From b9df614591b28840994768a56a7c086a741b6f57 Mon Sep 17 00:00:00 2001
From: Brian Smith <brian@briansmith.org>
Date: Tue, 10 Dec 2024 16:21:53 -0800
Subject: [PATCH] ec/suite_b: Move `point_sum()` from `CommonOps` to
 `PrivateKeyOps`.

Internally, all the operations do use a single point addition
function (per curve) but that's an implementation detail of each
operation.
---
 src/ec/suite_b/ops.rs      | 11 +++++------
 src/ec/suite_b/ops/p256.rs |  5 ++---
 src/ec/suite_b/ops/p384.rs |  3 +--
 3 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/src/ec/suite_b/ops.rs b/src/ec/suite_b/ops.rs
index e8afb9f47..7c36c8a70 100644
--- a/src/ec/suite_b/ops.rs
+++ b/src/ec/suite_b/ops.rs
@@ -76,8 +76,6 @@ pub struct CommonOps {
     // In all cases, `r`, `a`, and `b` may all alias each other.
     elem_mul_mont: unsafe extern "C" fn(r: *mut Limb, a: *const Limb, b: *const Limb),
     elem_sqr_mont: unsafe extern "C" fn(r: *mut Limb, a: *const Limb),
-
-    point_add_jacobian_impl: unsafe extern "C" fn(r: *mut Limb, a: *const Limb, b: *const Limb),
 }
 
 impl CommonOps {
@@ -241,8 +239,8 @@ impl Modulus<Q> {
     }
 }
 
-impl CommonOps {
-    fn point_sum(&self, a: &Point, b: &Point, _cpu: cpu::Features) -> Point {
+impl PrivateKeyOps {
+    pub(super) fn point_sum(&self, a: &Point, b: &Point, _cpu: cpu::Features) -> Point {
         let mut r = Point::new_at_infinity();
         unsafe {
             (self.point_add_jacobian_impl)(r.xyz.as_mut_ptr(), a.xyz.as_ptr(), b.xyz.as_ptr())
@@ -290,6 +288,7 @@ pub struct PrivateKeyOps {
         p_x: *const Limb,      // [num_limbs]
         p_y: *const Limb,      // [num_limbs]
     ),
+    point_add_jacobian_impl: unsafe extern "C" fn(r: *mut Limb, a: *const Limb, b: *const Limb),
 }
 
 impl PrivateKeyOps {
@@ -486,7 +485,7 @@ fn twin_mul_inefficient(
 ) -> Point {
     let scaled_g = ops.point_mul_base(g_scalar, cpu);
     let scaled_p = ops.point_mul(p_scalar, p_xy, cpu);
-    ops.common.point_sum(&scaled_g, &scaled_p, cpu)
+    ops.point_sum(&scaled_g, &scaled_p, cpu)
 }
 
 // This assumes n < q < 2*n.
@@ -980,7 +979,7 @@ mod tests {
             let b = consume_jacobian_point(ops, test_case, "b");
             let r_expected: TestPoint<R> = consume_point(ops, test_case, "r");
 
-            let r_actual = ops.common.point_sum(&a, &b, cpu);
+            let r_actual = ops.point_sum(&a, &b, cpu);
             assert_point_actual_equals_expected(ops, &r_actual, &r_expected);
 
             Ok(())
diff --git a/src/ec/suite_b/ops/p256.rs b/src/ec/suite_b/ops/p256.rs
index 20ede07cc..61b14dda0 100644
--- a/src/ec/suite_b/ops/p256.rs
+++ b/src/ec/suite_b/ops/p256.rs
@@ -33,8 +33,6 @@ pub static COMMON_OPS: CommonOps = CommonOps {
 
     elem_mul_mont: p256_mul_mont,
     elem_sqr_mont: p256_sqr_mont,
-
-    point_add_jacobian_impl: p256_point_add,
 };
 
 #[cfg(test)]
@@ -48,6 +46,7 @@ pub static PRIVATE_KEY_OPS: PrivateKeyOps = PrivateKeyOps {
     elem_inv_squared: p256_elem_inv_squared,
     point_mul_base_impl: p256_point_mul_base_impl,
     point_mul_impl: p256_point_mul,
+    point_add_jacobian_impl: p256_point_add,
 };
 
 fn p256_elem_inv_squared(q: &Modulus<Q>, a: &Elem<R>) -> Elem<R> {
@@ -146,7 +145,7 @@ fn twin_mul_nistz256(
 ) -> Point {
     let scaled_g = point_mul_base_vartime(g_scalar, cpu);
     let scaled_p = PRIVATE_KEY_OPS.point_mul(p_scalar, p_xy, cpu::features());
-    PRIVATE_KEY_OPS.common.point_sum(&scaled_g, &scaled_p, cpu)
+    PRIVATE_KEY_OPS.point_sum(&scaled_g, &scaled_p, cpu)
 }
 
 #[cfg(any(target_arch = "aarch64", target_arch = "x86_64"))]
diff --git a/src/ec/suite_b/ops/p384.rs b/src/ec/suite_b/ops/p384.rs
index c4ab61a49..6950be987 100644
--- a/src/ec/suite_b/ops/p384.rs
+++ b/src/ec/suite_b/ops/p384.rs
@@ -33,8 +33,6 @@ pub static COMMON_OPS: CommonOps = CommonOps {
 
     elem_mul_mont: p384_elem_mul_mont,
     elem_sqr_mont: p384_elem_sqr_mont,
-
-    point_add_jacobian_impl: p384_point_add,
 };
 
 pub(super) static GENERATOR: (PublicElem<R>, PublicElem<R>) = (
@@ -47,6 +45,7 @@ pub static PRIVATE_KEY_OPS: PrivateKeyOps = PrivateKeyOps {
     elem_inv_squared: p384_elem_inv_squared,
     point_mul_base_impl: p384_point_mul_base_impl,
     point_mul_impl: p384_point_mul,
+    point_add_jacobian_impl: p384_point_add,
 };
 
 fn p384_elem_inv_squared(q: &Modulus<Q>, a: &Elem<R>) -> Elem<R> {