rearrange code - nonce_gen impl SignSession order

Author: nickfarrow

schnorr_fun/src/frost.rs

@@ -730,17 +730,39 @@ impl<H: Digest<OutputSize = U32> + Clone, NG> Frost<H, NG> {
     }
 }
 
-/// Calculate the lagrange coefficient for participant with index x_j and other signers indexes x_ms
-fn lagrange_lambda(x_j: u32, x_ms: &[u32]) -> Scalar {
-    let x_j = Scalar::from(x_j).expect_nonzero("target xcoord can not be zero");
-    x_ms.iter()
-        .map(|x_m| Scalar::from(*x_m).expect_nonzero("index can not be zero"))
-        .fold(Scalar::one(), |acc, x_m| {
-            let denominator = s!(x_m - x_j)
-                .expect_nonzero("removed duplicate indexes")
-                .invert();
-            s!(acc * x_m * denominator)
-        })
+impl<H: Digest<OutputSize = U32> + Clone, NG: NonceGen> Frost<H, NG> {
+    /// Generate nonces for secret shares
+    ///
+    /// This method should be used carefully.
+    /// This calls [`NonceKeyPair::generate`] internally with the frost instance's [`NonceGen`].
+    /// See documentation for that for more usage info.
+    ///
+    /// When choosing a `secret` to use, if you are generating nonces prior to [`KeyGen`] completion,
+    /// use the static first coefficient of your polynomial.
+    /// Otherwise you can use your secret share of the frost key.
+    ///
+    /// The application must decide upon a unique `sid` for this frost multisignature.
+    /// For example, the concatenation of: my_signing_index, verfication_shares, purpose
+    ///
+    /// ## Return Value
+    ///
+    /// A NonceKeyPair comprised of secret scalars [r1, r2] and public nonces [R1, R2]
+    /// [`NonceKeyPair::generate`]: crate::binonce::NonceKeyPair::generate
+    pub fn gen_nonce(
+        &self,
+        secret: &Scalar,
+        session_id: &[u8],
+        public_key: Option<Point>,
+        message: Option<Message<'_>>,
+    ) -> NonceKeyPair {
+        NonceKeyPair::generate(
+            self.schnorr.nonce_gen(),
+            secret,
+            session_id,
+            public_key,
+            message,
+        )
+    }
 }
 
 /// A FROST signing session
@@ -768,6 +790,19 @@ impl SignSession {
     }
 }
 
+/// Calculate the lagrange coefficient for participant with index x_j and other signers indexes x_ms
+fn lagrange_lambda(x_j: u32, x_ms: &[u32]) -> Scalar {
+    let x_j = Scalar::from(x_j).expect_nonzero("target xcoord can not be zero");
+    x_ms.iter()
+        .map(|x_m| Scalar::from(*x_m).expect_nonzero("index can not be zero"))
+        .fold(Scalar::one(), |acc, x_m| {
+            let denominator = s!(x_m - x_j)
+                .expect_nonzero("removed duplicate indexes")
+                .invert();
+            s!(acc * x_m * denominator)
+        })
+}
+
 impl<H: Digest<OutputSize = U32> + Clone, NG> Frost<H, NG> {
     /// Start a FROST signing session.
     ///
@@ -937,41 +972,6 @@ impl<H: Digest<OutputSize = U32> + Clone, NG> Frost<H, NG> {
     }
 }
 
-impl<H: Digest<OutputSize = U32> + Clone, NG: NonceGen> Frost<H, NG> {
-    /// Generate nonces for secret shares
-    ///
-    /// This method should be used carefully.
-    /// This calls [`NonceKeyPair::generate`] internally with the frost instance's [`NonceGen`].
-    /// See documentation for that for more usage info.
-    ///
-    /// When choosing a `secret` to use, if you are generating nonces prior to [`KeyGen`] completion,
-    /// use the static first coefficient of your polynomial.
-    /// Otherwise you can use your secret share of the frost key.
-    ///
-    /// The application must decide upon a unique `sid` for this frost multisignature.
-    /// For example, the concatenation of: my_signing_index, verfication_shares, purpose
-    ///
-    /// ## Return Value
-    ///
-    /// A NonceKeyPair comprised of secret scalars [r1, r2] and public nonces [R1, R2]
-    /// [`NonceKeyPair::generate`]: crate::binonce::NonceKeyPair::generate
-    pub fn gen_nonce(
-        &self,
-        secret: &Scalar,
-        session_id: &[u8],
-        public_key: Option<Point>,
-        message: Option<Message<'_>>,
-    ) -> NonceKeyPair {
-        NonceKeyPair::generate(
-            self.schnorr.nonce_gen(),
-            secret,
-            session_id,
-            public_key,
-            message,
-        )
-    }
-}
-
 #[cfg(test)]
 mod test {
     use core::num::NonZeroU32;