Apply suggestions from review

Author: iquerejeta

mithril-aggregator/src/multi_signer.rs

@@ -36,6 +36,10 @@ pub enum ProtocolError {
     #[error("signer already registered")]
     ExistingSigner(),
 
+    /// Signer was not registered.
+    #[error("signer did not register")]
+    UnregisteredParty(),
+
     /// Signer registration failed.
     #[error("signer registration failed")]
     FailedSignerRegistration(#[from] ProtocolRegistrationError),
@@ -710,40 +714,35 @@ impl MultiSigner for MultiSignerImpl {
 
         // If there is no reg_party, then we simply received a signature from a non-registered
         // party, and we can ignore the request.
-        if let Some((vk, stake)) = clerk.get_reg_party(&signature.signer_index) {
-            signature
-                .verify(
-                    &protocol_parameters,
-                    &vk,
-                    &stake,
-                    &avk,
-                    message.compute_hash().as_bytes(),
-                )
-                .map_err(|e| ProtocolError::Core(e.to_string()))?;
+        let (vk, stake) = clerk
+            .get_reg_party(&signature.signer_index)
+            .ok_or_else(ProtocolError::UnregisteredParty)?;
+        signature
+            .verify(
+                &protocol_parameters,
+                &vk,
+                &stake,
+                &avk,
+                message.compute_hash().as_bytes(),
+            )
+            .map_err(|e| ProtocolError::Core(e.to_string()))?;
 
-            // Register single signature
-            let beacon = self
-                .current_beacon
-                .as_ref()
-                .ok_or_else(ProtocolError::UnavailableBeacon)?;
-
-            match self
-                .single_signature_store
-                .save_single_signatures(beacon, signatures)
-                .await?
-            {
-                Some(_) => {
-                    return Err(ProtocolError::ExistingSingleSignature(
-                        signatures.party_id.clone(),
-                    ));
-                }
-                None => {
-                    return Ok(());
-                }
-            }
-        }
+        // Register single signature
+        let beacon = self
+            .current_beacon
+            .as_ref()
+            .ok_or_else(ProtocolError::UnavailableBeacon)?;
 
-        Ok(())
+        return match self
+            .single_signature_store
+            .save_single_signatures(beacon, signatures)
+            .await?
+        {
+            Some(_) => Err(ProtocolError::ExistingSingleSignature(
+                signatures.party_id.clone(),
+            )),
+            None => Ok(()),
+        };
     }
 
     /// Retrieves a multi signature from a message

mithril-stm/README.md

@@ -143,7 +143,7 @@ fn main() {
 
 Here we give the benchmark results of STM for size and time. We run the benchmarks on macOS 12.6 on an Apple M1 Pro machine with 16 GB of RAM.
 
-Note that the size of an individual signature with one valid index is **176 bytes** and increases linearly in the length of valid indices (where an index is 8 bytes).
+Note that the size of an individual signature with one valid index is **72 bytes** (48 bytes from `sigma`, 8 bytes from `party_index`, 8 bytes for the `length` of winning indices and at least 8 bytes for a single winning `index`) and increases linearly in the length of valid indices (where an index is 8 bytes).
 
 ```shell
 +----------------------+

mithril-stm/src/stm.rs

@@ -558,7 +558,10 @@ impl<D: Digest + Clone + FixedOutput> StmClerk<D> {
 
     /// Get the (VK, stake) of a party given its index.
     pub fn get_reg_party(&self, party_index: &Index) -> Option<(StmVerificationKey, Stake)> {
-       self.closed_reg.reg_parties.get(*party_index as usize).map(|r| r.into())
+        self.closed_reg
+            .reg_parties
+            .get(*party_index as usize)
+            .map(|&r| r.into())
     }
 }