utils functionality moved to wrapper

Author: curiecrypt

mithril-stm/src/signature_scheme/schnorr_signature/jubjub_wrapper/curve_points.rs

@@ -1,6 +1,6 @@
 use anyhow::anyhow;
 use dusk_jubjub::{
-    AffinePoint as JubjubAffinePoint, ExtendedPoint as JubjubExtended,
+    AffinePoint as JubjubAffinePoint, EDWARDS_D, ExtendedPoint as JubjubExtended,
     SubgroupPoint as JubjubSubgroup,
 };
 use group::{Group, GroupEncoding};
@@ -17,10 +17,10 @@ impl AffinePoint {
     }
 
     pub(crate) fn from_prime_order_projective_point(
-        prime_order_projective_point: PrimeOrderProjectivePoint,
+        prime_order_projective_point: &PrimeOrderProjectivePoint,
     ) -> Self {
         AffinePoint(JubjubAffinePoint::from(
-            ProjectivePoint::from_prime_order_projective_point(prime_order_projective_point).0,
+            ProjectivePoint::from_prime_order_projective_point(*prime_order_projective_point).0,
         ))
     }
 
@@ -49,6 +49,12 @@ impl ProjectivePoint {
         ProjectivePoint(self.0 * scalar.0)
     }
 
+    pub(crate) fn get_coordinates(&self) -> (BaseFieldElement, BaseFieldElement) {
+        let affine_point = AffinePoint::from_projective_point(*self);
+
+        (affine_point.get_u(), affine_point.get_v())
+    }
+
     pub(crate) fn to_bytes(self) -> [u8; 32] {
         self.0.to_bytes()
     }
@@ -93,6 +99,29 @@ impl PrimeOrderProjectivePoint {
         PrimeOrderProjectivePoint(self.0 * scalar.0)
     }
 
+    /// Check if the given point is on the curve using its coordinates
+    pub(crate) fn is_on_curve(&self) -> StmResult<PrimeOrderProjectivePoint> {
+        let point_affine_representation = AffinePoint::from_prime_order_projective_point(self);
+        let (x, y) = (
+            point_affine_representation.get_u(),
+            point_affine_representation.get_v(),
+        );
+        let x_square = x.square();
+        let y_square = y.square();
+
+        let lhs = y_square.sub(&x_square);
+        let mut rhs = x_square.mul(&y_square);
+        rhs = rhs.mul(&BaseFieldElement(EDWARDS_D));
+        rhs = rhs.add(&BaseFieldElement::get_one());
+
+        if lhs != rhs {
+            return Err(anyhow!(SchnorrSignatureError::PointIsNotOnCurve(Box::new(
+                *self
+            ))));
+        }
+        Ok(*self)
+    }
+
     pub(crate) fn to_bytes(self) -> [u8; 32] {
         self.0.to_bytes()
     }

mithril-stm/src/signature_scheme/schnorr_signature/jubjub_wrapper/field_elements.rs

@@ -3,6 +3,7 @@ use dusk_jubjub::{Fq as JubjubBase, Fr as JubjubScalar};
 use ff::Field;
 use rand_core::{CryptoRng, RngCore};
 
+use super::ProjectivePoint;
 use crate::{StmResult, signature_scheme::SchnorrSignatureError};
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -28,6 +29,18 @@ impl BaseFieldElement {
     pub(crate) fn get_one() -> Self {
         BaseFieldElement(JubjubBase::ONE)
     }
+
+    pub(crate) fn collect_coordinates_of_list_of_points(
+        point_list: &[ProjectivePoint],
+    ) -> Vec<Self> {
+        let mut coordinates: Vec<BaseFieldElement> = Vec::new();
+        for point in point_list {
+            let (u, v) = point.get_coordinates();
+            coordinates.push(u);
+            coordinates.push(v);
+        }
+        coordinates
+    }
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]

mithril-stm/src/signature_scheme/schnorr_signature/mod.rs

@@ -2,14 +2,12 @@ mod error;
 mod jubjub_wrapper;
 mod signature;
 mod signing_key;
-mod utils;
 mod verification_key;
 
 pub use error::*;
 pub(crate) use jubjub_wrapper::*;
 pub use signature::*;
 pub use signing_key::*;
-pub(crate) use utils::*;
 pub use verification_key::*;
 
