add endpoints to vsss

Author: just-erray

src/circuit/mod.rs

@@ -137,16 +137,14 @@ impl StoredGates {
     pub fn save_to_json<P: AsRef<std::path::Path>>(&self, path: P) -> std::io::Result<()> {
         let file = std::fs::File::create(path)?;
         let writer = std::io::BufWriter::new(file);
-        serde_json::to_writer(writer, self)
-            .map_err(std::io::Error::other)
+        serde_json::to_writer(writer, self).map_err(std::io::Error::other)
     }
 
     /// Loads and deserializes stored gates from a JSON file.
     pub fn load_from_json<P: AsRef<std::path::Path>>(path: P) -> std::io::Result<Self> {
         let file = std::fs::File::open(path)?;
         let reader = std::io::BufReader::new(file);
-        serde_json::from_reader(reader)
-            .map_err(std::io::Error::other)
+        serde_json::from_reader(reader).map_err(std::io::Error::other)
     }
 }
 

src/cut_and_choose/vsss/core.rs

@@ -236,6 +236,13 @@ where
         }
         result
     }
+
+    /// Construct a polynomial from a list of point values evaluated at the
+    /// consecutive integer indices `0, 1, ..., degree`. The length of `points`
+    /// determines the degree (`degree = points.len() - 1`).
+    pub fn new(points: Vec<T>) -> Self {
+        Self(points)
+    }
 }
 
 impl Polynomial<Fr> {
@@ -323,6 +330,19 @@ impl ShareCommits<Projective> {
         Ok(())
     }
 
+    /// Verify that this [`ShareCommits`] is internally self-consistent, given
+    /// the degree of the underlying polynomial.
+    ///
+    /// The first `degree + 1` committed points are treated as the polynomial
+    /// coefficient commitments (`G * coeff[i]` for `i in 0..=degree`). A
+    /// [`PolynomialCommits`] is constructed from them and used to verify that
+    /// the remaining committed points are consistent via Lagrange interpolation.
+    pub fn verify_self_consistence(&self, degree: usize) -> Result<(), String> {
+        let poly = Polynomial::new(self.0[..=degree].to_vec());
+        let poly_commits = PolynomialCommits(poly);
+        self.verify(&poly_commits)
+    }
+
     pub fn verify_shares(&self, secp: &Secp256k1, shares: &[(usize, Fr)]) -> Result<(), String> {
         let mut indices = shares.iter().map(|(i, _)| *i).collect::<Vec<_>>();
         indices.sort_unstable();