@ fn challenge(
 }
 
 #[derive(Clone, PartialEq, Eq, Debug)]
-struct Signer {
+pub(crate) struct Signer {
   genesis: [u8; 32],
   key: Zeroizing<<Ristretto as Ciphersuite>::F>,
 }
 
+impl Signer {
+  pub(crate) fn new(genesis: [u8; 32], key: Zeroizing<<Ristretto as Ciphersuite>::F>) -> Signer {
+    Signer { genesis, key }
+  }
+}
+
 #[async_trait]
 impl SignerTrait for Signer {
   type ValidatorId = [u8; 32];
@@ -99,13 +114,40 @@ impl SignerTrait for Signer {
 }
 
 #[derive(Clone, PartialEq, Eq, Debug)]
-struct Validators {
+pub(crate) struct Validators {
   genesis: [u8; 32],
-  weight: u64,
+  total_weight: u64,
   weights: HashMap<[u8; 32], u64>,
   robin: Vec<[u8; 32]>,
 }
 
+impl Validators {
+  pub(crate) fn new(
+    genesis: [u8; 32],
+    validators: HashMap<<Ristretto as Ciphersuite>::G, u64>,
+  ) -> Validators {
+    let mut total_weight = 0;
+    let mut weights = HashMap::new();
+
+    let mut transcript = RecommendedTranscript::new(b"Round Robin Randomization");
+    let mut robin = vec![];
+    for (validator, weight) in validators {
+      let validator = validator.to_bytes();
+      // TODO: Make an error out of this
+      assert!(weight != 0);
+      total_weight += weight;
+      weights.insert(validator, weight);
+
+      transcript.append_message(b"validator", validator);
+      transcript.append_message(b"weight", weight.to_le_bytes());
+      robin.extend(vec![validator; usize::try_from(weight).unwrap()]);
+    }
+    robin.shuffle(&mut ChaCha12Rng::from_seed(transcript.rng_seed(b"robin")));
+
+    Validators { genesis, total_weight, weights, robin }
+  }
+}
+
 impl SignatureScheme for Validators {
   type ValidatorId = [u8; 32];
   type Signature = [u8; 64];
@@ -151,7 +193,7 @@ impl Weights for Validators {
   type ValidatorId = [u8; 32];
 
   fn total_weight(&self) -> u64 {
-    self.weight
+    self.total_weight
   }
   fn weight(&self, validator: Self::ValidatorId) -> u64 {
     self.weights[&validator]
@@ -170,7 +212,7 @@ impl Weights for Validators {
 }
 
 #[derive(Clone, PartialEq, Eq, Debug, Encode, Decode)]
-struct TendermintBlock(Vec<u8>);
+pub(crate) struct TendermintBlock(pub Vec<u8>);
 impl BlockTrait for TendermintBlock {
   type Id = [u8; 32];
   fn id(&self) -> Self::Id {
@@ -178,16 +220,17 @@ impl BlockTrait for TendermintBlock {
   }
 }
 
-#[derive(Clone, PartialEq, Eq, Debug)]
-struct Network<T: Transaction> {
-  genesis: [u8; 32],
-  signer: Arc<Signer>,
-  validators: Arc<Validators>,
-  blockchain: Blockchain<T>,
+#[derive(Clone, Debug)]
+pub(crate) struct Network<T: Transaction, P: P2p> {
+  pub(crate) genesis: [u8; 32],
+  pub(crate) signer: Arc<Signer>,
+  pub(crate) validators: Arc<Validators>,
+  pub(crate) blockchain: Arc<RwLock<Blockchain<T>>>,
+  pub(crate) p2p: P,
 }
 
 #[async_trait]
-impl<T: Transaction> NetworkTrait for Network<T> {
+impl<T: Transaction, P: P2p> NetworkTrait for Network<T, P> {
   type ValidatorId = [u8; 32];
   type SignatureScheme = Arc<Validators>;
   type Weights = Arc<Validators>;
@@ -206,12 +249,14 @@ impl<T: Transaction> NetworkTrait for Network<T> {
     self.validators.clone()
   }
 
