Remove borsh from dkg

It pulls in a lot of bespoke dependencies for little utility directly present.

Moves the necessary code into the processor.

Cargo.lock

@@ -2444,7 +2444,6 @@ dependencies = [
 name = "dkg"
 version = "0.6.1"
 dependencies = [
- "borsh",
  "ciphersuite 0.4.2",
  "std-shims 0.1.5",
  "thiserror 2.0.17",

coordinator/src/db.rs

@@ -103,7 +103,7 @@ mod _internal_db {
       // Tributary transactions to publish from the DKG confirmation task
       TributaryTransactionsFromDkgConfirmation: (set: ExternalValidatorSet) -> Transaction,
       // Participants to remove
-      RemoveParticipant: (set: ExternalValidatorSet) -> Participant,
+      RemoveParticipant: (set: ExternalValidatorSet) -> u16,
     }
   }
 }
@@ -139,10 +139,11 @@ impl RemoveParticipant {
   pub(crate) fn send(txn: &mut impl DbTxn, set: ExternalValidatorSet, participant: Participant) {
     // If this set has yet to be retired, send this transaction
     if RetiredTributary::get(txn, set.network).map(|session| session.0) < Some(set.session.0) {
-      _internal_db::RemoveParticipant::send(txn, set, &participant);
+      _internal_db::RemoveParticipant::send(txn, set, &u16::from(participant));
     }
   }
   pub(crate) fn try_recv(txn: &mut impl DbTxn, set: ExternalValidatorSet) -> Option<Participant> {
     _internal_db::RemoveParticipant::try_recv(txn, set)
+      .map(|i| Participant::new(i).expect("sent invalid participant index for removal"))
   }
 }

crypto/dkg/Cargo.toml

@@ -23,19 +23,12 @@ thiserror = { version = "2", default-features = false }
 
 std-shims = { version = "0.1", path = "../../common/std-shims", default-features = false, features = ["alloc"] }
 
-borsh = { version = "1", default-features = false, features = ["derive", "de_strict_order"], optional = true }
-
 ciphersuite = { path = "../ciphersuite", version = "^0.4.1", default-features = false, features = ["alloc"] }
 
 [features]
 std = [
   "thiserror/std",
-
   "std-shims/std",
-
-  "borsh?/std",
-
   "ciphersuite/std",
 ]
-borsh = ["dep:borsh"]
 default = ["std"]

crypto/dkg/src/lib.rs

@@ -22,7 +22,6 @@ use ciphersuite::{
 
 /// The ID of a participant, defined as a non-zero u16.
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Zeroize)]
-#[cfg_attr(feature = "borsh", derive(borsh::BorshSerialize))]
 pub struct Participant(u16);
 impl Participant {
   /// Create a new Participant identifier from a u16.
@@ -129,18 +128,8 @@ pub enum DkgError {
   NotParticipating,
 }
 
-// Manually implements BorshDeserialize so we can enforce it's a valid index
-#[cfg(feature = "borsh")]
-impl borsh::BorshDeserialize for Participant {
-  fn deserialize_reader<R: io::Read>(reader: &mut R) -> io::Result<Self> {
-    Participant::new(u16::deserialize_reader(reader)?)
-      .ok_or_else(|| io::Error::other("invalid participant"))
-  }
-}
-
 /// Parameters for a multisig.
 #[derive(Clone, Copy, PartialEq, Eq, Debug, Zeroize)]
-#[cfg_attr(feature = "borsh", derive(borsh::BorshSerialize))]
 pub struct ThresholdParams {
   /// Participants needed to sign on behalf of the group.
   t: u16,
@@ -210,16 +199,6 @@ impl ThresholdParams {
   }
 }
 
