From 85962c00a9b95e77a0d0a659321e2cc6b0e59a5a Mon Sep 17 00:00:00 2001
From: Luke Parker <lukeparker5132@gmail.com>
Date: Sun, 16 Oct 2022 09:42:33 -0400
Subject: [PATCH] Define a signature scheme trait

---
 substrate/tendermint/src/ext.rs   | 36 ++++++++++++++-------
 substrate/tendermint/tests/ext.rs | 54 +++++++++++++++++++++++--------
 2 files changed, 66 insertions(+), 24 deletions(-)

diff --git a/substrate/tendermint/src/ext.rs b/substrate/tendermint/src/ext.rs
index 642553c9..7e0f9ec3 100644
--- a/substrate/tendermint/src/ext.rs
+++ b/substrate/tendermint/src/ext.rs
@@ -12,18 +12,16 @@ pub struct BlockNumber(pub u32);
 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
 pub struct Round(pub u16);
 
-#[derive(Clone, Copy, PartialEq, Eq, Debug)]
-pub enum BlockError {
-  // Invalid behavior entirely
-  Fatal,
-  // Potentially valid behavior dependent on unsynchronized state
-  Temporal,
-}
+pub trait SignatureScheme {
+  type ValidatorId: ValidatorId;
+  type Signature: Clone + Copy + PartialEq;
+  type AggregateSignature: Clone + PartialEq;
 
-pub trait Block: Send + Sync + Clone + PartialEq + Debug {
-  type Id: Send + Sync + Copy + Clone + PartialEq + Debug;
-
-  fn id(&self) -> Self::Id;
+  fn sign(&self, msg: &[u8]) -> Self::Signature;
+  #[must_use]
+  fn verify(&self, validator: Self::ValidatorId, msg: &[u8], sig: Self::Signature) -> bool;
+  // Intended to be a BLS signature, a Schnorr signature half-aggregation, or a Vec<Signature>.
+  fn aggregate(signatures: &[Self::Signature]) -> Self::AggregateSignature;
 }
 
 pub trait Weights: Send + Sync {
@@ -42,15 +40,31 @@ pub trait Weights: Send + Sync {
   fn proposer(&self, number: BlockNumber, round: Round) -> Self::ValidatorId;
 }
 
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+pub enum BlockError {
+  // Invalid behavior entirely
+  Fatal,
+  // Potentially valid behavior dependent on unsynchronized state
+  Temporal,
+}
+
+pub trait Block: Send + Sync + Clone + PartialEq + Debug {
+  type Id: Send + Sync + Copy + Clone + PartialEq + Debug;
+
+  fn id(&self) -> Self::Id;
+}
+
 #[async_trait::async_trait]
 pub trait Network: Send + Sync {
   type ValidatorId: ValidatorId;
+  type SignatureScheme: SignatureScheme;
   type Weights: Weights<ValidatorId = Self::ValidatorId>;
   type Block: Block;
 
   // Block time in seconds
   const BLOCK_TIME: u32;
 
+  fn signature_scheme(&self) -> Arc<Self::SignatureScheme>;
   fn weights(&self) -> Arc<Self::Weights>;
 
   async fn broadcast(&mut self, msg: Message<Self::ValidatorId, Self::Block>);
diff --git a/substrate/tendermint/tests/ext.rs b/substrate/tendermint/tests/ext.rs
index ce15507f..5846b8fc 100644
--- a/substrate/tendermint/tests/ext.rs
+++ b/substrate/tendermint/tests/ext.rs
@@ -7,17 +7,25 @@ use tendermint_machine::{ext::*, Message, TendermintMachine, TendermintHandle};
 type TestValidatorId = u16;
 type TestBlockId = u32;
 
-#[derive(Clone, PartialEq, Debug)]
-struct TestBlock {
-  id: TestBlockId,
-  valid: Result<(), BlockError>,
-}
+struct TestSignatureScheme(u16);
+impl SignatureScheme for TestSignatureScheme {
+  type ValidatorId = TestValidatorId;
+  type Signature = [u8; 32];
+  type AggregateSignature = Vec<[u8; 32]>;
 
-impl Block for TestBlock {
-  type Id = TestBlockId;
+  fn sign(&self, msg: &[u8]) -> [u8; 32] {
+    let mut sig = [0; 32];
+    sig[.. 2].copy_from_slice(&self.0.to_le_bytes());
+    sig[2 .. (2 + 30.min(msg.len()))].copy_from_slice(msg);
+    sig
+  }
 
-  fn id(&self) -> TestBlockId {
-    self.id
+  fn verify(&self, validator: u16, msg: &[u8], sig: [u8; 32]) -> bool {
+    (sig[.. 2] == validator.to_le_bytes()) && (&sig[2 ..] == &[msg, &[0; 30]].concat()[.. 30])
+  }
+
+  fn aggregate(sigs: &[[u8; 32]]) -> Vec<[u8; 32]> {
+    sigs.to_vec()
   }
 }
 
@@ -37,22 +45,41 @@ impl Weights for TestWeights {
   }
 }
 
-struct TestNetwork(Arc<RwLock<Vec<TendermintHandle<Self>>>>);
+#[derive(Clone, PartialEq, Debug)]
+struct TestBlock {
+  id: TestBlockId,
+  valid: Result<(), BlockError>,
+}
+
+impl Block for TestBlock {
+  type Id = TestBlockId;
+
+  fn id(&self) -> TestBlockId {
+    self.id
+  }
+}
+
+struct TestNetwork(u16, Arc<RwLock<Vec<TendermintHandle<Self>>>>);
 
 #[async_trait::async_trait]
 impl Network for TestNetwork {
   type ValidatorId = TestValidatorId;
+  type SignatureScheme = TestSignatureScheme;
   type Weights = TestWeights;
   type Block = TestBlock;
 
   const BLOCK_TIME: u32 = 1;
 
+  fn signature_scheme(&self) -> Arc<TestSignatureScheme> {
+    Arc::new(TestSignatureScheme(self.0))
+  }
+
   fn weights(&self) -> Arc<TestWeights> {
     Arc::new(TestWeights)
   }
 
   async fn broadcast(&mut self, msg: Message<TestValidatorId, Self::Block>) {
-    for handle in self.0.write().await.iter_mut() {
+    for handle in self.1.write().await.iter_mut() {
       handle.messages.send(msg.clone()).await.unwrap();
     }
   }
@@ -79,9 +106,10 @@ impl TestNetwork {
     {
       let mut write = arc.write().await;
       for i in 0 .. validators {
+        let i = u16::try_from(i).unwrap();
         write.push(TendermintMachine::new(
-          TestNetwork(arc.clone()),
-          u16::try_from(i).unwrap(),
+          TestNetwork(i, arc.clone()),
+          i,
           BlockNumber(1),
           TestBlock { id: 1, valid: Ok(()) },
         ));