Use a MuSig signature to publish validator set key pairs to Serai

The processor/coordinator flow still has to be rewritten.

Cargo.lock

@@ -8754,7 +8754,9 @@ version = "0.1.0"
 dependencies = [
  "bitcoin",
  "ciphersuite",
+ "frost-schnorrkel",
  "lazy_static",
+ "modular-frost",
  "monero-serai",
  "parity-scale-codec",
  "rand_core 0.6.4",
@@ -8764,6 +8766,7 @@ dependencies = [
  "subxt",
  "thiserror",
  "tokio",
+ "zeroize",
 ]
 
 [[package]]
@@ -10995,11 +10998,15 @@ dependencies = [
 name = "validator-sets-pallet"
 version = "0.1.0"
 dependencies = [
+ "ciphersuite",
+ "dkg",
  "frame-support",
  "frame-system",
+ "hashbrown 0.13.2",
  "parity-scale-codec",
  "scale-info",
  "serai-primitives",
+ "sp-application-crypto",
  "sp-core",
  "validator-sets-primitives",
 ]

substrate/client/Cargo.toml

@@ -13,6 +13,7 @@ all-features = true
 rustdoc-args = ["--cfg", "docsrs"]
 
 [dependencies]
+zeroize = "^1.5"
 thiserror = { version = "1", optional = true }
 
 scale = { package = "parity-scale-codec", version = "3" }
@@ -28,6 +29,17 @@ bitcoin = { version = "0.30", optional = true }
 ciphersuite = { path = "../../crypto/ciphersuite", version = "0.3", optional = true }
 monero-serai = { path = "../../coins/monero", version = "0.1.4-alpha", optional = true }
 
+[dev-dependencies]
+lazy_static = "1"
+
+rand_core = "0.6"
+
+ciphersuite = { path = "../../crypto/ciphersuite", features = ["ristretto"] }
+frost = { package = "modular-frost", path = "../../crypto/frost", features = ["tests"] }
+schnorrkel = { path = "../../crypto/schnorrkel", package = "frost-schnorrkel" }
+
+tokio = "1"
+
 [features]
 serai = ["thiserror", "scale-info", "subxt"]
 
@@ -38,10 +50,3 @@ monero = ["coins", "ciphersuite/ed25519", "monero-serai"]
 # Assumes the default usage is to use Serai as a DEX, which doesn't actually
 # require connecting to a Serai node
 default = ["bitcoin", "monero"]
-
-[dev-dependencies]
-lazy_static = "1"
-
-rand_core = "0.6"
-
-tokio = "1"

substrate/client/src/serai/in_instructions.rs

@@ -33,7 +33,7 @@ impl Serai {
       .await
   }
 
-  pub fn execute_batch(&self, batch: SignedBatch) -> Encoded {
-    self.unsigned::<InInstructions, _>(&in_instructions::Call::<Runtime>::execute_batch { batch })
+  pub fn execute_batch(batch: SignedBatch) -> Encoded {
+    Self::unsigned::<InInstructions, _>(&in_instructions::Call::<Runtime>::execute_batch { batch })
   }
 }

substrate/client/src/serai/mod.rs

@@ -269,7 +269,7 @@ impl Serai {
       .map_err(SeraiError::RpcError)
   }
 
-  fn unsigned<P: 'static, C: Encode>(&self, call: &C) -> Encoded {
+  fn unsigned<P: 'static, C: Encode>(call: &C) -> Encoded {
     // TODO: Should Serai purge the old transaction code AND set this to 0/1?
     const TRANSACTION_VERSION: u8 = 4;
 

substrate/client/src/serai/validator_sets.rs

@@ -1,10 +1,12 @@
+use sp_core::sr25519::Signature;
+
 use serai_runtime::{validator_sets, ValidatorSets, Runtime};
 pub use validator_sets::primitives;
 use primitives::{ValidatorSet, ValidatorSetData, KeyPair};
 
-use subxt::tx::Payload;
+use subxt::utils::Encoded;
 
