Make t and allowed_delta configurable

crates/e2e-tests/src/e2e_flow.rs

@@ -1317,6 +1317,34 @@ mod tests {
         Ok(())
     }
 
+    #[tokio::test]
+    async fn test_mpc_config_defaults_match_rust() -> Result<()> {
+        init_test_logging();
+
+        let networks = TestNetworksBuilder::new().with_nodes(1).build().await?;
+        networks.hashi_network.nodes()[0]
+            .wait_for_mpc_key(Duration::from_secs(60))
+            .await?;
+
+        use hashi::onchain::types::DEFAULT_MPC_THRESHOLD_BASIS_POINTS;
+        use hashi::onchain::types::DEFAULT_MPC_WEIGHT_REDUCTION_ALLOWED_DELTA;
+
+        let hashi = networks.hashi_network.nodes()[0].hashi();
+        let threshold_bps = hashi.onchain_state().mpc_threshold_basis_points();
+        let weight_reduction_allowed_delta =
+            hashi.onchain_state().mpc_weight_reduction_allowed_delta();
+
+        assert_eq!(
+            threshold_bps, DEFAULT_MPC_THRESHOLD_BASIS_POINTS,
+            "on-chain mpc_threshold_basis_points ({threshold_bps}) != Rust default ({DEFAULT_MPC_THRESHOLD_BASIS_POINTS})"
+        );
+        assert_eq!(
+            weight_reduction_allowed_delta, DEFAULT_MPC_WEIGHT_REDUCTION_ALLOWED_DELTA,
+            "on-chain mpc_weight_reduction_allowed_delta ({weight_reduction_allowed_delta}) != Rust default ({DEFAULT_MPC_WEIGHT_REDUCTION_ALLOWED_DELTA})"
+        );
+        Ok(())
+    }
+
     /// Verify that a withdrawal can spend a change output whose producing
     /// transaction is mined on Bitcoin but not yet confirmed on Sui. The
     /// actual Bitcoin confirmation count must be queried from the node

crates/hashi/src/lib.rs

@@ -28,9 +28,6 @@ pub mod tls;
 pub mod utxo_pool;
 pub mod withdrawals;
 
-/// The allowed delta for weight reduction in basis points (800 means 8%).
-/// This matches Sui's `random_beacon_reduction_allowed_delta` configuration.
-const WEIGHT_REDUCTION_ALLOWED_DELTA: u16 = 800;
 // TODO: Tune based on production workload.
 const BATCH_SIZE_PER_WEIGHT: u16 = 10;
 
@@ -220,7 +217,10 @@ impl Hashi {
         protocol_type: mpc::types::ProtocolType,
     ) -> anyhow::Result<mpc::MpcManager> {
         let state = self.onchain_state().state();
-        let committee_set = &state.hashi().committees;
+        let hashi = state.hashi();
+        let committee_set = &hashi.committees;
+        let threshold_basis_points = hashi.config.mpc_threshold_basis_points();
+        let weight_reduction_allowed_delta = hashi.config.mpc_weight_reduction_allowed_delta();
         let session_id = mpc::SessionId::new(self.config.sui_chain_id(), epoch, &protocol_type);
         let encryption_key = self.config.encryption_private_key()?;
         self.db
@@ -261,7 +261,8 @@ impl Hashi {
             encryption_key,
             signing_key,
             store,
-            WEIGHT_REDUCTION_ALLOWED_DELTA,
+            threshold_basis_points,
+            weight_reduction_allowed_delta,
             chain_id,
             self.config.test_weight_divisor,
             batch_size_per_weight,

crates/hashi/src/mpc/mpc_except_signing.rs

@@ -74,6 +74,7 @@ const ERR_PUBLISH_CERT_FAILED: &str = "Failed to publish certificate";
 const EXPECT_THRESHOLD_VALIDATED: &str = "Threshold already validated";
 const EXPECT_THRESHOLD_MET: &str = "Already checked earlier that threshold is met";
 const EXPECT_SERIALIZATION_SUCCESS: &str = "Serialization should always succeed";
+const MAX_BASIS_POINTS: u32 = 10000;
 
