Simplify (#906)

* simplify

* Simplify

* More

* Misc fixes + simplify FS impl

* clippy

Author: jonas-lj

fastcrypto-tbls/src/threshold_schnorr/avss.rs

@@ -312,10 +312,10 @@ impl Receiver {
             &self.random_oracle(),
             |shares: &SharesForNode| shares.verify(message),
         )?;
-        Ok(ComplaintResponse::create(
-            self.id,
-            my_output.my_shares.clone(),
-        ))
+        Ok(ComplaintResponse {
+            responder_id: self.id,
+            shares: my_output.my_shares.clone(),
+        })
     }
 
     /// 5. Upon receiving t valid responses to a complaint, the accuser can recover its shares.

fastcrypto-tbls/src/threshold_schnorr/batch_avss.rs

@@ -108,7 +108,7 @@ impl<const BATCH_SIZE: usize> ShareBatch<BATCH_SIZE> {
             .iter()
             .zip(challenge)
             .fold(self.blinding_share, |acc, (r_l, gamma_l)| {
-                acc + (*r_l * gamma_l)
+                acc + r_l * gamma_l
             })
             != message.response_polynomial.eval(self.index).value
         {
@@ -407,10 +407,10 @@ impl Receiver {
             &self.random_oracle(),
             |shares: &SharesForNode<BATCH_SIZE>| shares.verify(&self.random_oracle(), message),
         )?;
-        Ok(ComplaintResponse::create(
-            self.id,
-            my_output.my_shares.clone(),
-        ))
+        Ok(ComplaintResponse {
+            responder_id: self.id,
+            shares: my_output.my_shares.clone(),
+        })
     }
 
     /// 5. Upon receiving t valid responses to a complaint, the accuser can recover its shares.

fastcrypto-tbls/src/threshold_schnorr/complaint.rs

@@ -40,32 +40,26 @@ impl Complaint {
             self.accuser_id as usize,
         )?;
 
-        let shares = match S::from_bytes(&buffer) {
-            Ok(s) => s,
-            Err(_) => {
-                debug!(
-                    "Complaint by party {} is valid: C complaint failed to deserialize shares",
-                    self.accuser_id
-                );
-                return Ok(());
-            }
+        let Ok(shares) = S::from_bytes(&buffer) else {
+            debug!(
+                "Complaint by party {} is valid: Failed to deserialize shares",
+                self.accuser_id
+            );
+            return Ok(());
         };
 
-        match verifier(&shares) {
-            Ok(_) => {
-                debug!(
-                    "Complaint by party {} is invalid: Shares verify correctly",
-                    self.accuser_id
-                );
-                Err(InvalidProof)
-            }
-            Err(_) => {
-                debug!(
-                    "Complaint by party {} is valid: Shares do not verify correctly",
-                    self.accuser_id
-                );
-                Ok(())
-            }
+        if verifier(&shares).is_ok() {
+            debug!(
+                "Complaint by party {} is invalid: Shares verify correctly",
+                self.accuser_id
+            );
+            Err(InvalidProof)
+        } else {
+            debug!(
+                "Complaint by party {} is valid: Shares do not verify correctly",
+                self.accuser_id
+            );
+            Ok(())
         }
     }
 
@@ -93,12 +87,3 @@ pub struct ComplaintResponse<S> {
     pub(crate) responder_id: PartyId,
     pub(crate) shares: S,
 }
-
-impl<S> ComplaintResponse<S> {
-    pub(crate) fn create(responder_id: PartyId, shares: S) -> Self {
-        ComplaintResponse {
-            responder_id,
-            shares,
-        }
-    }
-}

fastcrypto-tbls/src/threshold_schnorr/pascal_matrix.rs

@@ -67,7 +67,7 @@ impl<C: GroupElement> LazyPascalMatrixMultiplier<C> {
     /// Create a new lazy Pascal matrix iterator that will yield `height * columns.len()` elements.
     /// Panics if
     /// * `columns` is empty,
-    /// * if the columns are not all of the same length which is at least `height`,
+    /// * if the columns are not all of the same length that is at least `height`,
     /// * if `height` is zero.
     pub fn new(height: usize, columns: Vec<Vec<C>>) -> Self {
         assert!(!columns.is_empty());
@@ -93,18 +93,12 @@ impl<C: GroupElement> Iterator for LazyPascalMatrixMultiplier<C> {
     type Item = C;
 
     fn next(&mut self) -> Option<Self::Item> {
-        match self.current_vector.next() {
-            Some(v) => Some(v),
-            None => {
-                if self.buffers.is_empty() {
-                    None
-                } else {
-                    self.current_vector =
-                        LazyPascalVectorMultiplier::new(self.height, self.buffers.pop().unwrap());
-                    self.current_vector.next()
-                }
-            }
-        }
+        self.current_vector.next().or_else(|| {
+            self.buffers.pop().and_then(|v| {
+                self.current_vector = LazyPascalVectorMultiplier::new(self.height, v);
+                self.next()
+            })
+        })
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {

fastcrypto/src/groups/secp256k1.rs

@@ -7,7 +7,6 @@ use crate::error::{FastCryptoError, FastCryptoResult};
 use crate::groups::{
     Doubling, FiatShamirChallenge, GroupElement, MultiScalarMul, Scalar as ScalarTrait,
 };
-use crate::hash::{HashFunction, Sha3_512};
 use crate::serde_helpers::ToFromByteArray;
 use crate::serialize_deserialize_with_to_from_byte_array;
 use crate::traits::AllowedRng;
@@ -257,9 +256,9 @@ impl ToFromByteArray<SCALAR_SIZE_IN_BYTES> for Scalar {
 
 impl FiatShamirChallenge for Scalar {
     fn fiat_shamir_reduction_to_group_element(uniform_buffer: &[u8]) -> Self {
-        Scalar::from(Fr::from_be_bytes_mod_order(
-            &Sha3_512::digest(uniform_buffer).digest,
-        ))
+        // Ensure that we have enough bytes to avoid bias in the modular reduction.
+        assert!(uniform_buffer.len() >= 48);
+        Scalar::from(Fr::from_be_bytes_mod_order(uniform_buffer))
     }
 }