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[ed25519] implement add for SW form (#55)

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* impl add for SW

* Update short_weierstrass.rs
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zz-sol 2026-06-18 07:32:25 -04:00 committed by GitHub
parent dd4164eefe
commit 34e36a7c32
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1 changed files with 27 additions and 0 deletions
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27
curve25519/solana-ed25519/src/short_weierstrass.rs
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@ -3,6 +3,8 @@
//! This module provides a lightweight affine representation and conversion
//! utilities for moving between the Edwards and short Weierstrass models.
use core::ops::Add;
use crate::edwards::EdwardsPoint;
use crate::field::FieldElement;
use crate::traits::{Identity, IsIdentity};
@ -164,6 +166,16 @@ impl SwPoint {
}
}
impl<'a> Add<&'a SwPoint> for &SwPoint {
type Output = SwPoint;
fn add(self, other: &'a SwPoint) -> SwPoint {
SwPoint::add(self, other)
}
}
define_add_variants!(LHS = SwPoint, RHS = SwPoint, Output = SwPoint);
fn affine_coordinates_on_curve(x: &FieldElement, y: &FieldElement) -> bool {
let y2 = y.square();
let x2 = x.square();
@ -266,6 +278,21 @@ mod tests {
Scalar::from_bytes_mod_order_wide(&wide)
}
#[test]
fn sw_add_operator_matches_inherent_add() {
let p = SwPoint::from_edwards(&constants::ED25519_BASEPOINT_POINT);
let q = SwPoint::from_edwards(&(constants::ED25519_BASEPOINT_POINT * Scalar::from(7u64)));
let expected = p.add(&q);
assert_eq!(
<&SwPoint as core::ops::Add<&SwPoint>>::add(&p, &q),
expected
);
assert_eq!(<SwPoint as core::ops::Add<&SwPoint>>::add(p, &q), expected);
assert_eq!(<&SwPoint as core::ops::Add<SwPoint>>::add(&p, q), expected);
assert_eq!(<SwPoint as core::ops::Add<SwPoint>>::add(p, q), expected);
}
#[test]
fn sw_round_trip_add_matches_edwards() {
let mut rng = rand::thread_rng();