-use crate::{primitives::NetworkId, Serai, SeraiError, Composite, scale_value, scale_composite};
+use crate::{primitives::NetworkId, Serai, SeraiError, scale_value};
 
 const PALLET: &str = "ValidatorSets";
 
@@ -20,15 +22,6 @@ impl Serai {
       .await
   }
 
-  pub async fn get_vote_events(
-    &self,
-    block: [u8; 32],
-  ) -> Result<Vec<ValidatorSetsEvent>, SeraiError> {
-    self
-      .events::<ValidatorSets, _>(block, |event| matches!(event, ValidatorSetsEvent::Vote { .. }))
-      .await
-  }
-
   pub async fn get_key_gen_events(
     &self,
     block: [u8; 32],
@@ -52,17 +45,35 @@ impl Serai {
       .await
   }
 
+  pub async fn get_validator_set_musig_key(
+    &self,
+    set: ValidatorSet,
+  ) -> Result<Option<[u8; 32]>, SeraiError> {
+    self
+      .storage(
+        PALLET,
+        "MuSigKeys",
+        Some(vec![scale_value(set)]),
+        self.get_latest_block_hash().await?,
+      )
+      .await
+  }
+
   pub async fn get_keys(&self, set: ValidatorSet) -> Result<Option<KeyPair>, SeraiError> {
     self
       .storage(PALLET, "Keys", Some(vec![scale_value(set)]), self.get_latest_block_hash().await?)
       .await
   }
 
-  pub fn vote(network: NetworkId, key_pair: KeyPair) -> Payload<Composite<()>> {
-    Payload::new(
-      PALLET,
-      "vote",
-      scale_composite(validator_sets::Call::<Runtime>::vote { network, key_pair }),
-    )
+  pub fn set_validator_set_keys(
+    network: NetworkId,
+    key_pair: KeyPair,
+    signature: Signature,
+  ) -> Encoded {
+    Self::unsigned::<ValidatorSets, _>(&validator_sets::Call::<Runtime>::set_keys {
+      network,
+      key_pair,
+      signature,
+    })
   }
 }

substrate/client/tests/common/in_instructions.rs

@@ -9,9 +9,10 @@ use serai_client::{
     primitives::{Batch, SignedBatch},
     InInstructionsEvent,
   },
+  Serai,
 };
 
-use crate::common::{serai, tx::publish_tx, validator_sets::vote_in_keys};
+use crate::common::{serai, tx::publish_tx, validator_sets::set_validator_set_keys};
 
 #[allow(dead_code)]
 pub async fn provide_batch(batch: Batch) -> [u8; 32] {
@@ -24,15 +25,15 @@ pub async fn provide_batch(batch: Batch) -> [u8; 32] {
     keys
   } else {
     let keys = (pair.public(), vec![].try_into().unwrap());
-    vote_in_keys(set, keys.clone()).await;
+    set_validator_set_keys(set, keys.clone()).await;
     keys
   };
   assert_eq!(keys.0, pair.public());
 
-  let block = publish_tx(
-    &serai
-      .execute_batch(SignedBatch { batch: batch.clone(), signature: pair.sign(&batch.encode()) }),
-  )
+  let block = publish_tx(&Serai::execute_batch(SignedBatch {
+    batch: batch.clone(),
+    signature: pair.sign(&batch.encode()),
+  }))
   .await;
 
   let batches = serai.get_batch_events(block).await.unwrap();

substrate/client/tests/common/validator_sets.rs

@@ -1,42 +1,68 @@
-use sp_core::Pair;
+use std::collections::HashMap;
+
+use zeroize::Zeroizing;
+use rand_core::OsRng;
+
+use scale::Encode;
+
+use sp_core::{Pair, sr25519::Signature};
+
+use ciphersuite::{group::GroupEncoding, Ciphersuite, Ristretto};
+use frost::dkg::musig::*;
+use schnorrkel::Schnorrkel;
 
 use serai_client::{
-  subxt::config::extrinsic_params::BaseExtrinsicParamsBuilder,
-  primitives::{SeraiAddress, insecure_pair_from_name},
+  primitives::insecure_pair_from_name,
   validator_sets::{
     primitives::{ValidatorSet, KeyPair},
     ValidatorSetsEvent,
   },
-  PairSigner, Serai,
+  Serai,
 };
 
 use crate::common::{serai, tx::publish_tx};
 