 // DKG protocol
 // 1) A dealer sends out a message to all parties containing the encrypted shares and the public keys of the nonces.
@@ -123,7 +124,8 @@ impl MpcManager {
         encryption_key: PrivateKey<EncryptionGroupElement>,
         signing_key: Bls12381PrivateKey,
         public_message_store: Box<dyn PublicMessagesStore>,
-        allowed_delta: u16,
+        threshold_basis_points: u16,
+        weight_reduction_allowed_delta: u16,
         chain_id: &str,
         weight_divisor: Option<u16>,
         batch_size_per_weight: u16,
@@ -144,8 +146,12 @@ impl MpcManager {
             .get(&epoch)
             .ok_or_else(|| MpcError::InvalidConfig(format!("no committee for epoch {epoch}")))?
             .clone();
-        // TODO: Pass t and f as arguments instead of computing them
-        let (nodes, threshold) = build_reduced_nodes(&committee, allowed_delta, weight_divisor)?;
+        let (nodes, threshold) = build_reduced_nodes(
+            &committee,
+            threshold_basis_points,
+            weight_reduction_allowed_delta,
+            weight_divisor,
+        )?;
         let total_weight = nodes.total_weight();
         let max_faulty = ((total_weight - threshold) / 2).min(threshold - 1);
         let dkg_config = MpcConfig::new(epoch, nodes, threshold, max_faulty)?;
@@ -199,8 +205,12 @@ impl MpcManager {
         };
         let (previous_nodes, previous_threshold) = match previous_committee.as_ref() {
             Some(prev_committee) => {
-                let (nodes, threshold) =
-                    build_reduced_nodes(prev_committee, allowed_delta, weight_divisor)?;
+                let (nodes, threshold) = build_reduced_nodes(
+                    prev_committee,
+                    threshold_basis_points,
+                    weight_reduction_allowed_delta,
+                    weight_divisor,
+                )?;
                 (Some(nodes), Some(threshold))
             }
             None => (None, None),
@@ -3505,18 +3515,10 @@ fn compute_messages_hash(messages: &Messages) -> MessageHash {
     MessageHash::from(Blake2b256::digest(&bytes).digest)
 }
 
-fn compute_bft_threshold(total_weight: u16) -> MpcResult<u16> {
-    if total_weight == 0 {
-        return Err(MpcError::InvalidConfig(
-            "committee has zero total weight".into(),
-        ));
-    }
-    Ok((total_weight - 1) / 3 + 1)
-}
-
 fn build_reduced_nodes(
     committee: &Committee,
-    allowed_delta: u16,
+    threshold_basis_points: u16,
+    weight_reduction_allowed_delta: u16,
     test_weight_divisor: u16,
 ) -> MpcResult<(Nodes<EncryptionGroupElement>, u16)> {
     let nodes_vec: Vec<Node<EncryptionGroupElement>> = committee
@@ -3530,8 +3532,9 @@ fn build_reduced_nodes(
         })
         .collect();
     let total_weight: u16 = nodes_vec.iter().map(|n| n.weight).sum();
-    let threshold = compute_bft_threshold(total_weight)?;
-    Nodes::new_reduced(nodes_vec, threshold, allowed_delta, 1)
+    let threshold =
+        (total_weight as u32 * threshold_basis_points as u32).div_ceil(MAX_BASIS_POINTS) as u16;
+    Nodes::new_reduced(nodes_vec, threshold, weight_reduction_allowed_delta, 1)
         .map_err(|e| MpcError::CryptoError(e.to_string()))
 }
 

crates/hashi/src/mpc/mpc_except_signing_tests.rs

@@ -24,8 +24,9 @@ use std::sync::Arc;
 use std::sync::atomic::AtomicUsize;
 use std::sync::atomic::Ordering;
 