 #[cfg(test)]
@@ -18,15 +16,14 @@ mod tests {
     use rand_chacha::ChaCha20Rng;
     use rand_core::SeedableRng;
 
+    use super::{SchnorrSigningKey, SchnorrVerificationKey};
     use crate::{
         SchnorrSignature,
         signature_scheme::{PrimeOrderProjectivePoint, ScalarFieldElement, SchnorrSignatureError},
     };
 
-    use super::{SchnorrSigningKey, SchnorrVerificationKey};
-
     proptest! {
-            #![proptest_config(ProptestConfig::with_cases(10))]
+            #![proptest_config(ProptestConfig::with_cases(1000))]
 
             #[test]
             fn verification_key(seed in any::<[u8;32]>()) {

mithril-stm/src/signature_scheme/schnorr_signature/signature.rs

@@ -1,8 +1,8 @@
 use anyhow::{Context, anyhow};
 
 use super::{
-    PrimeOrderProjectivePoint, ProjectivePoint, ScalarFieldElement, SchnorrSignatureError,
-    SchnorrVerificationKey, collect_coordinates_of_list_of_points, compute_truncated_digest,
+    BaseFieldElement, PrimeOrderProjectivePoint, ProjectivePoint, ScalarFieldElement,
+    SchnorrSignatureError, SchnorrVerificationKey, compute_truncated_digest,
 };
 use crate::StmResult;
 
@@ -67,7 +67,7 @@ impl SchnorrSignature {
 
         // Since the hash function takes as input scalar elements
         // We need to convert the EC points to their coordinates
-        let points_coordinates = collect_coordinates_of_list_of_points(&[
+        let points_coordinates = BaseFieldElement::collect_coordinates_of_list_of_points(&[
             msg_hash_point,
             ProjectivePoint::from_prime_order_projective_point(verification_key.0),
             self.commitment_point,

mithril-stm/src/signature_scheme/schnorr_signature/signing_key.rs

@@ -2,9 +2,8 @@ use anyhow::{Context, anyhow};
 use rand_core::{CryptoRng, RngCore};
 
 use super::{
-    PrimeOrderProjectivePoint, ProjectivePoint, ScalarFieldElement, SchnorrSignature,
-    SchnorrSignatureError, SchnorrVerificationKey, collect_coordinates_of_list_of_points,
-    compute_truncated_digest,
+    BaseFieldElement, PrimeOrderProjectivePoint, ProjectivePoint, ScalarFieldElement,
+    SchnorrSignature, SchnorrSignatureError, SchnorrVerificationKey, compute_truncated_digest,
 };
 use crate::StmResult;
 
@@ -66,7 +65,7 @@ impl SchnorrSigningKey {
         // Since the hash function takes as input scalar elements
         // We need to convert the EC points to their coordinates
         // The order must be preserved
-        let points_coordinates = collect_coordinates_of_list_of_points(&[
+        let points_coordinates = BaseFieldElement::collect_coordinates_of_list_of_points(&[
             msg_hash_point,
             ProjectivePoint::from_prime_order_projective_point(verification_key.0),
             commitment_point,

mithril-stm/src/signature_scheme/schnorr_signature/utils.rs

@@ -1,10 +1,7 @@
 use anyhow::{Context, Ok, anyhow};
 
-use super::{PrimeOrderProjectivePoint, SchnorrSignatureError, SchnorrSigningKey};
-use crate::{
-    StmResult,
-    signature_scheme::{ProjectivePoint, is_on_curve},
-};
+use super::{PrimeOrderProjectivePoint, ProjectivePoint, SchnorrSignatureError, SchnorrSigningKey};
+use crate::StmResult;
 
 /// Schnorr verification key, it consists of a point on the Jubjub curve
 /// vk = g * sk, where g is a generator
@@ -35,7 +32,7 @@ impl SchnorrVerificationKey {
                 Box::new(self.0)
             )));
         }
-        is_on_curve(self.0)?;
+        self.0.is_on_curve()?;
 
         Ok(*self)
     }