 #[allow(dead_code)]
-pub async fn vote_in_keys(set: ValidatorSet, key_pair: KeyPair) -> [u8; 32] {
+pub async fn set_validator_set_keys(set: ValidatorSet, key_pair: KeyPair) -> [u8; 32] {
   let pair = insecure_pair_from_name("Alice");
   let public = pair.public();
 
   let serai = serai().await;
+  let public_key = <Ristretto as Ciphersuite>::read_G::<&[u8]>(&mut public.0.as_ref()).unwrap();
+  assert_eq!(
+    serai.get_validator_set_musig_key(set).await.unwrap().unwrap(),
+    musig_key::<Ristretto>(&[public_key]).unwrap().to_bytes()
+  );
+
+  let secret_key = <Ristretto as Ciphersuite>::read_F::<&[u8]>(
+    &mut pair.as_ref().secret.to_bytes()[.. 32].as_ref(),
+  )
+  .unwrap();
+  assert_eq!(Ristretto::generator() * secret_key, public_key);
+  let threshold_keys = musig::<Ristretto>(&Zeroizing::new(secret_key), &[public_key]).unwrap();
+  assert_eq!(
+    serai.get_validator_set_musig_key(set).await.unwrap().unwrap(),
+    threshold_keys.group_key().to_bytes()
+  );
+
+  let sig = frost::tests::sign_without_caching(
+    &mut OsRng,
+    frost::tests::algorithm_machines(
+      &mut OsRng,
+      Schnorrkel::new(b"substrate"),
+      &HashMap::from([(threshold_keys.params().i(), threshold_keys.into())]),
+    ),
+    &key_pair.encode(),
+  );
 
   // Vote in a key pair
-  let address = SeraiAddress::from(pair.public());
-  let block = publish_tx(
-    &serai
-      .sign(
-        &PairSigner::new(pair),
-        &Serai::vote(set.network, key_pair.clone()),
-        serai.get_nonce(&address).await.unwrap(),
-        BaseExtrinsicParamsBuilder::new(),
-      )
-      .unwrap(),
-  )
+  let block = publish_tx(&Serai::set_validator_set_keys(
+    set.network,
+    key_pair.clone(),
+    Signature(sig.to_bytes()),
+  ))
   .await;
 
-  assert_eq!(
-    serai.get_vote_events(block).await.unwrap(),
-    vec![ValidatorSetsEvent::Vote { voter: public, set, key_pair: key_pair.clone(), votes: 1 }]
-  );
   assert_eq!(
     serai.get_key_gen_events(block).await.unwrap(),
     vec![ValidatorSetsEvent::KeyGen { set, key_pair: key_pair.clone() }]

substrate/client/tests/validator_sets.rs

@@ -2,6 +2,9 @@ use rand_core::{RngCore, OsRng};
 
 use sp_core::{sr25519::Public, Pair};
 
+use ciphersuite::{group::GroupEncoding, Ciphersuite, Ristretto};
+use frost::dkg::musig::musig_key;
+
 use serai_client::{
   primitives::{NETWORKS, NetworkId, insecure_pair_from_name},
   validator_sets::{
@@ -12,10 +15,10 @@ use serai_client::{
 };
 
 mod common;
-use common::{serai, validator_sets::vote_in_keys};
+use common::{serai, validator_sets::set_validator_set_keys};
 
 serai_test!(
-  async fn vote_keys() {
+  async fn set_validator_set_keys_test() {
     let network = NetworkId::Bitcoin;
     let set = ValidatorSet { session: Session(0), network };
 
