From a9b96aa37ccca2fede045b1534fdb2e65b6045be Mon Sep 17 00:00:00 2001
From: Chris Duncan <chris@zoso.dev>
Date: Sun, 3 Aug 2025 03:44:40 -0700
Subject: [PATCH] Implement optimized square function for nacl.

---
 src/lib/nano-nacl.ts | 44 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 42 insertions(+), 2 deletions(-)

diff --git a/src/lib/nano-nacl.ts b/src/lib/nano-nacl.ts
index 789f52a..1840a11 100644
--- a/src/lib/nano-nacl.ts
+++ b/src/lib/nano-nacl.ts
@@ -139,7 +139,8 @@ export class NanoNaCl {
 	}
 
 	static Multiply (o: Float64Array, a: Float64Array, b: Float64Array): void {
-		let v, c, s = 1 << 16
+		let v, c
+		const s = 1 << 16
 		const t = new Array(31)
 		t.fill(0)
 
@@ -178,7 +179,46 @@ export class NanoNaCl {
 	}
 
 	static Square (o: Float64Array, a: Float64Array): void {
-		this.Multiply(o, a, a)
+		let v, c
+		const s = 1 << 16
+		const t = new Array(31)
+		t.fill(0)
+
+		// init t values, same as Multiply except we can skip some iterations of
+		// the inner loop since a[x]*a[y] + a[y]*a[x] = 2*a[x]*a[y]
+		for (let i = 0; i < 16; i++) {
+			for (let j = i; j < 16; j++) {
+				//@ts-expect-error
+				t[i + j] += a[i] * a[j] * ((i < j) + 1)
+			}
+		}
+
+		for (let i = 0; i < 15; i++) {
+			t[i] += 38 * t[i + 16]
+		}
+		// t15 left as is
+
+		// first carry
+		c = 1
+		for (let i = 0; i < 16; i++) {
+			v = t[i] + c + s - 1
+			c = Math.floor(v / s)
+			t[i] = v - c * s
+		}
+		t[0] += 38 * (c - 1)
+
+		// second carry
+		c = 1
+		for (let i = 0; i < 16; i++) {
+			v = t[i] + c + s - 1
+			c = Math.floor(v / s)
+			t[i] = v - c * s
+		}
+		t[0] += 38 * (c - 1)
+
+		// assign result to output
+		o.set(t.slice(0, 16), 0)
+		// this.Multiply(o, a, a)
 	}
 
 	static inv25519 (o: Float64Array, i: Float64Array): void {
-- 
2.47.3