-  async fn broadcast(&mut self, _msg: SignedMessageFor<Self>) {
-    todo!()
+  async fn broadcast(&mut self, msg: SignedMessageFor<Self>) {
+    let mut to_broadcast = vec![TENDERMINT_MESSAGE];
+    to_broadcast.extend(msg.encode());
+    self.p2p.broadcast(to_broadcast).await
   }
   async fn slash(&mut self, validator: Self::ValidatorId) {
     log::error!(
-      "validator {} was slashed on tributary {}",
+      "validator {} triggered a slash event on tributary {}",
       hex::encode(validator),
       hex::encode(self.genesis)
     );
@@ -220,7 +265,7 @@ impl<T: Transaction> NetworkTrait for Network<T> {
   async fn validate(&mut self, block: &Self::Block) -> Result<(), TendermintBlockError> {
     let block =
       Block::read::<&[u8]>(&mut block.0.as_ref()).map_err(|_| TendermintBlockError::Fatal)?;
-    self.blockchain.verify_block(&block).map_err(|e| match e {
+    self.blockchain.read().unwrap().verify_block(&block).map_err(|e| match e {
       BlockError::TransactionError(TransactionError::MissingProvided(_)) => {
         TendermintBlockError::Temporal
       }
@@ -231,7 +276,7 @@ impl<T: Transaction> NetworkTrait for Network<T> {
   async fn add_block(
     &mut self,
     block: Self::Block,
-    _commit: Commit<Self::SignatureScheme>,
+    commit: Commit<Self::SignatureScheme>,
   ) -> Option<Self::Block> {
     let invalid_block = || {
       // There's a fatal flaw in the code, it's behind a hard fork, or the validators turned
@@ -242,12 +287,15 @@ impl<T: Transaction> NetworkTrait for Network<T> {
       panic!("validators added invalid block to tributary {}", hex::encode(self.genesis));
     };
 
+    assert!(self.verify_commit(block.id(), commit));
+
     let Ok(block) = Block::read::<&[u8]>(&mut block.0.as_ref()) else {
       return invalid_block();
     };
 
     loop {
-      match self.blockchain.add_block(&block) {
+      let block_res = self.blockchain.write().unwrap().add_block(&block);
+      match block_res {
         Ok(()) => break,
         Err(BlockError::TransactionError(TransactionError::MissingProvided(hash))) => {
           log::error!(
@@ -261,7 +309,8 @@ impl<T: Transaction> NetworkTrait for Network<T> {
       }
     }
 
-    // TODO: Handle the commit and return the next proposal
-    todo!()
+    // TODO: Save the commit to disk
+
+    Some(TendermintBlock(self.blockchain.write().unwrap().build_block().serialize()))
   }
 }
diff --git a/coordinator/tributary/src/tests/block.rs b/coordinator/tributary/src/tests/block.rs
index ba2fffd1..aa1c9c09 100644
--- a/coordinator/tributary/src/tests/block.rs
+++ b/coordinator/tributary/src/tests/block.rs
@@ -3,7 +3,7 @@ use std::{
   collections::{HashSet, HashMap},
 };
 
-use rand_core::{RngCore, OsRng};
+use rand::{RngCore, rngs::OsRng};
 
 use blake2::{Digest, Blake2s256};
 
diff --git a/coordinator/tributary/src/tests/blockchain.rs b/coordinator/tributary/src/tests/blockchain.rs
index 803d80d3..e027b00d 100644
--- a/coordinator/tributary/src/tests/blockchain.rs
+++ b/coordinator/tributary/src/tests/blockchain.rs
@@ -1,7 +1,7 @@
 use std::collections::{HashSet, HashMap};
 
 use zeroize::Zeroizing;
-use rand_core::{RngCore, OsRng};
+use rand::{RngCore, rngs::OsRng};
 
 use blake2::{Digest, Blake2s256};
 
@@ -24,6 +24,7 @@ fn new_blockchain<T: Transaction>(
 ) -> Blockchain<T> {
   let blockchain = Blockchain::new(genesis, participants);
   assert_eq!(blockchain.tip(), genesis);
+  assert_eq!(blockchain.block_number(), 0);
   blockchain
 }
 