@@ -51,14 +54,20 @@ serai_test!(
     assert_eq!(set_data.network, NETWORKS[&NetworkId::Bitcoin]);
     let participants_ref: &[_] = set_data.participants.as_ref();
     assert_eq!(participants_ref, [(public, set_data.bond)].as_ref());
-
-    let block = vote_in_keys(set, key_pair.clone()).await;
-
-    // While the vote_in_keys function should handle this, it's beneficial to independently test it
     assert_eq!(
-      serai.get_vote_events(block).await.unwrap(),
-      vec![ValidatorSetsEvent::Vote { voter: public, set, key_pair: key_pair.clone(), votes: 1 }]
+      serai.get_validator_set_musig_key(set).await.unwrap().unwrap(),
+      musig_key::<Ristretto>(&[<Ristretto as Ciphersuite>::read_G::<&[u8]>(
+        &mut public.0.as_ref()
+      )
+      .unwrap()])
+      .unwrap()
+      .to_bytes()
     );
+
+    let block = set_validator_set_keys(set, key_pair.clone()).await;
+
+    // While the set_validator_set_keys function should handle this, it's beneficial to
+    // independently test it
     assert_eq!(
       serai.get_key_gen_events(block).await.unwrap(),
       vec![ValidatorSetsEvent::KeyGen { set, key_pair: key_pair.clone() }]

substrate/in-instructions/pallet/src/lib.rs

@@ -114,7 +114,7 @@ pub mod pallet {
       // Match to be exhaustive
       let batch = match call {
         Call::execute_batch { ref batch } => batch,
-        _ => Err(InvalidTransaction::Call)?,
+        Call::__Ignore(_, _) => unreachable!(),
       };
 
       let network = batch.batch.network;

substrate/runtime/src/lib.rs

@@ -174,7 +174,7 @@ impl Contains<RuntimeCall> for CallFilter {
     }
 
     if let RuntimeCall::ValidatorSets(call) = call {
-      return matches!(call, validator_sets::Call::vote { .. });
+      return matches!(call, validator_sets::Call::set_keys { .. });
     }
 
     false

substrate/validator-sets/pallet/Cargo.toml

@@ -12,19 +12,28 @@ all-features = true
 rustdoc-args = ["--cfg", "docsrs"]
 
 [dependencies]
+hashbrown = { version = "0.13", default-features = false }
+
+ciphersuite = { version = "0.3", path = "../../../crypto/ciphersuite", default-features = false, features = ["ristretto"] }
+dkg = { version = "0.4", path = "../../../crypto/dkg", default-features = false }
+
 scale = { package = "parity-scale-codec", version = "3", default-features = false, features = ["derive"] }
 scale-info = { version = "2", default-features = false, features = ["derive"] }
 
 sp-core = { git = "https://github.com/serai-dex/substrate", default-features = false }
+sp-application-crypto = { git = "https://github.com/serai-dex/substrate", default-features = false }
 
 frame-system = { git = "https://github.com/serai-dex/substrate", default-features = false }
 frame-support = { git = "https://github.com/serai-dex/substrate", default-features = false }
 
-serai-primitives = { path = "../..//primitives", default-features = false }
+serai-primitives = { path = "../../primitives", default-features = false }
 validator-sets-primitives = { path = "../primitives", default-features = false }
 
 [features]
 std = [
+  "ciphersuite/std",
+  "dkg/std",
+
   "scale/std",
   "scale-info/std",
 

substrate/validator-sets/pallet/src/lib.rs

@@ -5,6 +5,9 @@
 pub mod pallet {
   use scale_info::TypeInfo;
 
+  use sp_core::sr25519::{Public, Signature};
+  use sp_application_crypto::RuntimePublic;
+
   use frame_system::pallet_prelude::*;
   use frame_support::pallet_prelude::*;
 
@@ -13,7 +16,7 @@ pub mod pallet {
   use primitives::*;
 
   #[pallet::config]
-  pub trait Config: frame_system::Config<AccountId = sp_core::sr25519::Public> + TypeInfo {
+  pub trait Config: frame_system::Config<AccountId = Public> + TypeInfo {
     type RuntimeEvent: IsType<<Self as frame_system::Config>::RuntimeEvent> + From<Event<Self>>;
   }
 
@@ -46,59 +49,57 @@ pub mod pallet {
   pub type ValidatorSets<T: Config> =
     StorageMap<_, Twox64Concat, ValidatorSet, ValidatorSetData, OptionQuery>;
 
