zig

commit 1bf29757d963b301c1fcfccb9b39b277381de115 (tree)
parent 4cee1f7b9a6df9c890268eddc526e66dfa16f0ad
Author: jedisct1 <jedisct1@noreply.codeberg.org>
Date:   Fri,  2 Jan 2026 23:37:12 +0100

Merge pull request 'crypto.edwards25519: optimize rejectLowOrder' (#30650) from jedisct1/zig:ed25519rej into master

Reviewed-on: https://codeberg.org/ziglang/zig/pulls/30650

Diffstat:
M
lib/std/crypto/25519/edwards25519.zig
 | 
10
++++------

1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/lib/std/crypto/25519/edwards25519.zig b/lib/std/crypto/25519/edwards25519.zig
@@ -127,12 +127,10 @@ pub const Edwards25519 = struct {
     /// Check that the point does not generate a low-order group.
     /// Return a `WeakPublicKey` error if it does.
     pub fn rejectLowOrder(p: Edwards25519) WeakPublicKeyError!void {
-        const zi = p.z.invert();
-        const x = p.x.mul(zi);
-        const y = p.y.mul(zi);
-        const x_neg = x.neg();
-        const iy = Fe.sqrtm1.mul(y);
-        if (x.isZero() or y.isZero() or iy.equivalent(x) or iy.equivalent(x_neg)) {
+        const y_sqrtm1 = Fe.sqrtm1.mul(p.y);
+        if (p.x.isZero() or p.y.isZero() or p.z.isZero() or
+            y_sqrtm1.sub(p.x).isZero() or y_sqrtm1.add(p.x).isZero())
+        {
             return error.WeakPublicKey;
         }
     }