@@ -37,6 +38,7 @@ fn block_addition() {
   blockchain.verify_block(&block).unwrap();
   assert!(blockchain.add_block(&block).is_ok());
   assert_eq!(blockchain.tip(), block.hash());
+  assert_eq!(blockchain.block_number(), 1);
 }
 
 #[test]
diff --git a/coordinator/tributary/src/tests/mempool.rs b/coordinator/tributary/src/tests/mempool.rs
index b9a68db8..cf569a9d 100644
--- a/coordinator/tributary/src/tests/mempool.rs
+++ b/coordinator/tributary/src/tests/mempool.rs
@@ -1,7 +1,7 @@
 use std::collections::HashMap;
 
 use zeroize::Zeroizing;
-use rand_core::{RngCore, OsRng};
+use rand::{RngCore, rngs::OsRng};
 
 use ciphersuite::{group::ff::Field, Ciphersuite, Ristretto};
 
diff --git a/coordinator/tributary/src/tests/merkle.rs b/coordinator/tributary/src/tests/merkle.rs
index c3b0e626..6c3ece22 100644
--- a/coordinator/tributary/src/tests/merkle.rs
+++ b/coordinator/tributary/src/tests/merkle.rs
@@ -1,6 +1,6 @@
 use std::collections::HashSet;
 
-use rand_core::{RngCore, OsRng};
+use rand::{RngCore, rngs::OsRng};
 
 #[test]
 fn merkle() {
diff --git a/coordinator/tributary/src/tests/transaction/mod.rs b/coordinator/tributary/src/tests/transaction/mod.rs
index 1ecafa55..14d2ab8d 100644
--- a/coordinator/tributary/src/tests/transaction/mod.rs
+++ b/coordinator/tributary/src/tests/transaction/mod.rs
@@ -4,7 +4,7 @@ use std::{
 };
 
 use zeroize::Zeroizing;
-use rand_core::{RngCore, CryptoRng};
+use rand::{RngCore, CryptoRng};
 
 use blake2::{Digest, Blake2s256};
 
diff --git a/coordinator/tributary/src/tests/transaction/provided.rs b/coordinator/tributary/src/tests/transaction/provided.rs
index 15538206..3a80359d 100644
--- a/coordinator/tributary/src/tests/transaction/provided.rs
+++ b/coordinator/tributary/src/tests/transaction/provided.rs
@@ -1,6 +1,6 @@
 use std::collections::{HashSet, HashMap};
 
-use rand_core::OsRng;
+use rand::rngs::OsRng;
 
 use crate::{Transaction, verify_transaction, tests::random_provided_transaction};
 
diff --git a/coordinator/tributary/src/tests/transaction/signed.rs b/coordinator/tributary/src/tests/transaction/signed.rs
index a6f301a6..8144cd6d 100644
--- a/coordinator/tributary/src/tests/transaction/signed.rs
+++ b/coordinator/tributary/src/tests/transaction/signed.rs
@@ -1,6 +1,6 @@
 use std::collections::{HashSet, HashMap};
 
-use rand_core::OsRng;
+use rand::rngs::OsRng;
 
 use blake2::{Digest, Blake2s256};
 
@@ -13,7 +13,7 @@ use crate::{
 
 #[test]
 fn serialize_signed() {
-  let signed = random_signed(&mut rand_core::OsRng);
+  let signed = random_signed(&mut rand::rngs::OsRng);
   assert_eq!(Signed::read::<&[u8]>(&mut signed.serialize().as_ref()).unwrap(), signed);
 }
 
diff --git a/coordinator/tributary/src/transaction.rs b/coordinator/tributary/src/transaction.rs
index c0fa48f3..53f265ce 100644
--- a/coordinator/tributary/src/transaction.rs
+++ b/coordinator/tributary/src/transaction.rs
@@ -73,7 +73,7 @@ pub enum TransactionKind<'a> {
   Signed(&'a Signed),
 }
 
-pub trait Transaction: Send + Sync + Clone + Eq + Debug + ReadWrite {
+pub trait Transaction: 'static + Send + Sync + Clone + Eq + Debug + ReadWrite {
   /// Return what type of transaction this is.
   fn kind(&self) -> TransactionKind<'_>;