+  /// The MuSig key for a validator set.
+  #[pallet::storage]
+  #[pallet::getter(fn musig_key)]
+  pub type MuSigKeys<T: Config> = StorageMap<_, Twox64Concat, ValidatorSet, Public, OptionQuery>;
+
   /// The key pair for a given validator set instance.
   #[pallet::storage]
   #[pallet::getter(fn keys)]
   pub type Keys<T: Config> = StorageMap<_, Twox64Concat, ValidatorSet, KeyPair, OptionQuery>;
 
-  /// If an account has voted for a specific key pair or not.
-  // This prevents a validator from voting multiple times.
-  #[pallet::storage]
-  #[pallet::getter(fn voted)]
-  pub type Voted<T: Config> =
-    StorageMap<_, Blake2_128Concat, (T::AccountId, KeyPair), (), OptionQuery>;
-
-  /// How many times a key pair has been voted for. Once consensus is reached, the keys will be
-  /// adopted.
-  #[pallet::storage]
-  #[pallet::getter(fn vote_count)]
-  pub type VoteCount<T: Config> =
-    StorageMap<_, Blake2_128Concat, (ValidatorSet, KeyPair), u16, ValueQuery>;
-
   #[pallet::event]
   #[pallet::generate_deposit(pub(super) fn deposit_event)]
   pub enum Event<T: Config> {
-    NewSet {
-      set: ValidatorSet,
-    },
-    Vote {
-      voter: T::AccountId,
-      set: ValidatorSet,
-      key_pair: KeyPair,
-      // Amount of votes the key now has
-      votes: u16,
-    },
-    KeyGen {
-      set: ValidatorSet,
-      key_pair: KeyPair,
-    },
+    NewSet { set: ValidatorSet },
+    KeyGen { set: ValidatorSet, key_pair: KeyPair },
   }
 
   #[pallet::genesis_build]
   impl<T: Config> GenesisBuild<T> for GenesisConfig<T> {
     fn build(&self) {
+      use ciphersuite::{group::GroupEncoding, Ciphersuite, Ristretto};
+
+      let hash_set = self.participants.iter().map(|key| key.0).collect::<hashbrown::HashSet<[u8; 32]>>();
+      if hash_set.len() != self.participants.len()
+      {
+        panic!("participants contained duplicates");
+      }
+
       let mut participants = Vec::new();
+      let mut keys = Vec::new();
       for participant in self.participants.clone() {
+        keys.push(
+          <Ristretto as Ciphersuite>::read_G::<&[u8]>(
+            &mut participant.0.as_ref(),
+          )
+          .expect("invalid participant"),
+        );
         participants.push((participant, self.bond));
       }
       let participants = BoundedVec::try_from(participants).unwrap();
 
       for (id, network) in self.networks.clone() {
         let set = ValidatorSet { session: Session(0), network: id };
+        // TODO: Should this be split up? Substrate will read this entire struct into mem on every
+        // read, not just accessed variables
         ValidatorSets::<T>::set(
           set,
           Some(ValidatorSetData { bond: self.bond, network, participants: participants.clone() }),
         );
+
+        MuSigKeys::<T>::set(set, Some(Public(dkg::musig::musig_key::<Ristretto>(&keys).unwrap().to_bytes())));
         Pallet::<T>::deposit_event(Event::NewSet { set })
       }
     }
@@ -108,63 +109,90 @@ pub mod pallet {
   pub enum Error<T> {
     /// Validator Set doesn't exist.
     NonExistentValidatorSet,
-    /// Non-validator is voting.
-    NotValidator,
     /// Validator Set already generated keys.
     AlreadyGeneratedKeys,
-    /// Vvalidator has already voted for these keys.
-    AlreadyVoted,
+    /// An invalid MuSig signature was provided.
+    BadSignature,
+  }
+
+  impl<T: Config> Pallet<T> {
+    fn verify_signature(
+      set: ValidatorSet,
+      key_pair: &KeyPair,
+      signature: &Signature,
+    ) -> Result<(), Error<T>> {
+      if Keys::<T>::get(set).is_some() {
+        Err(Error::AlreadyGeneratedKeys)?
+      }
+
+      let Some(musig_key) = MuSigKeys::<T>::get(set) else {
+        Err(Error::NonExistentValidatorSet)?
+      };
+      if !musig_key.verify(&key_pair.encode(), signature) {
+        Err(Error::BadSignature)?;
+      }
+
+      Ok(())
+    }
   }
 
