From: Chris Duncan <chris@zoso.dev>
Date: Sat, 19 Sep 2026 06:17:21 +0000 (-0700)
Subject: Clear static buffer after use to avoid leaveing the negated copy of the last base... 
X-Git-Url: https://git.codecow.com/?a=commitdiff_plain;h=b19957689ae414ef553c3767abaf8ca2345bde50;p=nano25519.git

Clear static buffer after use to avoid leaveing the negated copy of the last base table entry selected by the scalar since matching it against the 8 public entries recovers `|e[62]|`, the final radix-16 digit of the secret scalar.
---

diff --git a/src/assembly/ge.ts b/src/assembly/ge.ts
index dcbd51d..db4ed8b 100644
--- a/src/assembly/ge.ts
+++ b/src/assembly/ge.ts
@@ -31,7 +31,8 @@ function ge_cmov (t: ge_precomp, u: usize, b: u8): void {
 	fe_memcmov(changetype<usize>(t.xy2d), u + 96, b)
 }
 
-const minust = changetype<usize>(new StaticArray<i32>(36))
+/** Scratch array equivalent to a `ge_precomp`: 3x 12-limb FieldElements */
+const minust = new StaticArray<i32>(36)
 //@ts-expect-error
 @inline
 function ge_cmov8_base (t: ge_precomp, bp: usize, b: i8): void {
@@ -50,11 +51,12 @@ function ge_cmov8_base (t: ge_precomp, bp: usize, b: i8): void {
 	ge_cmov(t, bp += 144, equal(babs, 7))
 	ge_cmov(t, bp += 144, equal(babs, 8))
 
-	fe_memcopy(minust, changetype<usize>(t.yminusx))
-	fe_memcopy(minust + 48, changetype<usize>(t.yplusx))
-	fe_memneg(minust + 96, changetype<usize>(t.xy2d))
+	fe_memcopy(changetype<usize>(minust), changetype<usize>(t.yminusx))
+	fe_memcopy(changetype<usize>(minust) + 48, changetype<usize>(t.yplusx))
+	fe_memneg(changetype<usize>(minust) + 96, changetype<usize>(t.xy2d))
 
-	ge_cmov(t, minust, bnegative)
+	ge_cmov(t, changetype<usize>(minust), bnegative)
+	minust.fill(0)
 }
 
 const u: FieldElement = fe()