-/// Use 0 for allowed_delta in tests to disable weight reduction.
-const TEST_ALLOWED_DELTA: u16 = 0;
+const TEST_THRESHOLD_BASIS_POINTS: u16 = 3333;
+/// Use 0 for weight_reduction_allowed_delta in tests to disable weight reduction.
+const TEST_WEIGHT_REDUCTION_ALLOWED_DELTA: u16 = 0;
 /// Use 1 for test_weight_divisor in unit tests (they already use small weights).
 const TEST_WEIGHT_DIVISOR: u16 = 1;
 const TEST_CHAIN_ID: &str = "testchain";
@@ -284,7 +285,8 @@ impl TestSetup {
             self.encryption_keys[validator_index].clone(),
             self.signing_keys[validator_index].clone(),
             store,
-            TEST_ALLOWED_DELTA,
+            TEST_THRESHOLD_BASIS_POINTS,
+            TEST_WEIGHT_REDUCTION_ALLOWED_DELTA,
             TEST_CHAIN_ID,
             None,
             TEST_BATCH_SIZE_PER_WEIGHT,
@@ -897,7 +899,8 @@ fn test_mpc_manager_new_from_committee_set() {
         encryption_key,
         signing_key,
         Box::new(MockPublicMessagesStore),
-        TEST_ALLOWED_DELTA,
+        TEST_THRESHOLD_BASIS_POINTS,
+        TEST_WEIGHT_REDUCTION_ALLOWED_DELTA,
         TEST_CHAIN_ID,
         None,
         TEST_BATCH_SIZE_PER_WEIGHT,
@@ -960,7 +963,8 @@ fn test_mpc_manager_new_fails_if_no_committee_for_epoch() {
         encryption_keys[0].clone(),
         signing_keys[0].clone(),
         Box::new(MockPublicMessagesStore),
-        TEST_ALLOWED_DELTA,
+        TEST_THRESHOLD_BASIS_POINTS,
+        TEST_WEIGHT_REDUCTION_ALLOWED_DELTA,
         "test",
         None,
         TEST_BATCH_SIZE_PER_WEIGHT,
@@ -983,7 +987,8 @@ fn test_mpc_manager_new_with_weighted_committee() {
 
     let manager = setup.create_manager(0);
 
-    // With total_weight=15: max_faulty = (15-1)/3 = 4, threshold = 5
+    // With total_weight=15, threshold=ceil(15*3333/10000)=ceil(4.9995)=5
+    // max_faulty = min((15-5)/2, 5-1) = min(5, 4) = 4
     assert_eq!(manager.mpc_config.threshold, 5);
     assert_eq!(manager.mpc_config.max_faulty, 4);
 }
@@ -1262,7 +1267,7 @@ fn test_complete_dkg_success() {
     let mut rng = rand::thread_rng();
 
     // Use different weights: [3, 2, 4, 1, 2] (total = 12)
-    // threshold = (12 - 1) / 3 + 1 = 4
+    // threshold = ceil(12 * 3333 / 10000) = 4
     let weights = [3, 2, 4, 1, 2];
     let setup = TestSetup::with_weights(&weights);
 