   #[pallet::call]
   impl<T: Config> Pallet<T> {
     #[pallet::call_index(0)]
     #[pallet::weight(0)] // TODO
-    pub fn vote(origin: OriginFor<T>, network: NetworkId, key_pair: KeyPair) -> DispatchResult {
-      let signer = ensure_signed(origin)?;
-      // TODO: Do we need to check the key is within the length bounds?
-      // The docs suggest the BoundedVec will create/write, yet not read, which could be an issue
-      // if it can be passed in
+    pub fn set_keys(
+      origin: OriginFor<T>,
+      network: NetworkId,
+      key_pair: KeyPair,
+      signature: Signature,
+    ) -> DispatchResult {
+      ensure_none(origin)?;
 
       // TODO: Get session
       let session: Session = Session(0);
 
       // Confirm a key hasn't been set for this set instance
       let set = ValidatorSet { session, network };
-      if Keys::<T>::get(set).is_some() {
-        Err(Error::<T>::AlreadyGeneratedKeys)?;
-      }
+      Self::verify_signature(set, &key_pair, &signature)?;
 
-      // Confirm the signer is a validator in the set
-      let data = ValidatorSets::<T>::get(set).ok_or(Error::<T>::NonExistentValidatorSet)?;
-      if !data.participants.iter().any(|participant| participant.0 == signer) {
-        Err(Error::<T>::NotValidator)?;
-      }
-
-      // Confirm this signer hasn't already voted for these keys
-      if Voted::<T>::get((&signer, &key_pair)).is_some() {
-        Err(Error::<T>::AlreadyVoted)?;
-      }
-      Voted::<T>::set((&signer, &key_pair), Some(()));
-
-      // Add their vote
-      let votes = VoteCount::<T>::mutate((set, &key_pair), |value| {
-        *value += 1;
-        *value
-      });
-
-      Self::deposit_event(Event::Vote { voter: signer, set, key_pair: key_pair.clone(), votes });
-
-      // If we've reached consensus, set the key
-      if usize::try_from(votes).unwrap() == data.participants.len() {
-        Keys::<T>::set(set, Some(key_pair.clone()));
-        Self::deposit_event(Event::KeyGen { set, key_pair });
-      }
+      Keys::<T>::set(set, Some(key_pair.clone()));
+      Self::deposit_event(Event::KeyGen { set, key_pair });
 
       Ok(())
     }
   }
 
+  #[pallet::validate_unsigned]
+  impl<T: Config> ValidateUnsigned for Pallet<T> {
+    type Call = Call<T>;
+
+    fn validate_unsigned(_: TransactionSource, call: &Self::Call) -> TransactionValidity {
+      // Match to be exhaustive
+      let (network, key_pair, signature) = match call {
+        Call::set_keys { network, ref key_pair, ref signature } => (network, key_pair, signature),
+        Call::__Ignore(_, _) => unreachable!(),
+      };
+
+      // TODO: Get the latest session
+      let session = Session(0);
+
+      let set = ValidatorSet { session, network: *network };
+      match Self::verify_signature(set, key_pair, signature) {
+        Err(Error::AlreadyGeneratedKeys) => Err(InvalidTransaction::Stale)?,
+        Err(Error::NonExistentValidatorSet) | Err(Error::BadSignature) => Err(InvalidTransaction::BadProof)?,
+        Err(Error::__Ignore(_, _)) => unreachable!(),
+        Ok(()) => (),
+      }
+
+      ValidTransaction::with_tag_prefix("validator-sets")
+        .and_provides(set)
+        // Set a 10 block longevity, though this should be included in the next block
+        .longevity(10)
+        .propagate(true)
+        .build()
+    }
+  }
+
   // TODO: Support session rotation
 }