-#[cfg(feature = "borsh")]
-impl borsh::BorshDeserialize for ThresholdParams {
-  fn deserialize_reader<R: io::Read>(reader: &mut R) -> io::Result<Self> {
-    let t = u16::deserialize_reader(reader)?;
-    let n = u16::deserialize_reader(reader)?;
-    let i = Participant::deserialize_reader(reader)?;
-    ThresholdParams::new(t, n, i).map_err(|e| io::Error::other(format!("{e:?}")))
-  }
-}
-
 /// A method of interpolation.
 #[derive(Clone, PartialEq, Eq, Debug, Zeroize)]
 pub enum Interpolation<F: Zeroize + PrimeField> {

processor/key-gen/src/db.rs

@@ -31,7 +31,15 @@ struct RawParams {
 
 #[derive(BorshSerialize, BorshDeserialize)]
 pub(crate) struct Participations {
+  #[borsh(
+    serialize_with = "messages::borsh_serialize_participant_map",
+    deserialize_with = "messages::borsh_deserialize_participant_map"
+  )]
   pub(crate) substrate_participations: HashMap<Participant, Vec<u8>>,
+  #[borsh(
+    serialize_with = "messages::borsh_serialize_participant_map",
+    deserialize_with = "messages::borsh_deserialize_participant_map"
+  )]
   pub(crate) network_participations: HashMap<Participant, Vec<u8>>,
 }
 

processor/messages/Cargo.toml

@@ -23,7 +23,7 @@ hex = { version = "0.4", default-features = false, features = ["std"] }
 scale = { package = "parity-scale-codec", version = "3", default-features = false, features = ["std"] }
 borsh = { version = "1", default-features = false, features = ["std", "derive", "de_strict_order"] }
 
-dkg = { path = "../../crypto/dkg", default-features = false, features = ["std", "borsh"] }
+dkg = { path = "../../crypto/dkg", default-features = false, features = ["std"] }
 
 serai-primitives = { path = "../../substrate/primitives", default-features = false, features = ["std", "borsh"] }
 in-instructions-primitives = { package = "serai-in-instructions-primitives", path = "../../substrate/in-instructions/primitives", default-features = false, features = ["std", "borsh"] }

processor/messages/src/lib.rs

@@ -21,6 +21,44 @@ pub struct SubstrateContext {
   pub network_latest_finalized_block: BlockHash,
 }
 
+pub fn borsh_serialize_participant<W: borsh::io::Write>(
+  value: &Participant,
+  writer: &mut W,
+) -> borsh::io::Result<()> {
+  u16::from(*value).serialize(writer)
+}
+pub fn borsh_deserialize_participant<R: borsh::io::Read>(
+  reader: &mut R,
+) -> borsh::io::Result<Participant> {
+  u16::deserialize_reader(reader).and_then(|p| {
+    Participant::new(p)
+      .ok_or_else(|| borsh::io::Error::other("invalid `Participant` despite valid `u16`"))
+  })
+}
+
+pub fn borsh_serialize_participant_map<W: borsh::io::Write>(
+  value: &HashMap<Participant, Vec<u8>>,
+  writer: &mut W,
+) -> borsh::io::Result<()> {
+  value
+    .iter()
+    .map(|(key, value)| (u16::from(*key), value))
+    .collect::<HashMap<u16, &Vec<u8>>>()
+    .serialize(writer)
+}
+pub fn borsh_deserialize_participant_map<R: borsh::io::Read>(
+  reader: &mut R,
+) -> borsh::io::Result<HashMap<Participant, Vec<u8>>> {
+  HashMap::<u16, Vec<u8>>::deserialize_reader(reader)?
+    .into_iter()
+    .map(|(key, value)| {
+      Participant::new(key)
+        .ok_or_else(|| borsh::io::Error::other("invalid `Participant` despite valid `u16` in map"))
+        .map(|key| (key, value))
+    })
+    .collect()
+}
+
 pub mod key_gen {
   use super::*;
 