@@ -4756,8 +4761,8 @@ struct RotationTestSetup {
 
 impl RotationTestSetup {
     /// Creates a rotation test setup with weighted validators and completed DKG.
-    /// Uses weights [3, 2, 4, 1, 2] (total = 12, threshold = 4).
-    /// Dealers are validators 0, 1, 4 (total weight = 7 >= threshold).
+    /// Uses weights [3, 2, 4, 1, 2] (total = 12, threshold = ceil(12*3333/10000) = 4).
+    /// Dealers are validators 0, 1, 4 (total weight = 7 >= threshold + max_faulty = 7).
     fn new() -> Self {
         let mut rng = rand::thread_rng();
         let weights = [3, 2, 4, 1, 2];
@@ -4816,8 +4821,13 @@ impl RotationTestSetup {
     /// This matches `run_as_party` behavior during live DKG.
     fn threshold_dealer_addresses(&self) -> Vec<Address> {
         let committee = self.setup.committee();
-        let (nodes, threshold) =
-            build_reduced_nodes(committee, TEST_ALLOWED_DELTA, TEST_WEIGHT_DIVISOR).unwrap();
+        let (nodes, threshold) = build_reduced_nodes(
+            committee,
+            TEST_THRESHOLD_BASIS_POINTS,
+            TEST_WEIGHT_REDUCTION_ALLOWED_DELTA,
+            TEST_WEIGHT_DIVISOR,
+        )
+        .unwrap();
         let mut result = Vec::new();
         let mut weight_sum = 0u16;
         for addr in self.certificates.keys() {
@@ -4837,8 +4847,13 @@ impl RotationTestSetup {
     fn prepare_for_rotation(&self, manager: &mut MpcManager) {
         let previous_committee = self.setup.committee_set.previous_committee().cloned();
         if let Some(ref prev) = previous_committee {
-            let (nodes, threshold) =
-                build_reduced_nodes(prev, TEST_ALLOWED_DELTA, TEST_WEIGHT_DIVISOR).unwrap();
+            let (nodes, threshold) = build_reduced_nodes(
+                prev,
+                TEST_THRESHOLD_BASIS_POINTS,
+                TEST_WEIGHT_REDUCTION_ALLOWED_DELTA,
+                TEST_WEIGHT_DIVISOR,
+            )
+            .unwrap();
             manager.previous_nodes = Some(nodes);
             manager.previous_threshold = Some(threshold);
         }
@@ -5830,7 +5845,8 @@ async fn test_prepare_previous_output_for_new_member() {
         new_member_encryption_key,
         new_member_signing_key,
         Box::new(InMemoryPublicMessagesStore::new()),
-        TEST_ALLOWED_DELTA,
+        TEST_THRESHOLD_BASIS_POINTS,
+        TEST_WEIGHT_REDUCTION_ALLOWED_DELTA,
         TEST_CHAIN_ID,
         None,
         TEST_BATCH_SIZE_PER_WEIGHT,
@@ -6965,7 +6981,8 @@ fn test_reconstruct_from_dkg_certificates_with_shifted_party_ids() {
         rotation_setup.setup.encryption_keys[shifted_member_index].clone(),
         rotation_setup.setup.signing_keys[shifted_member_index].clone(),
         Box::new(store),
-        TEST_ALLOWED_DELTA,
+        TEST_THRESHOLD_BASIS_POINTS,
+        TEST_WEIGHT_REDUCTION_ALLOWED_DELTA,
         TEST_CHAIN_ID,
         None,
         TEST_BATCH_SIZE_PER_WEIGHT,
@@ -7127,7 +7144,8 @@ fn test_reconstruct_from_dkg_certificates_stops_at_threshold() {
         setup.encryption_keys[target_index].clone(),
         setup.signing_keys[target_index].clone(),
         Box::new(store),
-        TEST_ALLOWED_DELTA,
+        TEST_THRESHOLD_BASIS_POINTS,
+        TEST_WEIGHT_REDUCTION_ALLOWED_DELTA,
         TEST_CHAIN_ID,
         None,
         TEST_BATCH_SIZE_PER_WEIGHT,
@@ -7207,7 +7225,8 @@ fn test_reconstruct_from_rotation_certificates_with_shifted_party_ids() {
             rotation_setup.setup.encryption_keys[dealer_idx].clone(),
             rotation_setup.setup.signing_keys[dealer_idx].clone(),
             Box::new(InMemoryPublicMessagesStore::new()),
-            TEST_ALLOWED_DELTA,
+            TEST_THRESHOLD_BASIS_POINTS,
+            TEST_WEIGHT_REDUCTION_ALLOWED_DELTA,
             TEST_CHAIN_ID,
             None,
             TEST_BATCH_SIZE_PER_WEIGHT,
@@ -7238,7 +7257,8 @@ fn test_reconstruct_from_rotation_certificates_with_shifted_party_ids() {
             rotation_setup.setup.encryption_keys[other_idx].clone(),
             rotation_setup.setup.signing_keys[other_idx].clone(),
             Box::new(InMemoryPublicMessagesStore::new()),
-            TEST_ALLOWED_DELTA,
+            TEST_THRESHOLD_BASIS_POINTS,
+            TEST_WEIGHT_REDUCTION_ALLOWED_DELTA,
             TEST_CHAIN_ID,
             None,
             TEST_BATCH_SIZE_PER_WEIGHT,
@@ -7325,7 +7345,8 @@ fn test_reconstruct_from_rotation_certificates_with_shifted_party_ids() {
         rotation_setup.setup.encryption_keys[shifted_member_index].clone(),
         rotation_setup.setup.signing_keys[shifted_member_index].clone(),
         Box::new(store),
-        TEST_ALLOWED_DELTA,
+        TEST_THRESHOLD_BASIS_POINTS,
+        TEST_WEIGHT_REDUCTION_ALLOWED_DELTA,
         TEST_CHAIN_ID,
         None,
         TEST_BATCH_SIZE_PER_WEIGHT,

crates/hashi/src/onchain/mod.rs

@@ -394,6 +394,17 @@ impl OnchainState {
         self.state().hashi().config.bitcoin_confirmation_threshold()
     }
 
+    pub fn mpc_threshold_basis_points(&self) -> u16 {
+        self.state().hashi().config.mpc_threshold_basis_points()
+    }
+
+    pub fn mpc_weight_reduction_allowed_delta(&self) -> u16 {
+        self.state()
+            .hashi()
+            .config
+            .mpc_weight_reduction_allowed_delta()
+    }
+
     pub fn bridge_service_client(
         &self,
         validator: &Address,

crates/hashi/src/onchain/types.rs

@@ -454,6 +454,10 @@ pub struct Config {
 // This constant mirrors the value in btc_config.move and must be kept in sync.
 const DUST_RELAY_MIN_VALUE: u64 = 546;
 
+// These mirror the defaults in mpc_config.move and must be kept in sync.
+pub const DEFAULT_MPC_THRESHOLD_BASIS_POINTS: u16 = 3333;
+pub const DEFAULT_MPC_WEIGHT_REDUCTION_ALLOWED_DELTA: u16 = 800;
+
 impl Config {
     /// Minimum deposit amount, mirroring the floor logic in btc_config.move.
     pub fn bitcoin_deposit_minimum(&self) -> u64 {
@@ -495,6 +499,24 @@ impl Config {
             _ => 6,
         }
     }
+
+    pub fn mpc_threshold_basis_points(&self) -> u16 {
+        match self.config.get("mpc_threshold_basis_points") {
+            Some(ConfigValue::U64(v)) => {
+                u16::try_from(*v).expect("mpc_threshold_basis_points exceeds u16::MAX")
+            }
+            _ => DEFAULT_MPC_THRESHOLD_BASIS_POINTS,
+        }
+    }
+
+    pub fn mpc_weight_reduction_allowed_delta(&self) -> u16 {
+        match self.config.get("mpc_weight_reduction_allowed_delta") {
+            Some(ConfigValue::U64(v)) => {
+                u16::try_from(*v).expect("mpc_weight_reduction_allowed_delta exceeds u16::MAX")
+            }
+            _ => DEFAULT_MPC_WEIGHT_REDUCTION_ALLOWED_DELTA,
+        }
+    }
 }
 
 #[derive(Debug)]

crates/internal-tools/src/key_recovery.rs

@@ -113,14 +113,18 @@ pub async fn run(args: Args, onchain_state: &OnchainState, chain_id: &str) -> an
         let session_id = SessionId::new(chain_id, reconstruction_epoch, &ProtocolType::KeyRotation);
         let mut manager = {
             let state = onchain_state.state();
+            let hashi = state.hashi();
+            let threshold_basis_points = hashi.config.mpc_threshold_basis_points();
+            let weight_reduction_allowed_delta = hashi.config.mpc_weight_reduction_allowed_delta();
             MpcManager::new(
                 validator_address,
-                &state.hashi().committees,
+                &hashi.committees,
                 session_id,
                 encryption_key,
                 dummy_signing_key.clone(),
                 Box::new(store),
-                800, // allowed_delta (same as devnet)
+                threshold_basis_points,
+                weight_reduction_allowed_delta,
                 chain_id,
                 None, // weight_divisor
                 0,    // batch_size_per_weight (unused for reconstruction)