@@ -33,7 +71,15 @@ pub mod key_gen {
     /// Received participations for the specified key generation protocol.
     ///
     /// This is sent by the Coordinator's Tributary scanner.
-    Participation { session: Session, participant: Participant, participation: Vec<u8> },
+    Participation {
+      session: Session,
+      #[borsh(
+        serialize_with = "borsh_serialize_participant",
+        deserialize_with = "borsh_deserialize_participant"
+      )]
+      participant: Participant,
+      participation: Vec<u8>,
+    },
   }
 
   impl core::fmt::Debug for CoordinatorMessage {
@@ -58,11 +104,25 @@ pub mod key_gen {
   #[derive(Clone, BorshSerialize, BorshDeserialize)]
   pub enum ProcessorMessage {
     // Participated in the specified key generation protocol.
-    Participation { session: Session, participation: Vec<u8> },
+    Participation {
+      session: Session,
+      participation: Vec<u8>,
+    },
     // Resulting keys from the specified key generation protocol.
-    GeneratedKeyPair { session: Session, substrate_key: [u8; 32], network_key: Vec<u8> },
+    GeneratedKeyPair {
+      session: Session,
+      substrate_key: [u8; 32],
+      network_key: Vec<u8>,
+    },
     // Blame this participant.
-    Blame { session: Session, participant: Participant },
+    Blame {
+      session: Session,
+      #[borsh(
+        serialize_with = "borsh_serialize_participant",
+        deserialize_with = "borsh_deserialize_participant"
+      )]
+      participant: Participant,
+    },
   }
 
   impl core::fmt::Debug for ProcessorMessage {
@@ -127,11 +187,25 @@ pub mod sign {
     /// Received preprocesses for the specified signing protocol.
     ///
     /// This is sent by the Coordinator's Tributary scanner.
-    Preprocesses { id: SignId, preprocesses: HashMap<Participant, Vec<u8>> },
+    Preprocesses {
+      id: SignId,
+      #[borsh(
+        serialize_with = "borsh_serialize_participant_map",
+        deserialize_with = "borsh_deserialize_participant_map"
+      )]
+      preprocesses: HashMap<Participant, Vec<u8>>,
+    },
     // Received shares for the specified signing protocol.
     ///
     /// This is sent by the Coordinator's Tributary scanner.
-    Shares { id: SignId, shares: HashMap<Participant, Vec<u8>> },
+    Shares {
+      id: SignId,
+      #[borsh(
+        serialize_with = "borsh_serialize_participant_map",
+        deserialize_with = "borsh_deserialize_participant_map"
+      )]
+      shares: HashMap<Participant, Vec<u8>>,
+    },
     // Re-attempt a signing protocol.
     ///
     /// This is sent by the Coordinator's Tributary re-attempt scheduling logic.
@@ -152,11 +226,24 @@ pub mod sign {
   #[derive(Clone, Debug, BorshSerialize, BorshDeserialize)]
   pub enum ProcessorMessage {
     // Participant sent an invalid message during the sign protocol.
-    InvalidParticipant { session: Session, participant: Participant },
+    InvalidParticipant {
+      session: Session,
+      #[borsh(
+        serialize_with = "borsh_serialize_participant",
+        deserialize_with = "borsh_deserialize_participant"
+      )]
+      participant: Participant,
+    },
     // Created preprocesses for the specified signing protocol.
-    Preprocesses { id: SignId, preprocesses: Vec<Vec<u8>> },
+    Preprocesses {
+      id: SignId,
+      preprocesses: Vec<Vec<u8>>,
+    },
     // Signed shares for the specified signing protocol.
-    Shares { id: SignId, shares: Vec<Vec<u8>> },
+    Shares {
+      id: SignId,
+      shares: Vec<Vec<u8>>,
+    },
   }
 }
 
@@ -301,7 +388,7 @@ impl CoordinatorMessage {
           }
           // Unique since one participation per participant per session
           key_gen::CoordinatorMessage::Participation { session, participant, .. } => {
-            (1, borsh::to_vec(&(session, participant)).unwrap())
+            (1, borsh::to_vec(&(session, u16::from(*participant))).unwrap())
           }
         };
 
@@ -372,7 +459,7 @@ impl ProcessorMessage {
           }
           // Unique since we only blame a participant once (as this is fatal)
           key_gen::ProcessorMessage::Blame { session, participant } => {
-            (2, borsh::to_vec(&(session, participant)).unwrap())
+            (2, borsh::to_vec(&(session, u16::from(*participant))).unwrap())
           }
         };